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Vaccination: Cornerstone of Influenza Control

Benefits of influenza vaccination

The value of immunization against influenza is sometimes being questioned, as outbreaks of flu continue despite increased influenza vaccination coverage. 39 x DS Fedson, K Nichol. Should we question the benefits of influenza vaccination for elderly people? Infectious Disease News, Guest Editorial. (www.infectiousdiseasenews.com/200508/guested1.asp) (August 2005) Therefore, there has been a strong demand for sound scientific data on the effects of influenza vaccination. As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination. 12, x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. 13, x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) 33, x T Heikkinen, R Booy, M Campins, et al.. Should healthy children be vaccinated against influenza? A consensus report of the Summits of Independent European Vaccination Experts. Eur J Pediatr 21 (2005) (1 - 6) 35, x YZ Ghendon, AN Kaira, GA Elshina. The effect of mass influenza immunization in children on the morbidity of the unvaccinated elderly. Epidemiol Infect 134 (2006) (71 - 78) 40 x AC Voordouw, MC Sturkenboom, JP Dieleman, et al.. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. J Am Med Assoc 292 (2004) (2089 - 2095) Crossref. Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below. Individual studies have also indicated clear-cut beneficial effects in other target groups, such as diabetics 37 x SA Smith, GA Poland. The use of influenza and pneumococcal vaccines in people with diabetes (technical review). Diabetes Care 23 (2000) (95 - 108) Crossref. and patients with asthma 41 x SA Harper, K Fukuda, TM Uyeki, et al.. Advisory Committee on Immunization Practices (ACIP), Centers for Disease Control and Prevention (CDC). Prevention and control of influenza. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 54 (RR-8) (2005) (1 - 40) or cardiovascular disease. 42 x KL Nichol, J Nordin, J Mullooly, et al.. Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly. New Engl J Med 348 (2003) (1322 - 1332) Crossref.

Vaccine efficacy and clinical effectiveness of influenza vaccination

In evaluating the outcome of influenza vaccination, a distinction is often made between vaccine efficacy per se and the clinical effectiveness of vaccination. 12, x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. 13 x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) Vaccine efficacy is defined as the reduction in the rate of laboratory-confirmed influenza among vaccinated compared to non-vaccinated individuals. Vaccine efficacy thus provides a direct measure of the specific reduction in influenza infection rates as a result of the vaccination. With an approximate annual attack rate of influenza of 5–10%, accurate determination of vaccine efficacy requires well-controlled studies and evaluation of large study groups. Obviously, vaccine efficacy will depend critically on the match between the vaccine composition and the circulating virus strains.

Clinical effectiveness provides a less specific, yet quite relevant and important, measure of the benefit of influenza vaccination. It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes. 12, x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. 13, x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) 40 x AC Voordouw, MC Sturkenboom, JP Dieleman, et al.. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. J Am Med Assoc 292 (2004) (2089 - 2095) Crossref. As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28 . 13 x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.

Figure 28 Relationship between influenza vaccine efficacy and clinical effectiveness of influenza vaccination. The figure shows a hypothetical example in which vaccination is associated with a 35% reduction in all outcomes evaluated (such as hospitalizations for pneumonia). However, not all outcomes are due to influenza. If only 40% of the outcomes represented complications of influenza, the underlying efficacy of the vaccine preventing direct influenza-associated outcomes would be 35%/0.4 = 87.5%. source: Adapted from Nichol KL. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. In: Nicholson KG, Webster RG, Hay AJ, editors. Textbook of Influenza. Blackwell Science, 1998; pp. 358–372 13 x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) with permission from Blackwell Publishing.

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References in context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
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Because of the non-specific criteria of influenza-like illness (ILI), the outcome of clinical effectiveness studies depends on the used case definition in the particular study. Indeed, applying different case definitions to one data set from a single clinical study resulted in very different study outcomes. 43 x KL Nichol, P Mendelman. Influence of clinical case definitions with differing levels of sensitivity and specificity on estimates of the relative and absolute health benefits of influenza vaccination among healthy working adults and implications for economic analyses. Virus Res 103 (2004) (3 - 8) Crossref. A recent literature review revealed that all published clinical effectiveness studies applied different case definitions for ILI 44 x WEP Beyer. Heterogeneity of case-definitions used in vaccine effectiveness studies and its impact on meta-analysis. Vaccine (2006) in press. and that by simply changing the sensitivity and specificity of case definitions and observation periods, differences of as much as 30% in study outcome for vaccination effectiveness may be found. Therefore, it was recommended that internationally agreed case definitions for ILI should be developed, as well as observational periods for future influenza clinical effectiveness studies. In recent systematic reviews (Cochrane) on influenza vaccination effectiveness in healthy adults 45 x V Demicheli, D Rivetti, JJ Deeks, et al.. Vaccines for preventing influenza in healthy adults. Cochrane Database Syst Rev 3 (2004) CD001269 Review. and children, 46 x T Jefferson, S Smith, V Demicheli, et al.. Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet 365 (2005) (773 - 780) literature data were pooled for the review process, but the differences in case definitions of individual studies were not taken into account. Because of this methodological problem, interpretation of such combined vaccination effectiveness estimates should be made with caution. 34, x T Heikkinen, O Ruuskanen. Influenza vaccines in healthy children (letter to the editor). Lancet 365 (2005) (2086 - 2087) Crossref. 44 x WEP Beyer. Heterogeneity of case-definitions used in vaccine effectiveness studies and its impact on meta-analysis. Vaccine (2006) in press. Clearly, these considerations are also relevant for health-economic analyses of influenza vaccination programmes. 47 x K Nichol, J Nordin, J Mullooly. Influence of clinical outcome and outcome period definitions on estimates of absolute clinical and economic benefits of influenza vaccination in community dwelling elderly persons. Vaccine 24 (2006) (1562 - 1568) Crossref.

Health benefits of vaccination of the elderly

Several studies have indicated that, in cases of a good match between vaccine strain and circulating virus, the efficacy of current inactivated influenza vaccines among the elderly is approximately 60%. For example, in a large, randomized, double-blind, placebo-controlled trial among 1838 subjects of 60 years of age or older in the Netherlands, vaccine efficacy was found to be 58%. 48 x TME Govaert, CTMCN Thijs, N Masurel, et al.. The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial. J Am Med Assoc 272 (1994) (1661 - 1665) This trial was conducted in the 1991–92 winter season and involved the use of a multivalent inactivated influenza vaccine, matching well with the circulating virus.

Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly. 12, x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. 13, x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) 40, x AC Voordouw, MC Sturkenboom, JP Dieleman, et al.. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. J Am Med Assoc 292 (2004) (2089 - 2095) Crossref. 48, x TME Govaert, CTMCN Thijs, N Masurel, et al.. The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial. J Am Med Assoc 272 (1994) (1661 - 1665) 49 x KL Nichol. Influenza vaccination in the elderly. Impact on hospitalization and mortality. Drugs Aging 22 (2005) (495 - 515) Crossref. For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population. The vaccination was associated with significant reductions in pneumonia (29–32%), cardiac disease (19%) and cerebrovascular disease (16–23%). 42 x KL Nichol, J Nordin, J Mullooly, et al.. Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly. New Engl J Med 348 (2003) (1322 - 1332) Crossref. Other studies have indicated that influenza vaccination of patients who have had a myocardial infarction results in a significant reduction in 1-year mortality rates (66% reduction) or risk of further ischaemic events. A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly ( Table 18 ). 50 x T Vu, S Farish, M Jenkins, H Kelly. A meta-analysis of effectiveness of influenza vaccine in persons aged 65 years and over living in the community. Vaccine 20 (2002) (1831 - 1836) Crossref. Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes ( Table 18 ). 51 x PA Gross, AW Hermogenes, HS Sachs, J Lau, RA Levandowski. The efficacy of influenza vaccine in elderly persons: a meta-analysis and review of the literature. Ann Intern Med 123 (1995) (518 - 527) These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.

Table 18 Clinical effectiveness of influenza vaccination of the elderly. source: Adapted from Nichol KL. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 2003; 21: 1769–1775 12 x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. with permission from Elsevier.

Clinical effectiveness of influenza vaccination of the elderly
Outcome measure Reduction
Community-dwelling senior citizens
Hospitalizations for
 Pneumonia from all causes 33%
 All respiratory conditions 32%
 Congestive heart failure 27%
Death from all causes 50%
Elderly in nursing homes
Respiratory illness 56%
Pneumonia from all causes 53%
Hospitalization in general 48%
Death from all causes 68%

References in context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context

Cost-effectiveness of vaccination of the elderly

Economic evaluations, conducted in many different countries, have indicated that vaccination of senior citizens against influenza is always cost-effective and frequently cost-saving. 12, x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. 13 x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) For example, in a 6-year study carried out in Minnesota, USA, influenza vaccination of nursing-home residents was associated with an average net saving of $73 per person as a result of reductions in direct medical costs. 12 x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. Vaccination appears to be cost-effective or even cost-saving for both healthy senior citizens and high-risk elderly with underlying chronic medical conditions. In a study conducted in the Netherlands in the 1995–96 and 1997–98 seasons, influenza vaccination was found to be cost-saving for high-risk elderly and cost-effective for all elderly and elderly at low risk, the cost-effectiveness ratios being &z.euro;1820 per life-year gained for all elderly and &z.euro;6900 per life-year gained for those at low risk. 52 x MJ Postma, JM Bos, M Van Gennip, et al.. Economic evaluation of influenza vaccination. Assessment for The Netherlands. Pharmacoeconomics 16 (Suppl 1) (1999) (33 - 40) Crossref. Similar studies have been conducted in other countries with similar outcomes.

Vaccine safety and contraindications

Inactivated influenza vaccines have an excellent safety record. 9, x World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 75 (2000) (281 - 288) 14 x MJ Wiselka. Vaccine safety. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (346 - 357) Currently, about 300 million vaccine doses are being administered annually around the globe, 10 x The Macroepidemiology of Influenza Vaccination (MIV) Study Group. The macroepidemiology of influenza vaccination in 56 countries, 1997–2003. Vaccine 23 (2005) (5133 - 5143) and the overall rate of adverse reactions is extremely low. However, sporadically, adverse reactions do occur. The most frequently occurring side effects are local reactions at the site of injection, which usually do not last more than 1–2 days. 14 x MJ Wiselka. Vaccine safety. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (346 - 357) Generally, the reactions are mild and of a transient nature. It has also been demonstrated that influenza vaccination of patients with asthma is safe. 53 x JM Watson, JF Cordier, KG Nicholson. Does influenza immunisation cause exacerbations of chronic airflow obstruction or asthma?. Thorax 52 (1997) (190 - 194) Crossref. In a large, double-blind, placebo-controlled study, it was demonstrated that no exacerbation of asthma in children occurred as a result of vaccination. 54 x CL Park, AL Frank, M Sullivan, et al.. Influenza vaccination of children during acute asthma exacerbation and concurrent prednisone therapy. Pediatrics 98 (1996) (196 - 200)

It is important to note that there is no vaccination procedure or, for that matter, any medical intervention that bears no risks whatsoever. However, clearly, the benefits of influenza vaccination by far outweigh its risks. Nevertheless, there are widespread misconceptions regarding the risk–benefit ratio of influenza vaccination. Indeed, some vaccinated individuals even complain of having acquired “the flu” as a result of the vaccination. Primary-care physicians and other health-care workers have the responsibility to explain to their patients the favourable risk–benefit ratio of influenza vaccination.

In specific subpopulations, influenza vaccination is contraindicated. These include people with hypersensitivity to eggs and/or a history of immediate allergic reactions following the vaccination. Allergic reactions to flu vaccination are most likely due to the presence of traces of egg-derived components in the vaccine, ovalbumin in particular. Novel developments, specifically the production of influenza vaccine by cell culture technology (see Chapter 9), should eliminate this problem.

There have been reports about a possible association between GBS and influenza vaccination, particularly during the swine flu vaccination campaign in the USA in 1976–77. 55 x TJ Safranek, DN Lawrence, LT Kurland, et al.. Reassessment of the association between Guillain-Barré syndrome and receipt of swine influenza vaccine in 1976–1977: results of a two-state study. Am J Epidemiol 133 (1991) (940 - 951) More recent studies suggest that GBS may occur at a very low rate of about one additional case per million vaccinees. 56 x T Lasky, GJ Terracciano, L Magder, et al.. The Guillain-Barré syndrome and the 1992–1993 and 1993–1994 influenza vaccines. New Engl J Med 339 (1998) (1797 - 1802) Crossref. However, it is unclear whether this marginal increase, against a background incidence of GBS of 10–20 per million, is truly associated with influenza vaccination.

 
x

Figure 28 Relationship between influenza vaccine efficacy and clinical effectiveness of influenza vaccination. The figure shows a hypothetical example in which vaccination is associated with a 35% reduction in all outcomes evaluated (such as hospitalizations for pneumonia). However, not all outcomes are due to influenza. If only 40% of the outcomes represented complications of influenza, the underlying efficacy of the vaccine preventing direct influenza-associated outcomes would be 35%/0.4 = 87.5%. source: Adapted from Nichol KL. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. In: Nicholson KG, Webster RG, Hay AJ, editors. Textbook of Influenza. Blackwell Science, 1998; pp. 358–372 13 x KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) with permission from Blackwell Publishing.

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References in context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
    Go to context

Table 18 Clinical effectiveness of influenza vaccination of the elderly. source: Adapted from Nichol KL. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 2003; 21: 1769–1775 12 x KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Vaccine 21 (2003) (1769 - 1775) Crossref. with permission from Elsevier.

Clinical effectiveness of influenza vaccination of the elderly
Outcome measure Reduction
Community-dwelling senior citizens
Hospitalizations for
 Pneumonia from all causes 33%
 All respiratory conditions 32%
 Congestive heart failure 27%
Death from all causes 50%
Elderly in nursing homes
Respiratory illness 56%
Pneumonia from all causes 53%
Hospitalization in general 48%
Death from all causes 68%

References in context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context

References

Label Authors Title Source Year
9

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  • The safety record of inactivated influenza vaccines is excellent.9,14 Hundreds of millions of vaccine doses are distributed worldwide each year, adverse effects being extremely rare.
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  • These strains are included in the vaccines on recommendation of the WHO.8,9 This recommendation is based on an extensive review of epidemiological data and antigenic and genetic analyses of virus isolates by the four WHO Collaborating Centres.
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  • For a long time, doubts and misconceptions about the risk–benefit ratio of influenza vaccination have hampered the implementation of recommended policies for influenza vaccination.
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  • Inactivated influenza vaccines have an excellent safety record.9,14 Currently, about 300 million vaccine doses are being administered annually around the globe,10 and the overall rate of adverse reactions is extremely low.
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World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 75 (2000) (281 - 288) 2000
10

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  • Vaccination results in reductions of influenza-related respiratory illness and numbers of physician visits among all age groups, and in lower hospitalization rates and deaths among the elderly and patients at risk for serious complications of influenza.12,13 Vaccination coverage among target groups has increased considerably in recent years10 as the awareness of the impact of influenza is growing and influenza has become an important issue on the public-health agenda in many countries.15,16 However, the use of available influenza vaccines is still far from optimal.
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  • However, in recent years, influenza vaccination has become a prominent issue on the public-health agenda in an increasing number of countries.10 Many developed as well as developing countries have now adopted formal recommendations on influenza vaccination for specific target groups.
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  • The elderly represent the primary target group.10,11 This recommendation follows the increased susceptibility of the elderly for infectious diseases in general, which may be explained, at least partly, by a gradual decline in immune competence with age, particularly at the level of T cell function (see Chapter 4).
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  • The elderly represent the primary target group.10,11 This recommendation follows the increased susceptibility of the elderly for infectious diseases in general, which may be explained, at least partly, by a gradual decline in immune competence with age, particularly at the level of T cell function (see Chapter 4).
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  • The elderly represent the primary target group.10,11 This recommendation follows the increased susceptibility of the elderly for infectious diseases in general, which may be explained, at least partly, by a gradual decline in immune competence with age, particularly at the level of T cell function (see Chapter 4).
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  • The most dramatic changes in this respect have occurred in Korea, Latin America, Japan and some central and eastern European countries.10 Figure 27 presents a survey of influenza vaccine distribution in 56 developed and rapidly developing countries in 1997 and 2003.
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  • In 1994, these figures were 80% and 20%, respectively.10 This trend indicates that many countries, including developing countries, are moving towards implementation of measures for influenza prevention and control on an annual basis.
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  • Inactivated influenza vaccines have an excellent safety record.9,14 Currently, about 300 million vaccine doses are being administered annually around the globe,10 and the overall rate of adverse reactions is extremely low.
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  • To improve the vaccination coverage rates in target groups, in accordance with WHO recommendations,10,11,36 it is important that existing national vaccination policies are effectively implemented.
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The Macroepidemiology of Influenza Vaccination (MIV) Study Group. The macroepidemiology of influenza vaccination in 56 countries, 1997–2003. Vaccine 23 (2005) (5133 - 5143) 2005
12

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  • Vaccination results in reductions of influenza-related respiratory illness and numbers of physician visits among all age groups, and in lower hospitalization rates and deaths among the elderly and patients at risk for serious complications of influenza.12,13 Vaccination coverage among target groups has increased considerably in recent years10 as the awareness of the impact of influenza is growing and influenza has become an important issue on the public-health agenda in many countries.15,16 However, the use of available influenza vaccines is still far from optimal.
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  • The recommendation is also based on the proven clinical efficacy and effectiveness of flu vaccination of the elderly.12 In most countries, flu vaccination is recommended for all individuals above 60 or 65 years of age.
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  • The recommendation is also based on the proven clinical efficacy and effectiveness of flu vaccination of the elderly.12 In most countries, flu vaccination is recommended for all individuals above 60 or 65 years of age.
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  • The recommendation is also based on the proven clinical efficacy and effectiveness of flu vaccination of the elderly.12 In most countries, flu vaccination is recommended for all individuals above 60 or 65 years of age.
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  • However, despite the increased vaccine use, recent surveys in Europe show that the coverage rates in target populations are still far from the WHO-recommended 75% in 2010.29,36 The current coverage rates range from 18% (Poland) to 67% (Spain) for the elderly and from 3% to 40% for various risk groups in younger populations.28,29,37 In the USA, only 35% of adults between the ages of 18 and 64 years who are at risk for serious complications due to influenza were being vaccinated in 2003.38 The implication of these findings is that many elderly and at-risk patients are not receiving the best possible protective treatment to prevent influenza or minimize the consequences of an influenza infection.
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  • As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination.12,13,33,35,40 Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below.
    Go to context

  • In evaluating the outcome of influenza vaccination, a distinction is often made between vaccine efficacy per se and the clinical effectiveness of vaccination.12,13 Vaccine efficacy is defined as the reduction in the rate of laboratory-confirmed influenza among vaccinated compared to non-vaccinated individuals.
    Go to context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
    Go to context

  • Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly.12,13,40,48,49 For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population.
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  • Economic evaluations, conducted in many different countries, have indicated that vaccination of senior citizens against influenza is always cost-effective and frequently cost-saving.12,13 For example, in a 6-year study carried out in Minnesota, USA, influenza vaccination of nursing-home residents was associated with an average net saving of $73 per person as a result of reductions in direct medical costs.12 Vaccination appears to be cost-effective or even cost-saving for both healthy senior citizens and high-risk elderly with underlying chronic medical conditions.
    Go to context

  • Economic evaluations, conducted in many different countries, have indicated that vaccination of senior citizens against influenza is always cost-effective and frequently cost-saving.12,13 For example, in a 6-year study carried out in Minnesota, USA, influenza vaccination of nursing-home residents was associated with an average net saving of $73 per person as a result of reductions in direct medical costs.12 Vaccination appears to be cost-effective or even cost-saving for both healthy senior citizens and high-risk elderly with underlying chronic medical conditions.
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  • This is why there is an increasing awareness of the potential benefits of vaccination of working adults.12,13 Several prospective clinical studies have demonstrated the efficacy of inactivated influenza vaccines among healthy younger adults.
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  • As demonstrated by a number of studies, conducted in different countries, vaccination significantly reduces illness, absenteeism and influenza-related costs for healthy adults in the work place.12,13 Indeed, vaccination reduces upper respiratory tract and influenza-like illnesses from all causes by approximately 30%, related physician visits by >40% and work loss by >35% (Table 20).60,61 Accordingly, cost–benefit analyses, based on clinical trials or on modelling, have shown that vaccination of healthy working adults is cost-effective and in many cases cost-saving, provided that indirect costs associated with work absenteeism (see Chapter 6) are explicitly taken into account.62 For example, trials conducted in the USA have shown that – with an average cost for vaccine production and administration of $20 – the net saving would be $23 per person vaccinated.63 In another study comparing 131 vaccinated employees from six textile plants in North Carolina, USA, with 131 age- and gender-matched non-vaccinated controls from different plants, the “cost per saved lost work day” was $22.36, resulting in an overall saving of $2.58 per dollar invested in the vaccination programme.64 Other, model-based, studies also indicate that vaccinating working adults would be cost-saving.12 While recent international guidelines for pharmacoeconomic analyses do explicitly recommend the inclusion of production gains and losses,62 also when such indirect costs are not taken into account, vaccination of adults below the age of 65 turns out to be highly cost-effective.
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  • As demonstrated by a number of studies, conducted in different countries, vaccination significantly reduces illness, absenteeism and influenza-related costs for healthy adults in the work place.12,13 Indeed, vaccination reduces upper respiratory tract and influenza-like illnesses from all causes by approximately 30%, related physician visits by >40% and work loss by >35% (Table 20).60,61 Accordingly, cost–benefit analyses, based on clinical trials or on modelling, have shown that vaccination of healthy working adults is cost-effective and in many cases cost-saving, provided that indirect costs associated with work absenteeism (see Chapter 6) are explicitly taken into account.62 For example, trials conducted in the USA have shown that – with an average cost for vaccine production and administration of $20 – the net saving would be $23 per person vaccinated.63 In another study comparing 131 vaccinated employees from six textile plants in North Carolina, USA, with 131 age- and gender-matched non-vaccinated controls from different plants, the “cost per saved lost work day” was $22.36, resulting in an overall saving of $2.58 per dollar invested in the vaccination programme.64 Other, model-based, studies also indicate that vaccinating working adults would be cost-saving.12 While recent international guidelines for pharmacoeconomic analyses do explicitly recommend the inclusion of production gains and losses,62 also when such indirect costs are not taken into account, vaccination of adults below the age of 65 turns out to be highly cost-effective.
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  • Finally, vaccination of children appears to be highly cost-effective and in many cases cost-saving.
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KL Nichol. The efficacy, effectiveness and cost-effectiveness of inactivated influenza virus vaccines. Crossref. Vaccine 21 (2003) (1769 - 1775) 2003
13

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  • Vaccination results in reductions of influenza-related respiratory illness and numbers of physician visits among all age groups, and in lower hospitalization rates and deaths among the elderly and patients at risk for serious complications of influenza.12,13 Vaccination coverage among target groups has increased considerably in recent years10 as the awareness of the impact of influenza is growing and influenza has become an important issue on the public-health agenda in many countries.15,16 However, the use of available influenza vaccines is still far from optimal.
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  • Table 17 presents the recommendations for influenza vaccination adopted in most countries.
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  • As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination.12,13,33,35,40 Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below.
    Go to context

  • In evaluating the outcome of influenza vaccination, a distinction is often made between vaccine efficacy per se and the clinical effectiveness of vaccination.12,13 Vaccine efficacy is defined as the reduction in the rate of laboratory-confirmed influenza among vaccinated compared to non-vaccinated individuals.
    Go to context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
    Go to context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
    Go to context

  • Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly.12,13,40,48,49 For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population.
    Go to context

  • Economic evaluations, conducted in many different countries, have indicated that vaccination of senior citizens against influenza is always cost-effective and frequently cost-saving.12,13 For example, in a 6-year study carried out in Minnesota, USA, influenza vaccination of nursing-home residents was associated with an average net saving of $73 per person as a result of reductions in direct medical costs.12 Vaccination appears to be cost-effective or even cost-saving for both healthy senior citizens and high-risk elderly with underlying chronic medical conditions.
    Go to context


  • Go to context

  • This is why there is an increasing awareness of the potential benefits of vaccination of working adults.12,13 Several prospective clinical studies have demonstrated the efficacy of inactivated influenza vaccines among healthy younger adults.
    Go to context

  • As demonstrated by a number of studies, conducted in different countries, vaccination significantly reduces illness, absenteeism and influenza-related costs for healthy adults in the work place.12,13 Indeed, vaccination reduces upper respiratory tract and influenza-like illnesses from all causes by approximately 30%, related physician visits by >40% and work loss by >35% (Table 20).60,61 Accordingly, cost–benefit analyses, based on clinical trials or on modelling, have shown that vaccination of healthy working adults is cost-effective and in many cases cost-saving, provided that indirect costs associated with work absenteeism (see Chapter 6) are explicitly taken into account.62 For example, trials conducted in the USA have shown that – with an average cost for vaccine production and administration of $20 – the net saving would be $23 per person vaccinated.63 In another study comparing 131 vaccinated employees from six textile plants in North Carolina, USA, with 131 age- and gender-matched non-vaccinated controls from different plants, the “cost per saved lost work day” was $22.36, resulting in an overall saving of $2.58 per dollar invested in the vaccination programme.64 Other, model-based, studies also indicate that vaccinating working adults would be cost-saving.12 While recent international guidelines for pharmacoeconomic analyses do explicitly recommend the inclusion of production gains and losses,62 also when such indirect costs are not taken into account, vaccination of adults below the age of 65 turns out to be highly cost-effective.
    Go to context

KL Nichol. Efficacy/clinical effectiveness of inactivated influenza virus vaccines in adults. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (358 - 372) 1998
14

References in context

  • The safety record of inactivated influenza vaccines is excellent.9,14 Hundreds of millions of vaccine doses are distributed worldwide each year, adverse effects being extremely rare.
    Go to context

  • The most frequently occurring side effects are local reactions at the site of injection, which usually do not last more than 1–2 days.14 Generally, the reactions are mild and of a transient nature.
    Go to context

  • The most frequently occurring side effects are local reactions at the site of injection, which usually do not last more than 1–2 days.14 Generally, the reactions are mild and of a transient nature.
    Go to context

MJ Wiselka. Vaccine safety. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (346 - 357) 1998
33

References in context

  • Table 17 presents the recommendations for influenza vaccination adopted in most countries.
    Go to context

  • As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination.12,13,33,35,40 Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below.
    Go to context


  • Go to context

  • However, there is increasing epidemiological evidence of the burden of disease in children33 and of vaccination effectiveness.33,35,66 In addition to the direct benefits for the vaccinated children, a vaccination programme for children may also have the potential for reducing the impact of influenza epidemics, because children play an important role in the spread of influenza infections in communities.66,67 In addition, influenza among children is a significant cause of parental work loss.
    Go to context

  • However, there is increasing epidemiological evidence of the burden of disease in children33 and of vaccination effectiveness.33,35,66 In addition to the direct benefits for the vaccinated children, a vaccination programme for children may also have the potential for reducing the impact of influenza epidemics, because children play an important role in the spread of influenza infections in communities.66,67 In addition, influenza among children is a significant cause of parental work loss.
    Go to context

  • However, there is increasing epidemiological evidence of the burden of disease in children33 and of vaccination effectiveness.33,35,66 In addition to the direct benefits for the vaccinated children, a vaccination programme for children may also have the potential for reducing the impact of influenza epidemics, because children play an important role in the spread of influenza infections in communities.66,67 In addition, influenza among children is a significant cause of parental work loss.
    Go to context

T Heikkinen, R Booy, M Campins, et al.. Should healthy children be vaccinated against influenza? A consensus report of the Summits of Independent European Vaccination Experts. Eur J Pediatr 21 (2005) (1 - 6) 2005
34

References in context

  • Table 17 presents the recommendations for influenza vaccination adopted in most countries.
    Go to context

  • Because of the non-specific criteria of influenza-like illness (ILI), the outcome of clinical effectiveness studies depends on the used case definition in the particular study.
    Go to context

T Heikkinen, O Ruuskanen. Influenza vaccines in healthy children (letter to the editor). Crossref. Lancet 365 (2005) (2086 - 2087) 2005
35

References in context

  • Table 17 presents the recommendations for influenza vaccination adopted in most countries.
    Go to context

  • As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination.12,13,33,35,40 Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below.
    Go to context

  • However, there is increasing epidemiological evidence of the burden of disease in children33 and of vaccination effectiveness.33,35,66 In addition to the direct benefits for the vaccinated children, a vaccination programme for children may also have the potential for reducing the impact of influenza epidemics, because children play an important role in the spread of influenza infections in communities.66,67 In addition, influenza among children is a significant cause of parental work loss.
    Go to context

  • A similar observation has been made in a recent study in Russia.35 School children in some regions in the Moscow area were systematically vaccinated with a classical inactivated subunit vaccine, whereas in control areas no such vaccination strategy was installed.
    Go to context

  • A similar observation has been made in a recent study in Russia.35 School children in some regions in the Moscow area were systematically vaccinated with a classical inactivated subunit vaccine, whereas in control areas no such vaccination strategy was installed.
    Go to context

YZ Ghendon, AN Kaira, GA Elshina. The effect of mass influenza immunization in children on the morbidity of the unvaccinated elderly. Epidemiol Infect 134 (2006) (71 - 78) 2006
37

References in context

  • However, despite the increased vaccine use, recent surveys in Europe show that the coverage rates in target populations are still far from the WHO-recommended 75% in 2010.29,36 The current coverage rates range from 18% (Poland) to 67% (Spain) for the elderly and from 3% to 40% for various risk groups in younger populations.28,29,37 In the USA, only 35% of adults between the ages of 18 and 64 years who are at risk for serious complications due to influenza were being vaccinated in 2003.38 The implication of these findings is that many elderly and at-risk patients are not receiving the best possible protective treatment to prevent influenza or minimize the consequences of an influenza infection.
    Go to context

  • The value of immunization against influenza is sometimes being questioned, as outbreaks of flu continue despite increased influenza vaccination coverage.39 Therefore, there has been a strong demand for sound scientific data on the effects of influenza vaccination.
    Go to context

SA Smith, GA Poland. The use of influenza and pneumococcal vaccines in people with diabetes (technical review). Crossref. Diabetes Care 23 (2000) (95 - 108) 2000
39

References in context

  • The value of immunization against influenza is sometimes being questioned, as outbreaks of flu continue despite increased influenza vaccination coverage.39 Therefore, there has been a strong demand for sound scientific data on the effects of influenza vaccination.
    Go to context

DS Fedson, K Nichol. Should we question the benefits of influenza vaccination for elderly people? Infectious Disease News, Guest Editorial. (www.infectiousdiseasenews.com/200508/guested1.asp) (August 2005) August 2005
40

References in context

  • As a result, many clinical studies have now produced consistent data showing the clear-cut benefits of influenza vaccination.12,13,33,35,40 Since the elderly comprise by far the largest target population for flu vaccination, the majority of studies evaluating the benefits of vaccination have been conducted among people in this age group; these will be discussed in more detail below.
    Go to context

  • It is defined as the reduction of clinically relevant, but not necessarily influenza-specific, disease in a “real-life” situation, including all influenza-like illness (ILI), hospitalizations due to pneumonia from all causes or death from all causes.12,13,40 As this parameter includes – by definition – disease that is not caused by the influenza virus, clinical effectiveness of vaccination is generally estimated to be lower than the actual vaccine efficacy, as illustrated by the hypothetical example presented in Figure 28.13 Therefore, clinical effectiveness should not be confused for vaccine efficacy, as this may result in a substantial underestimation of the actual performance of the vaccine.
    Go to context

  • Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly.12,13,40,48,49 For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population.
    Go to context


  • Go to context

AC Voordouw, MC Sturkenboom, JP Dieleman, et al.. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. Crossref. J Am Med Assoc 292 (2004) (2089 - 2095) 2004
41

References in context

  • The value of immunization against influenza is sometimes being questioned, as outbreaks of flu continue despite increased influenza vaccination coverage.39 Therefore, there has been a strong demand for sound scientific data on the effects of influenza vaccination.
    Go to context

  • In most countries, healthy toddlers and children are not included in the target groups for annual influenza immunization.
    Go to context

  • The efficacy of influenza vaccination among children has been evaluated in a number of randomized, controlled trials, involving the use of either trivalent inactivated or experimental live-attenuated vaccines.68–70 From these studies, it appears that vaccination is highly efficacious in terms of preventing laboratory-confirmed influenza for children in their teens (∼90%), whereas a lower efficacy is seen with younger children (Table 20).
    Go to context

SA Harper, K Fukuda, TM Uyeki, et al.. Advisory Committee on Immunization Practices (ACIP), Centers for Disease Control and Prevention (CDC). Prevention and control of influenza. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 54 (RR-8) (2005) (1 - 40) 2005
42

References in context

  • The value of immunization against influenza is sometimes being questioned, as outbreaks of flu continue despite increased influenza vaccination coverage.39 Therefore, there has been a strong demand for sound scientific data on the effects of influenza vaccination.
    Go to context

  • The vaccination was associated with significant reductions in pneumonia (29–32%), cardiac disease (19%) and cerebrovascular disease (16–23%).42 Other studies have indicated that influenza vaccination of patients who have had a myocardial infarction results in a significant reduction in 1-year mortality rates (66% reduction) or risk of further ischaemic events.
    Go to context

KL Nichol, J Nordin, J Mullooly, et al.. Influenza vaccination and reduction in hospitalizations for cardiac disease and stroke among the elderly. Crossref. New Engl J Med 348 (2003) (1322 - 1332) 2003
43

References in context

  • Indeed, applying different case definitions to one data set from a single clinical study resulted in very different study outcomes.43 A recent literature review revealed that all published clinical effectiveness studies applied different case definitions for ILI44 and that by simply changing the sensitivity and specificity of case definitions and observation periods, differences of as much as 30% in study outcome for vaccination effectiveness may be found.
    Go to context

KL Nichol, P Mendelman. Influence of clinical case definitions with differing levels of sensitivity and specificity on estimates of the relative and absolute health benefits of influenza vaccination among healthy working adults and implications for economic analyses. Crossref. Virus Res 103 (2004) (3 - 8) 2004
44

References in context

  • Indeed, applying different case definitions to one data set from a single clinical study resulted in very different study outcomes.43 A recent literature review revealed that all published clinical effectiveness studies applied different case definitions for ILI44 and that by simply changing the sensitivity and specificity of case definitions and observation periods, differences of as much as 30% in study outcome for vaccination effectiveness may be found.
    Go to context

  • Indeed, applying different case definitions to one data set from a single clinical study resulted in very different study outcomes.43 A recent literature review revealed that all published clinical effectiveness studies applied different case definitions for ILI44 and that by simply changing the sensitivity and specificity of case definitions and observation periods, differences of as much as 30% in study outcome for vaccination effectiveness may be found.
    Go to context

WEP Beyer. Heterogeneity of case-definitions used in vaccine effectiveness studies and its impact on meta-analysis. Vaccine (2006) in press. 2006
45

References in context

  • In recent systematic reviews (Cochrane) on influenza vaccination effectiveness in healthy adults45 and children,46 literature data were pooled for the review process, but the differences in case definitions of individual studies were not taken into account.
    Go to context

V Demicheli, D Rivetti, JJ Deeks, et al.. Vaccines for preventing influenza in healthy adults. Cochrane Database Syst Rev 3 (2004) CD001269 Review. 2004
46

References in context

  • In recent systematic reviews (Cochrane) on influenza vaccination effectiveness in healthy adults45 and children,46 literature data were pooled for the review process, but the differences in case definitions of individual studies were not taken into account.
    Go to context

T Jefferson, S Smith, V Demicheli, et al.. Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet 365 (2005) (773 - 780) 2005
47

References in context

  • Because of the non-specific criteria of influenza-like illness (ILI), the outcome of clinical effectiveness studies depends on the used case definition in the particular study.
    Go to context

K Nichol, J Nordin, J Mullooly. Influence of clinical outcome and outcome period definitions on estimates of absolute clinical and economic benefits of influenza vaccination in community dwelling elderly persons. Crossref. Vaccine 24 (2006) (1562 - 1568) 2006
48

References in context

  • For example, in a large, randomized, double-blind, placebo-controlled trial among 1838 subjects of 60 years of age or older in the Netherlands, vaccine efficacy was found to be 58%.48 This trial was conducted in the 1991–92 winter season and involved the use of a multivalent inactivated influenza vaccine, matching well with the circulating virus.
    Go to context

  • Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly.12,13,40,48,49 For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population.
    Go to context


  • Go to context

TME Govaert, CTMCN Thijs, N Masurel, et al.. The efficacy of influenza vaccination in elderly individuals. A randomized double-blind placebo-controlled trial. J Am Med Assoc 272 (1994) (1661 - 1665) 1994
49

References in context

  • Numerous studies have convincingly demonstrated the clinical benefits of influenza vaccination in the elderly.12,13,40,48,49 For example, in a large study in the USA, spanning two influenza seasons (1998–2000) and involving 300,000 community-dwelling elderly people (≥65 years), influenza vaccination was performed in 55.5–59.7% of the population.
    Go to context


  • Go to context

KL Nichol. Influenza vaccination in the elderly. Impact on hospitalization and mortality. Crossref. Drugs Aging 22 (2005) (495 - 515) 2005
50

References in context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context


  • Go to context

T Vu, S Farish, M Jenkins, H Kelly. A meta-analysis of effectiveness of influenza vaccine in persons aged 65 years and over living in the community. Crossref. Vaccine 20 (2002) (1831 - 1836) 2002
51

References in context

  • A meta-analysis, including a large number of individual studies among senior citizens living in the community, concluded that vaccination significantly reduces hospitalization and death rates among the elderly (Table 18).50 Another meta-analysis has shown that influenza vaccination is also highly effective among residents of nursing homes (Table 18).51 These findings necessitate a proactive immunization practice by health-care providers in order to allow more elderly people to benefit from existing safe and efficacious influenza vaccines.
    Go to context


  • Go to context

PA Gross, AW Hermogenes, HS Sachs, J Lau, RA Levandowski. The efficacy of influenza vaccine in elderly persons: a meta-analysis and review of the literature. Ann Intern Med 123 (1995) (518 - 527) 1995
52

References in context

  • In a study conducted in the Netherlands in the 1995–96 and 1997–98 seasons, influenza vaccination was found to be cost-saving for high-risk elderly and cost-effective for all elderly and elderly at low risk, the cost-effectiveness ratios being &z.euro;1820 per life-year gained for all elderly and &z.euro;6900 per life-year gained for those at low risk.52 Similar studies have been conducted in other countries with similar outcomes.
    Go to context

MJ Postma, JM Bos, M Van Gennip, et al.. Economic evaluation of influenza vaccination. Assessment for The Netherlands. Crossref. Pharmacoeconomics 16 (Suppl 1) (1999) (33 - 40) 1999
53

References in context

  • Inactivated influenza vaccines have an excellent safety record.9,14 Currently, about 300 million vaccine doses are being administered annually around the globe,10 and the overall rate of adverse reactions is extremely low.
    Go to context

JM Watson, JF Cordier, KG Nicholson. Does influenza immunisation cause exacerbations of chronic airflow obstruction or asthma?. Crossref. Thorax 52 (1997) (190 - 194) 1997
54

References in context

  • Inactivated influenza vaccines have an excellent safety record.9,14 Currently, about 300 million vaccine doses are being administered annually around the globe,10 and the overall rate of adverse reactions is extremely low.
    Go to context

CL Park, AL Frank, M Sullivan, et al.. Influenza vaccination of children during acute asthma exacerbation and concurrent prednisone therapy. Pediatrics 98 (1996) (196 - 200) 1996
55

References in context

  • There have been reports about a possible association between GBS and influenza vaccination, particularly during the swine flu vaccination campaign in the USA in 1976–77.55 More recent studies suggest that GBS may occur at a very low rate of about one additional case per million vaccinees.56 However, it is unclear whether this marginal increase, against a background incidence of GBS of 10–20 per million, is truly associated with influenza vaccination.
    Go to context

TJ Safranek, DN Lawrence, LT Kurland, et al.. Reassessment of the association between Guillain-Barré syndrome and receipt of swine influenza vaccine in 1976–1977: results of a two-state study. Am J Epidemiol 133 (1991) (940 - 951) 1991
56

References in context

  • There have been reports about a possible association between GBS and influenza vaccination, particularly during the swine flu vaccination campaign in the USA in 1976–77.55 More recent studies suggest that GBS may occur at a very low rate of about one additional case per million vaccinees.56 However, it is unclear whether this marginal increase, against a background incidence of GBS of 10–20 per million, is truly associated with influenza vaccination.
    Go to context

T Lasky, GJ Terracciano, L Magder, et al.. The Guillain-Barré syndrome and the 1992–1993 and 1993–1994 influenza vaccines. Crossref. New Engl J Med 339 (1998) (1797 - 1802) 1998

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