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Vaccination: Cornerstone of Influenza Control

Vaccination is the primary and single most cost-effective method of preventing influenza. Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933. 1, x W Smith, CH Andrews, PP Laidlaw. A virus obtained from influenza patients. Lancet ii (1933) (66 - 68) Crossref. 2 x JM Wood, MS Williams. History of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (317 - 323) Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies. 2, x JM Wood, MS Williams. History of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (317 - 323) 3 x T Francis, TP Magill. The incidence of neutralizing antibodies for human influenza virus in the serum of human individuals of different ages. J Exp Med 63 (1936) (655 - 668) Crossref. Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s. 2 x JM Wood, MS Williams. History of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (317 - 323) Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA). 2, x JM Wood, MS Williams. History of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (317 - 323) 4, x IGS Furminger. Vaccine production. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (324 - 332) 5 x JM Wood. Standardization of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (333 - 345) These vaccines are generally produced from virus grown on embryonated chicken eggs.

Active immunization against any infectious disease, including influenza, aims at induction of antimicrobial immunity by inoculating the person with an attenuated or inactivated form of the pathogen involved. Following such an approach, one attempts to closely mimic the immune response to a natural infection, which is often considered the “gold standard” for protection. Thus far, the hallmark for influenza vaccine efficacy has been the induction of an adequate level of virus-neutralizing antibodies in the serum.5, 6, and 7 x JM Wood. Standardization of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (333 - 345) x D Hobson, RL Curry, AS Beare, A Ward-Gardner. The role of serum haemagglutination-inhibiting antibody in protection against challenge virus infection with A2 and B viruses. J Hyg (Lond) 70 (1972) (767 - 777) Crossref. x PR Small, RA Waldman, JC Bruono, GE Gifford. Influenza infection in ferrets: Role of serum antibody in protection and recovery. Infect Immun 13 (1976) (417 - 424) These antibodies are primarily directed against the envelope glycoproteins of the virus, HA and NA, HA being the major target for virus-neutralizing antibodies (see Chapter 4). It is well established that HA-specific antibodies in the circulation protect from severe viral pneumonia as a result of transudation of these antibodies from the blood into the lungs. 6, x D Hobson, RL Curry, AS Beare, A Ward-Gardner. The role of serum haemagglutination-inhibiting antibody in protection against challenge virus infection with A2 and B viruses. J Hyg (Lond) 70 (1972) (767 - 777) Crossref. 7 x PR Small, RA Waldman, JC Bruono, GE Gifford. Influenza infection in ferrets: Role of serum antibody in protection and recovery. Infect Immun 13 (1976) (417 - 424)

Current influenza vaccines contain antigens from two influenza A virus strains and one B strain, according to annual recommendation by the WHO. 8, x Y Ghendon. Influenza surveillance. Bull World Health Org 61 (1991) (509 - 515) 9 x World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 75 (2000) (281 - 288) To ensure an optimal antigenic match between the virus strains in the vaccine and the viruses circulating in the subsequent influenza season, this WHO recommendation is based on intensive surveillance of new influenza strains around the globe, allowing an informed selection of strains to be included in the next annual vaccine. 8, x Y Ghendon. Influenza surveillance. Bull World Health Org 61 (1991) (509 - 515) 9 x World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 75 (2000) (281 - 288)

Today, many countries have implemented influenza vaccination programmes, the primary target groups for vaccination including the elderly and people with underlying medical conditions which make them vulnerable to serious complications of influenza.9, 10, and 11 x World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 75 (2000) (281 - 288) x The Macroepidemiology of Influenza Vaccination (MIV) Study Group. The macroepidemiology of influenza vaccination in 56 countries, 1997–2003. Vaccine 23 (2005) (5133 - 5143) x World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 77 (2002) (230 - 239) Also, there is increasing awareness of the potential societal and health benefits of vaccinating working adults and children. 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)

The safety record of inactivated influenza vaccines is excellent. 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) Hundreds of millions of vaccine doses are distributed worldwide each year, adverse effects being extremely rare. Influenza vaccination has been shown to be highly effective. 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, 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) Vaccination coverage among target groups has increased considerably in recent years 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) 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, x K Stöhr. The global agenda on influenza surveillance and control. Vaccine 21 (2003) (1744 - 1748) 16 x World Health Organization. Global agenda on influenza – adopted version. Part I. Wkly Epidemiol Rec 77 (2002) (179 - 182) Part II, Wkly Epidemiol Rec 77 (2002) (191 - 196) (www.who.int/emc/diseases/flu/global_agenda_report/Contentpandemic.htm) However, the use of available influenza vaccines is still far from optimal. Health-care professionals are in a key position to explain the favourable risk–benefit ratio of influenza vaccination to people in target groups and thus to motivate them to take the vaccine. Indeed, increased use of influenza vaccines is expected to significantly reduce epidemics and to improve our preparedness for potential new pandemic outbreaks.

Key Messages

  • Current inactivated influenza vaccines have an excellent safety record.
  • Influenza vaccination results in significant reductions in influenza-related respiratory illness, hospitalization rates and deaths among the elderly and patients at risk for serious complications of influenza.
  • Influenza vaccination of the elderly and patients with underlying medical conditions is cost-effective and in many cases cost-saving.
  • Scientific evidence also demonstrates the benefits of vaccinating healthy working adults and children.
  • Misconceptions about the benefits of influenza vaccination and overestimation of its risks lead to decreased acceptance and suboptimal use of influenza vaccines.
  • Primary-care physicians and other health-care workers play a pivotal role in explaining the favourable risk–benefit ratio of influenza vaccination and in motivating patients in target groups to take the vaccinaton.
  • The WHO strongly encourages the use of influenza vaccine among the elderly and people in other target groups.

References

Label Authors Title Source Year
1

References in context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

W Smith, CH Andrews, PP Laidlaw. A virus obtained from influenza patients. Crossref. Lancet ii (1933) (66 - 68) 1933
2

References in context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • However, despite the introduction of improved techniques for virus purification, local reactogenicity and systemic side effects remain a problem associated with the use of these vaccines, particularly in small children.17 This has led to the development of vaccine formulations consisting of disrupted virus particles, which turned out to be almost equally immunogenic in primed individuals, yet causing significantly fewer side effects.2 These split-virus vaccines, first licensed in the USA in 1968, are among the most widely used formulations to date.
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  • However, despite the introduction of improved techniques for virus purification, local reactogenicity and systemic side effects remain a problem associated with the use of these vaccines, particularly in small children.17 This has led to the development of vaccine formulations consisting of disrupted virus particles, which turned out to be almost equally immunogenic in primed individuals, yet causing significantly fewer side effects.2 These split-virus vaccines, first licensed in the USA in 1968, are among the most widely used formulations to date.
    Go to context

JM Wood, MS Williams. History of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (317 - 323) 1998
3

References in context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

T Francis, TP Magill. The incidence of neutralizing antibodies for human influenza virus in the serum of human individuals of different ages. Crossref. J Exp Med 63 (1936) (655 - 668) 1936
4

References in context

  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • Initial inactivated influenza vaccine formulations invariably consisted of whole inactivated virus formulations.2,4 Whole inactivated virus vaccines are generally quite immunogenic.
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  • Initial inactivated influenza vaccine formulations invariably consisted of whole inactivated virus formulations.2,4 Whole inactivated virus vaccines are generally quite immunogenic.
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  • Removal of the detergent from the supernatant by adsorption onto a hydrophobic resin, such as Amberlite, results in the formation of rosettes of HA and NA, with only small amounts of contaminating core proteins, such as NP or M1, and viral membrane lipid.4 Influenza subunit vaccines were first licensed in UK in 1980 and are now used in many countries worldwide.
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  • Removal of the detergent from the supernatant by adsorption onto a hydrophobic resin, such as Amberlite, results in the formation of rosettes of HA and NA, with only small amounts of contaminating core proteins, such as NP or M1, and viral membrane lipid.4 Influenza subunit vaccines were first licensed in UK in 1980 and are now used in many countries worldwide.
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IGS Furminger. Vaccine production. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (324 - 332) 1998
5

References in context

  • Single radial immunodiffusion (SRD) test of influenza vaccine potency.5 Serial dilutions of detergent-treated vaccine, and a reference antigen (Ref), are added to wells in an agarose gel containing a sheep antiserum against the relevant HA.
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  • Flu vaccine development began just a few years after the first isolation of the influenza virus in 1933.1,2 Pioneering studies demonstrated that influenza A/PR/8/34 (H1N1) virus would infect humans upon subcutaneous administration, inducing virus-neutralizing antibodies.2,3 Soon after these initial observations, studies using formalin-inactivated whole-virus preparations were conducted, the first inactivated influenza vaccines being introduced in the 1940s.2 Most current influenza vaccines are also inactivated formulations, consisting of either split virus or subunit preparations, the latter containing just the isolated viral haemagglutinin (HA) and neuraminidase (NA).2,4,5 These vaccines are generally produced from virus grown on embryonated chicken eggs.
    Go to context

  • Thus far, the hallmark for influenza vaccine efficacy has been the induction of an adequate level of virus-neutralizing antibodies in the serum.5–7 These antibodies are primarily directed against the envelope glycoproteins of the virus, HA and NA, HA being the major target for virus-neutralizing antibodies (see Chapter 4).
    Go to context

  • That this system of surveillance and recommendation works quite well is demonstrated by the good match achieved in, for example, the influenza seasons from 1987 to 1997.5 Within this period, 23 vaccine strains recommended by the WHO matched with the subsequently circulating total of 30 virus strains (Table 15).
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  • This dose scheme has been formally standardized.5,23,24 The trivalent inactivated influenza vaccine is administered by intramuscular or deep subcutaneous injection.
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  • Not only has the composition of influenza vaccines been standardized in many countries, in the EU, criteria for vaccine immunogenicity have also been implemented.5,22,23 As indicated above, current inactivated influenza vaccines aim at induction of an efficient systemic antibody response against the viral surface antigens.
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  • Antibody titres are generally determined on the basis of haemagglutination–inhibition (HI) activity5,6 or, occasionally, by single radial haemolysis (SRH).5 In the HI assay, serum samples of vaccinated individuals are tested for their ability to inhibit agglutination of erythrocytes, induced by influenza virus through interaction of the viral HA with sialic acid on the red cell surface.
    Go to context

  • Antibody titres are generally determined on the basis of haemagglutination–inhibition (HI) activity5,6 or, occasionally, by single radial haemolysis (SRH).5 In the HI assay, serum samples of vaccinated individuals are tested for their ability to inhibit agglutination of erythrocytes, induced by influenza virus through interaction of the viral HA with sialic acid on the red cell surface.
    Go to context

  • Antibody titres are generally determined on the basis of haemagglutination–inhibition (HI) activity5,6 or, occasionally, by single radial haemolysis (SRH).5 In the HI assay, serum samples of vaccinated individuals are tested for their ability to inhibit agglutination of erythrocytes, induced by influenza virus through interaction of the viral HA with sialic acid on the red cell surface.
    Go to context

JM Wood. Standardization of inactivated influenza vaccines. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (333 - 345) 1998
6

References in context

  • Thus far, the hallmark for influenza vaccine efficacy has been the induction of an adequate level of virus-neutralizing antibodies in the serum.5–7 These antibodies are primarily directed against the envelope glycoproteins of the virus, HA and NA, HA being the major target for virus-neutralizing antibodies (see Chapter 4).
    Go to context

  • Active immunization against any infectious disease, including influenza, aims at induction of antimicrobial immunity by inoculating the person with an attenuated or inactivated form of the pathogen involved.
    Go to context

  • Antibody titres are generally determined on the basis of haemagglutination–inhibition (HI) activity5,6 or, occasionally, by single radial haemolysis (SRH).5 In the HI assay, serum samples of vaccinated individuals are tested for their ability to inhibit agglutination of erythrocytes, induced by influenza virus through interaction of the viral HA with sialic acid on the red cell surface.
    Go to context

D Hobson, RL Curry, AS Beare, A Ward-Gardner. The role of serum haemagglutination-inhibiting antibody in protection against challenge virus infection with A2 and B viruses. Crossref. J Hyg (Lond) 70 (1972) (767 - 777) 1972
7

References in context

  • Thus far, the hallmark for influenza vaccine efficacy has been the induction of an adequate level of virus-neutralizing antibodies in the serum.5–7 These antibodies are primarily directed against the envelope glycoproteins of the virus, HA and NA, HA being the major target for virus-neutralizing antibodies (see Chapter 4).
    Go to context

  • Active immunization against any infectious disease, including influenza, aims at induction of antimicrobial immunity by inoculating the person with an attenuated or inactivated form of the pathogen involved.
    Go to context

PR Small, RA Waldman, JC Bruono, GE Gifford. Influenza infection in ferrets: Role of serum antibody in protection and recovery. Infect Immun 13 (1976) (417 - 424) 1976
8

References in context


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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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Y Ghendon. Influenza surveillance. Bull World Health Org 61 (1991) (509 - 515) 1991
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

References in context


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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.
    Go to context

  • 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
11

References in context


  • Go to context

  • 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).
    Go to context


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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.
    Go to context

World Health Organization. Influenza vaccines. Wkly Epidemiol Rec 77 (2002) (230 - 239) 2002
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.
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  • 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.
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  • 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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  • 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.
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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.
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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.
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  • 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.
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  • 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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  • 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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  • 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.
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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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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

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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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  • 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.
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  • 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.
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MJ Wiselka. Vaccine safety. KG Nicholson, RG Webster, AJ Hay (Eds.) Textbook of Influenza (Blackwell Science, 1998) (346 - 357) 1998
15

References in context

  • 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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K Stöhr. The global agenda on influenza surveillance and control. Vaccine 21 (2003) (1744 - 1748) 2003
16

References in context

  • 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.
    Go to context

World Health Organization. Global agenda on influenza – adopted version. Part I. Wkly Epidemiol Rec 77 (2002) (179 - 182) Part II, Wkly Epidemiol Rec 77 (2002) (191 - 196) (www.who.int/emc/diseases/flu/global_agenda_report/Contentpandemic.htm) 2002

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