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ECDC INTERIM GUIDANCE - Use of specific pandemic influenza vaccines during the H1N1 2009 pandemic - August 2009 (ECDC, excerpts, edited)

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  • ECDC INTERIM GUIDANCE - Use of specific pandemic influenza vaccines during the H1N1 2009 pandemic - August 2009 (ECDC, excerpts, edited)

    ECDC INTERIM GUIDANCE - Use of specific pandemic influenza vaccines during the H1N1 2009 pandemic - August 2009 (ECDC, excerpts, edited)

    [Original Full Document: LINK. EDITED.]

    ECDC INTERIM GUIDANCE - Use of specific pandemic influenza vaccines during the H1N1 2009 pandemic - August 2009


    Executive summary

    In April 2009, a new strain of human influenza A(H1N1) was identified and characterised. The attack rates for this A(H1N1) pandemic strain are expected to be higher than for seasonal strains because of the lower levels of preexisting immunity in the population (except for older people, many of whom do seem to have a degree of immunity). Therefore the actual numbers of cases of influenza presenting to health services in a short period of time is likely to be higher than those of seasonal influenza.

    Vaccination with a strain-specific pandemic vaccine is considered one of the most effective countermeasures for protecting individuals in the event of a pandemic. However, specific pandemic vaccines will not become available all at once, delivery from the manufacturers will necessarily be staggered, and there will also be difficulties in distribution. Ensuring vaccine supply will be difficult within a reasonable timeframe. Strategic use of vaccines, after careful prioritisation between different population groups, will be important to maximise the benefit of the available doses.

    Overall objectives of vaccination should be specified before deciding who should be offered the vaccine and how to prioritise target populations. These may legitimately differ by country and/or region. They will particularly differ according to the resources, amounts of vaccine, numbers of syringes, etc. that are available and practical issues relating to distribution and delivery. These differences between countries will pose communication problems when they become apparent and these should be prepared for.

    The objectives of a pandemic vaccination strategy can be considered in two broad categories which are by no means mutually exclusive: a) mitigation, to protect the individuals that may be at greatest risk of severe disease; and b) protecting essential services.

    Influenza A(H1N1)v is a novel virus and pandemics in modern times have all differed one from another and from the current seasonal influenza. Hence, risk groups (those at higher risk of severe disease) may differ from those for seasonal influenza strains.

    Also, different strategies come into play with greater emphasis on the need to maintain essential services by immunisation. Hence target groups (groups that are offered vaccine who may or may not be in the risk groups) may also be different.

    According to the current evidence on the A(H1N1) 2009 pandemic, the following population groups can be identified as risk groups:

    • people aged less than 65 years with chronic underlying conditions, namely:
      • chronic respiratory diseases;
      • chronic cardiovascular diseases;
      • chronic metabolic disorders (notably diabetes);
      • chronic renal and hepatic diseases;
      • persons with deficient immunity (congenital or acquired);
      • chronic neurological or neuromuscular conditions;
      • any other condition that impairs a person?s immunity or prejudices their respiratory function;
    • young children (especially under the age of two years);
    • pregnant women.


    This list differs somewhat from the groups for whom many countries recommend seasonal influenza immunisation, especially with regard to people aged 65 years and over. Older people seem generally to be at lower risk of infection ? possibly due to existing immunity ? but there are indications that if they do become infected they suffer more severe disease than younger adults.

    In addition, there are other groups to whom immunisation may be offered even though they are not at higher risk of severe disease (target groups). There are arguments for offering vaccination to children since they are experiencing high attack rates (albeit of mild disease) and may be particularly important in amplifying local outbreaks. There are also arguments for offering immunisation to all healthcare workers. This is both to prevent people in risk groups becoming infected from healthcare workers and to protect the healthcare worker from infected patients, thereby sustaining healthcare services. There are advantages to offering immunisation to people who care for those for whom immunisation may not be effective (e.g. people under treatment with immunosuppressive therapy). Babies under six months of age cannot at this stage be immunised because of lack of data on immunogenicity and safety and there are therefore arguments for offering vaccination to those that are in closest contact with them.

    Other potential target groups are workers essential for the response to the pandemic.

    This guidance is based on the current scenario of the A(H1N1) 2009 pandemic. Particular areas of uncertainty are noted and discussed. As more data, evidence and opinions become available this document will be updated along with the ECDC risk assessment to which it is linked [1].

    Based on the experience from previous pandemics, during which the pathogenicity and transmissibility of the virus increased over time, three other scenarios are presented. There are also annexes summarising the evidence for vaccination of particular risk groups for seasonal influenza and the current pandemic influenza and giving broad estimates of the size of the risk and target groups. The basis for the calculation is given in sufficient detail that people in the Member States can apply the methodology to their own population or compare the methods already used.

    Comments on this interim guidance are welcomed and encouraged and should be sent to PHE.H1N1v@ecdc.europa.eu

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