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WHO Global Influenza Surveillance Network (GISN)
Surveillance and Vaccine Development

The WHO Global Influenza Surveillance Network (GISN) monitors which influenza viruses are circulating in humans around the world throughout the year. GISN comprises:

  •   5 WHO Collaborating Centres (Atlanta, Beijing, London, Melbourne, Tokyo)
  •   136 National Influenza Centres in 106 countries
  •   11 H5 Reference Laboratories
  •   4 Essential Regulatory Laboratories

The major technical roles of GISN are to:

  •  Monitor human influenza disease burden
  •  Monitor antigenic drift and other changes (such as antiviral drug resistance) in seasonal influenza viruses
  •  Obtain suitable virus isolates for updating of influenza vaccines
  •  Detect and obtain isolates of new influenza viruses infecting humans, especially those with pandemic potential

Surveillance
Influenza specimens and isolates obtained at WHO National Influenza Centres and Reference Laboratories are forwarded to a WHO Collaborating Centre, where they are analysed for antigenic (immune response), genetic and anti-viral drug sensitivity properties. The data posted by WHO National Influenza Centres is available on the WHO FLUnet website.

Antigenic analysis: Haemagglutination inhibition (HI) assays measure the antigenic relationship between a test virus (Virus X) and a known reference virus (Virus A). Ferret antiserum raised against Virus A is tested for its ability to inhibit agglutination of red blood cells by Virus X, showing whether the haemagglutinin of the test virus has similar receptor-binding specificity to the reference virus, or is potentially a new strain. More detailed information about HI Assays can be found in the HI Diagnostic Kit Information Pamphlet.

Genetic analysis: Representative and antigenically unusual influenza strains are selected for full sequencing of their haemagglutinin and neuraminidase genes. New sequences are phylogenetically classified relative to known sequences, enabling genetic changes and evolution of circulating influenza strains to be tracked. Sequences are submitted to GISAID, an international database for sharing and collaborative use of influenza data.

Anti-viral drug sensitivity: Circulating viruses are tested for their sensitivity to influenza drugs that are both currently in use and in late-stage development. This monitoring enables WHO GISN to identify the emergence of drug-resistant influenza viruses that could present future treatment challenges.

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Vaccine development
Surveillance data about the circulating viruses are continually collected at WHO Collaborating Centres throughout the year. These data provide information about the predominant influenza viruses currently spreading and circulating in different parts of the world. Twice a year a WHO committee meets to consider the data and recommend suitable strains to be included in the next seasonal influenza vaccines.

February: vaccines for the following Northern Hemisphere winter (November-April)

September: vaccines for the following Southern Hemisphere winter (March-October)

These recommendations are made 5-6 months ahead of vaccine release to allow time for production.

In each individual country, national authorities make the final decision on vaccine composition, usually in consideration of the WHO recommendation. In Australia, this decision is undertaken by the Australian Influenza Vaccine Committee (AIVC) at the Therapeutic Goods Administration (TGA).

WHO Global Influenza Virological Surveillance website
WHO Recommendations for Seasonal Vaccines
CDC Information on Vaccine Selection

Information for laboratories with influenza samples to send to a WHO Collaborating Centre is available here.

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