Influenza is a highly contagious respiratory disease and epidemics of influenza cause substantial morbidity and mortality worldwide. The Advisory Committee on Immunization Practices (ACIP) recommends influenza vaccination for all persons 6months of age and older who do not have contraindications. The seasonal influenza vaccine requires frequent updates due to the constant evolution of influenza viruses resulting in antigenic drift.

As a World Health Organization Collaborating Centers (WHO CC) for Reference and Research on Influenza and a member of the Global Influenza Surveillance Network, the Centers for Disease Control and Prevention (CDC) closely monitors the genetic and antigenic evolution of circulating influenza viruses. The five WHO CCs meet twice each year to recommend the virus strains composition for the upcoming season’s influenza vaccine. The meeting is held every February for the northern hemisphere influenza vaccine recommendations and every September for the southern hemisphere influenza vaccine recommendations. Epidemiological, genetic, antigenic, as well as serological data are critical in guiding vaccine recommendations.

CDC is seeking pre- and post- influenza immunization sera panels from six age cohorts, young pediatric (6 to 35months), older pediatric and adolescent (3 to 8years old and 9 to 17 years old), adult (18 to 49 years old), older adult (50 to 64 years old) and elderly (65 years or older) populations to determine if antibodies induced by the current influenza vaccine effectively inhibit currently circulating influenza viruses. The ability of antibodies in post-influenza vaccine serum samples to inhibit hemagglutination or to neutralize currently circulating influenza viruses is a measure of how effective the current vaccine will be at inducing protective antibodies against circulating influenza viruses.

All sera panels will be tested by hemagglutination inhibition (HI),microneutralizaiton (MN) assays and other immunological assays to evaluate the immune response induced by the current influenza vaccines to newly circulating viruses. HI and MN results will also be analyzed to compare the seroconversions or four-fold rise in titers between pre- and post-vaccination sera induced by the current influenza vaccine to titer response rises demonstrated against newly circulating viruses.

In addition, CDC is seeking large volume post-influenza immunization sera from adult donors for use in hemagglutination inhibition, virus neutralization, and other relevant immunological assays for antigenic characterization of virus isolates submitted to CDC for surveillance and characterization of immune responses following influenza vaccination.

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