Update on influenza monitoring and vaccine development

Abstract

Influenza causes substantial morbidity and mortality annually. Vaccination is the most practical means available to control this burden. Global virological surveillance, coordinated by the World Health Organization, is conducted year-round to monitor antigenic and genetic changes to the virus that may affect vaccine performance. However, recently vaccine effectiveness estimates have been low for at least one of the 4 components of the vaccine. Currently-available influenza vaccines suffer several problems. First, current influenza vaccines do not provide long-term protection because they target a surface protein of the virus which undergoes frequent antigenic change, thus requiring annual reformulation. Second, vaccines take many months to manufacture, so an updated formulation contains representative viruses that circulated at least 9 months prior. Third, vaccine may induce a narrow repertoire of antibodies that fail to protect against the broad range of circulating wild-type viruses. Fourth, most vaccines are developed using embryonated hen’s eggs, but rapidly acquire egg-adaptation mutations that alter antigenicity; the antibodies produced may be focused towards egg-grown not wild-type viruses providing limited protection. Finally, repeated, annual vaccination may exacerbate antibody focusing. This presentation will discuss current efforts to overcome these limitations and improve vaccine effectiveness.