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2009 Pandemic Influenza A (H1N1) Vaccine

Publication Summary

The purpose of this evidence review is to consolidate pH1N1 vaccine research (related to both adjuvanted and unadjuvanted formulations) published since the start of the pH1N1 pandemic and to contextualize the findings in a Canadian setting. Specifically, seven aspects will be discussed – efficacy, effectiveness, safety and side effects, recommended dosage, priority sequencing, impact of 2009-2010 seasonal influenza vaccine on pH1N1, and public perception of Canada’s pH1N1 immunization campaign.

Key Points:

  • The pH1N1 vaccines provide unexpectedly good immune responses.
  • Oil-in-water emulsion adjuvants, such as AS03 and MF59, significantly increase immunogenicity of the inactivated split pH1N1 vaccine, allowing a reduction in the dose of hemagglutinin (HA) antigen needed to provide protection.
  • Aluminum adjuvant-based pH1N1 vaccines had limited effects on immune response.
  • Results from a limited number of published and unpublished studies suggest impressive estimates of pH1N1 vaccine effectiveness (VE).
  • The overall safety of the pH1N1 vaccine has been confirmed.
  • These findings support the use of either two doses of unadjuvanted pH1N1 vaccine containing 7.5 µg HA administered 21 days apart or one dose of AS03-adjuvanted pH1N1 vaccine containing 1.9 µg of HA to provide adequate protection in children less than 9 years of age.
  • The inherent trade-off between community-level risk versus individual-level risk warrants recognition.