Post-marketing Surveillance of Annual Influenza Vaccines: Extended Vaccine Safety and Immunogenicity Evaluation

Trivalent inactivated vaccines (TIVs) are the principal tools for minimizing seasonal influenza morbidity and mortality in populations at increased risk of adverse outcomes. To keep pace with the evolution of circulating viruses the composition of TIVs is annually updated. Depending upon circumstances, the seasonal formulation may contain 1-3 new variant strains representing Canada's supply of H1N1, H3N2 and B 2009 vaccine. Standardized manufacturing processes favour consistent vaccine safety and immunogenicity profiles from year to year but unanticipated differences can and do occur. As a consequence of the unusual occurrence of "oculorespiratory syndrome" in recipients of a Canadian-made TIV for 2000-2001, the Canadian regulatory agency has required pre-approval clinical testing of seasonal vaccines in adults. This small scale testing (120 subjects) cannot exclude the occurrence of infrequent, troublesome adverse effects. Expanded testing is desirable and would best be done soon after vaccines are approved for distribution so that results could inform the public vaccination programs that follow. Having an established capacity for rapid evaluation of a new influenza vaccine will be invaluable in the event of a pandemic, when vaccines will be less thoroughly tested before being made available to protect the public.

The objectives of this study are two-fold:

1. To assess the safety and immunogenicity of a seasonal TIV influenza vaccine quickly enough to inform subsequent public delivery programs.
2. To use the opportunity to refine preparedness for rapid evaluation of a pandemic influenza vaccine.