Method: This clinical trial was conducted during the 2011-12 and 2012-13 influenza seasons. At baseline, 205 eligible consented subjects provided a venous blood sample for hemagglutination inhibition (HI) titers and randomly received SD or HD inactivated influenza vaccine. One month later, blood sampling was repeated. Geometric mean titers (GMTs) and 2-sided 95% confidence intervals (CIs) were calculated. An upper bound <1.5 of the 2-sided 95% CI on the ratio of post-vaccination GMTSD to GMTHD indicated non-inferiority. A lower bound ≥1.0 of the 2-sided 95% CI on the ratio of GMTHD to GMTSD indicated superiority. Non-inferiority and superiority tests were performed separately for the 2011-12 and 2012-13 vaccine formulations because the vaccines contained different A/H3N2 and B strains.
Result: The completion rate was 82.4% (169/205), including 56 participants in 2011-12 and 113 participants in 2012-13; 34 subjects participated both years. Mean age of participants was 86.7 years; 71% were ≥85 years. Most participants were white (99%) and female (68%). Demographic profiles of both groups were similar. HD vaccine produced GMT responses to the A/H1N1, A/H3N2, and B strains that were non-inferior to those induced by SD vaccine during both influenza seasons; moreover, HD vaccine induced superior antibody responses to all three strains in 2011-12, and to the A/H3N2 and B strains in 2012-13.
Conclusion: HD influenza vaccine produces non-inferior HI titer responses for A/H1N1, A/H3N2, and B strains among frail elderly nursing home residents. Superiority of HD influenza vaccine was demonstrated for all strains except A/H1N1 in 2012-13, perhaps because 30% of subjects (34/113) participated in both seasons when the A/H1N1 strains were identical.
R. K. Zimmerman,
Sanofi: Grant Investigator, Research grant
T. Ross, None
S. Saracco, None
D. Nace, Sanofi Pasteur: Grant Investigator, Research grant