Recombinant Quadrivalent Flu Vaccine More Effective in Older Adults

A clinical trial comparing the protective efficacy in older adults of a quadrivalent recombinant influenza vaccine (RIV4) with a standard-dose, egg-grown quadrivalent inactivated influenza vaccine (IIV4) during the A/H3N2-predominant 2014-2015 influenza season showed RIV4 provided better protection against confirmed influenza-like illness among older adults.

In the randomized, double-blind, multicenter trial of 9,003 participants aged 50 and older, 8,855 (98.4 percent) received a trial vaccine and underwent an efficacy follow-up (the modified intention-to-treat population), and 8,604 (95.6 percent) completed the per-protocol follow-up (the modified per-protocol population). Among RIV4 recipients, the reverse-transcriptase polymerasechain-reaction-confirmed, protocol-defined, influenza-like illness attack rate was 2.2 percent (96 cases among 4,303 participants) in the modified per-protocol population, and 2.2 percent (96 cases among 4,427 participants) in the modified intention-to-treat population. Among IIV4 recipients, the attack rate was 3.2 percent (138 cases among 4,301 participants) in the modified per-protocol population and 3.1 percent (138 cases among 4,428 participants) in the modified intention-to-treat population. A total of 181 cases of influenza A/H3N2, 47 cases of influenza B and six cases of nonsubtypeable influenza A were detected. These results show the probability of influenza-like illness was 30 percent lower with RIV4 than with IIV4. The safety profiles of the vaccines were similar.