Recombinant Influenza Vaccine Could Lower Flu Risk by 30%

A quadrivalent, recombinant influenza vaccine (RIV4) was more effective than a standard-dose, egg-grown, quadrivalent, inactivated influenza vaccine (IIV4) at protecting older adults from the flu, according to a recent study.

The randomized, double-blind trial enrolled 9003 adults who were 50 years of age or older. Participants were randomly assigned to receive either a RIV4 or a standard-dose IIV4, and provided nasopharyngeal swabs if they experienced influenza-like illness symptoms to confirm cases of influenza.
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Of the participants who enrolled in the study, 8855 (98.4%) received a trial vaccine and underwent an efficacy follow-up, and 8604 (95.6%) completed the per-protocol follow-up. Participants who underwent an efficacy follow-up were grouped as a modified intention-to-treat population, and participants who completed the per-protocol follow-up were grouped as a modified per-protocol population.

A total of 96 cases of confirmed influenza occurred among the 4303 RIV4 recipients in the modified per-protocol population, and 96 cases occurred among the 4427 RIV4 recipients in the modified intention-to-treat population. The influenza attack rate for both groups was 2.2%.

Among the 4301 IIV4 recipients in the modified per-protocol population, a total of 138 cases of confirmed influenza occurred (influenza attack rate was 3.2%). A total of 138 cases of confirmed influenza occurred among the 4428 IIV4 recipients in the modified intention-to-treat population (influenza attack rate was 3.1%).

Influenza A/H3N2 was detected in 181 cases, influenza B was detected in 47 cases, and nonsubtypeable influenza A was detected in 6 cases.

Overall, the researchers found that RIV4 recipients had a 30% lower risk of acquiring an influenza-like illness compared with IIV4 recipients, which satisfied the prespecified criteria for the primary noninferiority analysis and an exploratory superiority analysis of RIV4 over IIV4.

“RIV4 provided better protection than standard-dose IIV4 against confirmed influenza-like illness among older adults,” the researchers concluded.

—Melissa Weiss

Reference:

Dunkle LM, Izikson R, Patriarca P, et al. Efficacy of recombinant influenza vaccine in adults 50 years of age or older [published online June 22, 2017]. N Engl J Med. doi:10.1056/NEJMoa1608862.