The risk for solicited reactions following influenza vaccine is higher for women than men, according to research published online Sept. 28 in the Journal of Epidemiology & Community Health.

Marilou Kiely, Ph.D., from the University of Montreal, and colleagues obtained data from phase 3 randomized controlled trials to explore sex differences in adverse events following seasonal influenza vaccines. Risk ratios (RRs) comparing solicited reactions in women versus men were pooled; the risk for bias and I² statistic for heterogeneity was assessed. The main analysis was stratified into younger and older cohorts (18 to 64 years and 65 years and older).

Data were included for 34,343 adults from 18 studies (12 with individual-level data and six with aggregate data). The researchers found that the risk for injection site reactions was higher in women versus men for both younger and older participants, with RRs of 1.29 and 1.43, respectively. For systemic reactions, the risk in women was also higher, with RRs of 1.25 and 1.27 for younger and older participants, respectively. The risk for severe reactions was also elevated in women, with higher RRs in younger versus older participants for systemic reactions (RRs, 2.12 and 1.48, respectively). No variation was seen in RRs between quadrivalent and trivalent vaccines.

“We found a higher risk of solicited reactions following influenza vaccines in females compared with males,” the authors write. “Transparent disclosure of this risk could increase the trust in public health authorities and limit vaccine hesitancy.”