JAMA Netw Open

Simultaneous vs. sequential flu and mRNA COVID-19 vaccines: Any safety differences?

November 13, 2024

Safety, including reactogenicity, after simultaneous vs. sequential administration of mRNA COVID-19 and inactivated influenza vaccines was comparable. The findings support simultaneous administration of the two vaccines as a means to achieve timely vaccination.

This randomized, placebo-controlled trial, conducted between October 2021 and June 2023, included nonpregnant individuals ≥5 years of age with intention of receiving both influenza and mRNA COVID-19 vaccines. At visit 1, participants were given either IIV4 or saline placebo simultaneously with mRNA COVID-19 vaccine in the opposite arm. Those who received placebo at visit 1 received IIV4 and those who received IIV4 at visit 1 received placebo 1 to 2 weeks later at visit 2. Primary composite reactogenicity outcome was the proportion of participants with fever, chills, myalgia, and/or arthralgia of moderate or greater severity within 7 days after vaccination visits 1 and/or 2.

A total of 335 persons (mean age, 33.4 years) were randomized (169 to the simultaneous group and 166 to the sequential group); 63.0% were female, and 76.1% received bivalent BNT162b2 mRNA COVID-19 vaccine. The primary composite reactogenicity outcome was noninferior in the simultaneous vs. sequential groups (25.6% vs. 31.3%). Respective proportions in each group were similar after each visit separately (visit 1, 23.8% vs. 28.3%; visit 2, 3.0% vs. 5.4%). There were no significant group differences with respect to adverse effects, serious adverse effects, and adverse effects of special interest.

Source:

Walter EB, et al. (2024, November 6). JAMA Netw Open. Safety of Simultaneous vs Sequential mRNA COVID-19 and Inactivated Influenza Vaccines: A Randomized Clinical Trial. https://pubmed.ncbi.nlm.nih.gov/39504023/