COVID-19 and seasonal influenza vaccines are essential in preventing respiratory infections and their potentially severe complications. Simultaneous administration of vaccines is efficient and may improve coverage with each vaccine. However, the safety of simultaneous administration of COVID-19 and influenza vaccines has not been well described.

Hause, et al. (2022) sought to evaluate adverse events and health impacts associated with simultaneously administered COVID-19 mRNA booster and seasonal influenza vaccines in the U.S. population.

Of a total of 981,099 persons aged 12 years or older registered with v-safe, simultaneous administration of COVID-19 mRNA booster and seasonal influenza vaccines was reported by 92 023 (9.4%) v-safe respondents; of these respondents, 54 926 (59.7%) were female, 36 234 (39.4%) were male, and sex was unknown for 863 (0.9%). In the week following vaccination, any systemic reactions were reported by 36 144 (58.9%) of 61 390 respondents who simultaneously received Pfizer-BioNTech booster and influenza vaccines and 21 027 (68.6%) of 30633 respondents who simultaneously received Moderna booster and influenza vaccines. Respondents who simultaneously received influenza and Pfizer-BioNTech booster vaccines (aOR, 1.08; 95% CI, 1.06-1.10) or influenza and Moderna booster vaccines (aOR, 1.11; 95% CI, 1.08-1.14) were slightly more likely to report any systemic reaction in the week following simultaneous vaccination than respondents who received only a COVID-19 mRNA vaccine booster.

In this study, compared with administration of COVID-19 mRNA booster vaccines alone, simultaneous administration of COVID-19 mRNA booster and seasonal influenza vaccines was associated with significant increases in reports of systemic reactions during days 0 to 7 following vaccination. These results may help better characterize the outcomes associated with simultaneously administered COVID-19 booster and influenza vaccines in the US population.

Reference: Hause AM, et al. Reactogenicity of Simultaneous COVID-19 mRNA Booster and Influenza Vaccination in the US. JAMA Netw Open. 2022;5(7):e2222241. doi:10.1001/jamanetworkopen.2022.22241