Research Summary

COVID-19 Booster, Seasonal Influenza Vaccine Coadministration Found Safe, Effective in Protection Against Viruses

In a prospective cohort study of health care workers from a large tertiary medical center in Israel, researchers found that receiving the COVID-19 and seasonal influenza vaccines at the same time was not associated with inferior immune response or more frequent adverse events compared with those who only received the COVID-19 vaccine, supporting the coadministration of these vaccines.

In the early days of the pandemic, public health organizations advised against receiving the COVID-19 and seasonal influenza vaccinations at the same time. However, during the 2022 to 2023 influenza season, the CDC, for example, changed course and recommended the coadministration of these vaccines.

While several studies have previously published on the safety and efficacy regarding the coadministration of the COVID-19 and influenza vaccines, little is known about whether coadministration of seasonal influenza vaccines with a booster dose, specifically the omicron BA.4/BA.5–adapted bivalent booster, is as safe and effective as the COVID-19 vaccine alone.

Gonen and colleagues compared the reactogenicity and immunogenicity of patients receiving the omicron BA.4/BA.5–adapted bivalent booster and influenza vaccine at the same time to both the influenza vaccine and COVID-19 vaccination alone between September 2022 and late December 2022.

The researchers divided the study participants into two cohorts for two separate analyses. The reactogenicity analysis included 588 participants (85 in the COVID-19 vaccine-alone group; 357 in the influenza vaccine-alone group; and 146 in the coadministration group). The immunogenicity analysis group included 151 participants (74 in the COVID-19 vaccine group and 77 in the coadministration group).

Gonen and colleagues assessed reactogenicity using adverse reaction questionnaires sent up to 62 days after vaccination. The primary outcome was post-vaccination symptoms. They also evaluated immunogenicity by assessing participants’ serology tests up to 40 days before and 6 to 70 days after COVID-19 vaccination alone or along with the seasonal influenza vaccine. The primary outcome was postvaccination anti-spike IgG titers.

The researchers found that the frequency of systemic reactions was 27.4% (95% confidence interval [CI], 18.2%-38.2%) in the COVID-19 vaccination-alone group, 12.7% (95% CI, 9.5%-16.7%) in the influenza vaccination-alone group, and 27.6% (95% CI, 20.5%-35.6%) in the coadministration group.

Additionally, the risk for systemic symptoms was similar in the coadministration group when compared with the COVID-19 vaccination-alone group (odds ratio = 0.82; 95% CI, 0.43 to 1.56). In the coadministration group, geometric mean titers were estimated to be 0.84 (95% CI, 0.69 to 1.04) times lower than in the COVID-19 vaccine-alone group.

 The main limitation for this study was the lack of generalizability because the study participants were generally healthy health care workers.

“In this cohort study of health care workers who were vaccinated with the omicron BA.4/BA.5–adapted bivalent vaccine, an influenza vaccine, or both, we found that coadministration did not lead to a substantially inferior immune response or to an increased rate of reactogenicity events compared with the administration of this COVID-19 vaccine alone,” the researchers concluded.

Gonen T, Barda N, Asraf K, et al. Immunogenicity and reactogenicity of coadministration of COVID-19 and influenza vaccines. JAMA Netw Open. 2023;6(9):e2332813. doi: 10.1001/jamanetworkopen.2023.32813