No Double Whammy of Side Effects From Dual COVID-Flu Jabs

Patients receiving a COVID-19 mRNA booster vaccine were more likely to report mild systemic reactions if they were simultaneously vaccinated against seasonal influenza, a study showed.

Data from the CDC’s v-safe program showed more reports of symptoms in the 7 days after concurrent receipt of a flu vaccine with either the Pfizer-BioNTech booster (adjusted OR 1.08, 95% CI 1.06-1.10) or the Moderna booster (adjusted OR 1.11, 95% CI 1.08-1.14) compared with people who received either booster alone, reported Anne Hause, PhD, of the CDC in Atlanta, and colleagues.

However, the excess systemic reactions resulted in mostly mild symptoms including fatigue, headache, and myalgia, according to the retrospective cohort study in JAMA Network Open.

What’s more, a nocebo effect may have been at play given the study’s nonrandomized nature and reliance on a self-report registry, according to Kathryn Hall, PhD, MPH, molecular biologist at Brigham and Women’s Hospital in Boston, and colleagues.

“Thus, while messaging could include the fact that serious reactions are rare even when the vaccines are given concomitantly, in light of these data, clinicians can confidently inform patients that concurrent administration of the COVID-19 booster and seasonal influenza vaccine is both safe and associated with only a slight increase in adverse events compared with the COVID-19 booster alone,” Hall and co-authors wrote in an accompanying editorial.

Hause’s group noted that both COVID-19 and influenza vaccines are important for respiratory health and suggested that receiving both vaccines together may improve coverage for each other.

Some physicians are currently recommending that people get COVID-19 booster shots as soon as possible, even during the summer, as highly-transmissible BA.5 becomes the dominant variant in the U.S.

At the same time, however, the country’s flu vaccination program is faltering during the pandemic, according to Hall and colleagues.

“Nationally, during the 2020 to 2021 season, influenza vaccination coverage was only 50.2%. Significant disparities have also been noted by race and ethnicity. Influenza results in significant morbidity annually which could be averted by increased vaccination coverage,” according to the editorialists.

Ultimately, they urged “the development of public health campaigns to increase dual vaccination.”

The cohort study used self-reported data from 981,099 people after vaccination. Data was collected from September 22, 2021 to May 1, 2022 via the voluntary application v-safe, a smartphone based monitoring system established by the CDC.

Study authors did not collect data on influenza vaccines alone as they are considered to not be particularly reactogenic.

Limitations of the study included the questionable generalizability of the results to the general population. Furthermore, v-safe was not designed to collect data on rare, unsolicited adverse events, and there were no records on the type of influenza vaccine used, according to Hause’s group.

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