Study points to safety of simultaneous flu and COVID-19 vaccines

Investigators in the United Kingdom found that concomitant vaccination of flu and COVID-19 raised no safety concerns and preserved the immune response to both vaccines.

Simultaneous administration of flu and the second COVID-19 vaccines is safe, according to a recent study.1

Concomitant vaccination raised no safety concerns and preserved the immune response to both of the vaccines, according to investigators led by Rajeka Lazarus, MD, from University Hospitals Bristol-University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK.

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In addition, the investigators noted, the healthcare burden on the system was reduced.

In this study, adults who had received 1 dose of either the ChAdOx1 (AstraZeneca) or BNT162b2 (Pfizer-BioNTech) COVID-19 vaccines were included in a multicenter study in the UK.

They received either an age-appropriate flu shot (3 flu shots were tested) or placebo with the second COVID-19 vaccine.

The participants who were randomized to placebo received the flu vaccine 3 weeks later and vice versa. The study participants were followed for 6 weeks.

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The primary endpoint was development of 1 or more systemic reactions to the vaccines during 7 days after the first trial vaccination(s) in the 6 possible combinations.

A total of 340 individuals were randomized to receive a flu vaccine and a COVID-19 vaccine, and 339 to receive placebo and a COVID-19 vaccine.

The investigators reported that most reported reactions were mild or moderate, that is, pain at the site of the injections and fatigue.

The rates of local and unsolicited systemic reactions were similar between the randomized groups.

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One serious adverse event occurred, that is, hospitalization with a severe headache, that was considered related to the trial intervention. In addition, the immune responses to the vaccinations were preserved.

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1. Lazarus R, Baos S, Cappel-Porter H, et al. The safety and immunogenicity of concomitant administration of COVID-19 vaccines (ChAdOx1 or BNT162b2) with seasonal influenza vaccines in adults: a phase IV, multicentre randomised controlled trial with blinding (ComFluCOV). Lancet published online September 30, 2021.