Receiving a Flu Shot and Covid Vaccine at the Same Time Is Safe, Study Finds

Mild to moderate side effects were reported, such as fatigue in three-quarters of participants in the research

An image of a older male physican vaccinating a young child. The child is smiling and is being held by her father.
Covid-19 booster vaccines are also safe to receive along with the flu vaccine. However, third doses are currently authorized for Pfizer-BioNTech vaccine recipients who are immunocompromised, have underlying medical conditions, or those 65 years of age or older.

  Marko Geber/Getty Images

According to a clinical trial led by researchers at the University of Bristol, individuals can receive a flu shot and their second dose of a Covid-19 vaccine simultaneously, Carl Zimmer reports for the New York Times. The preliminary results were released as a pre-print study in The Lancet in September and have not yet been peer-reviewed.

Covid-19 booster vaccines are also safe to receive alongside the flu vaccine. However, at this time, third doses are only authorized for Pfizer-BioNTech vaccine recipients who are immunocompromised, have underlying medical conditions, or those 65 years of age or older, reports Kaitlin Sullivan of NBC News.

In the new study's trials, doctors recruited 679 volunteers from April to June at 12 sites in Britain. During the study, all volunteers had received the first dose of a Covid-19 vaccine from either Pfizer-BioNTech or AstraZeneca, per the New York Times. Half of the participants received a flu shot when the groups returned for their second dose of the Covid-19 vaccine, while the other half received a placebo. The vaccines were given on the same day, but administered in different arms. The researchers found that 97 percent of participants were willing to receive two jabs at future appointments.

After receiving their doses of the vaccines, the research team monitored the study groups for fevers or aches. Side effects were mild to moderate in trials with three types of flu vaccines, per Alistair Smout for Reuters.

"This is a really positive step which could mean fewer appointments for those who require both vaccines," says the study's first author Rajeka Lazarus, a vaccinologist at the University Hospital Bristol & Weston, to Reuters.

Blood samples from the participants show that various combinations of flu shots and Covid-19 vaccines given simultaneously do not change either shot's effectiveness compared to receiving each jab separately, reports the New York Times.

Previously, the Centers for Disease Control and Prevention (CDC) recommended spacing out Covid-19 and flu vaccines by 14 days. But the CDC has revised its guidelines and suggests the wait is no longer needed, reports Emma H. Tobin for the Associated Press.

Experts generally recommend staying up to date on vaccines this year because last year's flu season was historically mild since people were staying home and masking up. However, as mask mandates have been lifted and the vaccines have allowed people to return to in-person gatherings, there is no way to tell how intense this year's flu will be, per the AP. 

"The worry is that if they both circulate at the same time, we're going to have this sort of 'twin-demic,'" Richard Webby, a flu expert at St. Jude Children's Research Hospital, tells the AP. "The concern with that is that it's going to put extra strain on an already strained health care system."

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