Close-up image of vaccination being given in upper arm of older individual

Influenza and COVID-19 vaccinations are safe and effective when given at the same time, according to a new trial from the United Kingdom that included adults aged 65 years and older.

Investigators tested six different combinations of COVID-19 and influenza vaccines in more than 600 adults between April and June 2021. Participants were given the second dose of either Pfizer-BioNTech’s or AstraZeneca’s COVID-19 shots or a placebo, together with an age-appropriate flu vaccine. Older adults received adjuvanted, trivalent FluAd. (In the United States, adjuvanted FluAd is now recommended in its quadrivalent form for seniors.)

There were no safety concerns raised and side effects were typical of vaccination, Rajeka Lazarus, Ph.D., of University Hospitals Bristol, and colleagues reported. What’s more, the Pfizer COVID-19 vaccine plus adjuvanted, trivalent FluAd was one of four combinations that spurred robust antibody responses, they added. This combination is similar to one likely to be given to seniors in the United States. 

The trial results should be applicable in many settings, Lazarus and colleagues said. Participants reflected the population most likely to receive both influenza and COVID-19 vaccines. 

The trial is the first to test simultaneous administration of an mRNA COVID-19 vaccine (Pfizer’s) with any other type of vaccine, according to the researchers.

One of the trial’s limitations was that flu shots were paired with the second dose in the series of COVID-19 vaccinations, and not a third, booster dose, the researchers noted. Many older people across Britain and the United States — including most U.S. nursing home residents — received their two COVID-19 vaccine doses early in the vaccine rollout and are most likely to get their influenza vaccine together with a booster shot. 

The trial also did not test live, attenuated or high-dose influenza vaccines. In the United States, the Fluzone High-Dose Quadrivalent shot is the only other influenza vaccine along with adjuvanted quadrivalent FluAd recommended for seniors by the Centers for Disease Control and Prevention.

Full findings were published in the Lancet.