A British clinical trial found no sign of danger in getting a flu shot and a second dose of a Covid-19 vaccine at the same time, results that support the advice of U.S. health authorities and are welcome news for strained health care workers as flu season hits.
In the study, doctors recruited 679 people from April to June across Britain. At the time, all of the volunteers had received a first dose of a Covid-19 vaccine, either from AstraZeneca or Pfizer-BioNTech, the two vaccines first authorized there.
When the volunteers returned for a second vaccine dose, the researchers also gave half of them a flu shot and the other half a placebo. The researchers then monitored the volunteers for side effects, such as aches and fevers.
“There are no safety concerns raised in this trial,” the authors wrote in their preliminary report, which was posted online on Thursday and has not yet been published in a scientific journal.
In addition to looking at the safety of the vaccines, the researchers also collected blood to measure antibodies to the coronavirus. Some combinations of different vaccine brands led to a slightly lower level of antibodies, and a slightly higher level in other cases. But the researchers did not suspect that any combination of a flu and Covid vaccine would result in a lower effectiveness than each given individually.
The researchers did not speculate about what immune responses people might experience if they get a flu shot at the same time as a third Covid-19 shot, which many people may be doing as countries authorize boosters.