“Vaccine mixing” studied in the UK


AUGUSTA, Ga. (WJBF)– New COVID-19 vaccine research from the U.K. looks at “vaccine mixing”– receiving your first dose of the shot from one brand, and the second dose from a different one. In the study, participants received one shot of the Pfizer vaccine and one from AstraZeneca, which is not available in the U.S.

Dr. Ioana Chirca, infectious disease physician at University Hospital, says the practice may be a way to combat vaccine supply issues.

“There is a lot of traveling now that has started back some. People get one dose of a vaccine abroad and then they come here, or the other way around,” Dr. Chirca said. “So say they got AstraZeneca in Europe and now they’re here and they’re due for their second shot– we don’t have AstraZeneca here– so the question does come up, is it okay to take Pfizer or Moderna?”

She says it may be a way to help those who, while abroad, received a dose of a shot not available in the US.

“I think we will see more of these mixing studies and I think it will give us even greater confidence that we are doing the right things when we may be recommending perhaps to someone who’s coming from abroad, okay you took the AstraZeneca or another kind of vaccine, okay you can go ahead and get the second dose Pfizer or Moderna,” Dr. Chirca said.

Vaccine mixing is not recommended by the CDC, and study participants who mixed vaccines reported more side effects like fever, fatigue, and chills, than those who received two doses of the same shot.

“There’s no data that getting a mix will give you any more protection than two of the same ones,” infectious disease physician at AU Health, Dr. Rodger MacArthur said. “And again, what they found in Europe is that AstraZeneca followed by Pfizer actually gives you more side effects. So right now stick with two doses of either Moderna, or two doses of Pfizer, or one dose of Johnson & Johnson.”

Infectious disease experts say there just isn’t enough data to support vaccine mixing at this time. But they say we do know the vaccines we already have are effective.

“You already have highly effective vaccines. The mRNA vaccines, both Pfizer and Moderna are highly effective,” Dr. Chirca. “You have 80% effectiveness of the one dose and 95% for the second dose. So the question is how much more, how much higher can you get, even if you mix them.”

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