Early on in the vaccine rollout, when doses were scarce and COVID-19 cases were skyrocketing, medical experts considered allowing patients to mix and match the Pfizer and Moderna vaccines.
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It was discussed only as "a last-ditch effort if there was an issue with supply lines," says Arizona Medical Association president Dr. Ross Goldberg.
Both vaccines are mRNA based, but Dr. Goldberg stresses that there are key differences between the two products. The compounds are slightly different, and the Pfizer vaccine has to be diluted before it's used. Other issues include the timing between the first and second shots.
"COVID-19 vaccines are not interchangeable," according to the U.S. Centers for Disease Control. There's also a lack of research and data when it comes to mixing and matching vaccines.
"Because we had to get these out so quickly, a lot of these questions would have been answered in that eight to ten year period they spend developing it. We just didn't have time, so now we're learning on the fly," says Dr. Goldberg.
While all the vaccines currently in use have not resulted in any widespread safety problems, he says there are still a lot of unknowns and the medical community isn't likely to recommend a change without solid science and data to support it.
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