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Ideally, Americans receiving their Pfizer/BioNTech or Moderna COVID-19 vaccines will get both doses from the same manufacturer, said Gregory Poland, MD, a vaccinologist at the Mayo Clinic in Rochester, Minnesota.

After all, that's how they were tested for efficacy and safety, and it was results from those studies that led to emergency use authorization (EUA) being granted by the US Food and Drug Administration.

But states and countries have struggled to keep up with the demand for vaccine, and more flexible vaccination schedules could help.

So researchers are exploring whether it is safe and effective to get the first and second doses from different manufacturers. And they are even wondering whether mixing doses from different manufacturers could increase effectiveness, particularly in light of emerging variants.

It's called the "interchangeability issue," said Poland, who reports that he has gotten a steady stream of questions about it.

Head over to Medscape to read the full story.