Is it safe or effective to mix Pfizer and Moderna COVID-19 vaccines?

BIRMINGHAM, Ala. (WBRC) - A change of guidance from the Centers for Disease Control on mixing the Pfizer and Moderna COVID-19 vaccines, now says getting two different vaccines is okay but only under “exceptional situations”.

The CDC previously said the Pfizer and Moderna vaccines should not be used together as a first and second dose, but as mass vaccination efforts continue across the country, and the supply of the vaccines was stretched thin, mixing the vaccines may be necessary.

Medical Director of Disease Control at Jefferson County Department of Health Dr. Wesley Willeford explained what situation would call for the vaccines to be mixed.

“There’s no way to get the exact vaccine that you had for your first dose,” said Willeford. “Hopefully, that’s not going to happen because the way these doses are going out, is they’re trying to have the first dose and the second dose tied to it later. This really should be a very rare occurrence.”

Willeford said the risk of mixing the two vaccines appeared minimal but it’s still not a preference and there was little data available.

Willeford said because the Pfizer and Moderna vaccines are both mRNA vaccines in theory they should be as effective when used together.

“I think a big concern is that when the Pfizer study was done and the Moderna study was done, they only used their product. And so, when we say a person gets a 95% protection out of it what that means is, they get 95% protection after having Moderna vaccine times two, or Pfizer vaccine times two. We don’t know what would happen with Moderna followed by Pfizer or Pfizer followed by Moderna,” Willeford explained.