CDC changes COVID-19 vaccine guidance to allow mixing Pfizer, Moderna shots in ‘exceptional situations’

The Centers for Disease Control and Prevention (CDC) on Friday updated its guidance on the coronavirus vaccines in circulation, green-lighting doctors to mix shots from Pfizer and Moderna in “exceptional situations.”

The vaccines, which both use messenger RNA (mRNA) technology, require two doses and were authorized to be administered 21 and 28 days apart, respectively. The CDC now says patients can receive either shot as long as they are given at least 28 days after the first dose.

The updated guidance also says it’s OK to wait up to six weeks to get a second dose of either shot.

Don’t get carried away, though: The guidance underscores that the two shots are not interchangeable and that the CDC has not fully studied whether mixing and matching the two vaccines would impede on the effectiveness of either shot.

“The intent is not to suggest people do anything different, but provide clinicians with flexibility for exceptional circumstances,” Jason McDonald, a spokesman for CDC, told CNBC.