CDC guidance on mixing Pfizer and Moderna vaccines in 'exceptional situations'

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The US Centres for Disease Control and Prevention (CDC) has updated its guidance on the coronavirus vaccines in circulation, green-lighting doctors to mix shots from Pfizer and Moderna in “exceptional situations.” The Hill reports that the vaccines, which both use messenger RNA (mRNA) technology, require two doses and were authorised 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 as many as six weeks to get a second dose of either shot. It 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 the effectiveness of either shot.


CDC report summary
The Advisory Committee on Immunization Practices (ACIP) has issued interim recommendations for the use of Pfizer-BioNTech and Moderna COVID-19 vaccines for the prevention of coronavirus disease 2019 (COVID-19) in the US. Both vaccines are lipid nanoparticle-formulated, nucleoside-modified mRNA vaccines encoding the prefusion spike glycoprotein of SARS-CoV-2, the virus that causes COVID-19.

These interim CDC clinical considerations are informed by data submitted to the Food and Drug Administration (FDA) for Emergency Use Authorisation (EUA) of the vaccines, other data sources, general best practice guidelines for immunisation, and expert opinion.

These considerations for mRNA vaccines only apply to the currently authorized vaccine products in the US (Pfizer-BioNTech and Moderna COVID-19 vaccines). Considerations will be updated as additional information becomes available and/or if additional vaccine products are authorised.

In addition to the following considerations, the EUA conditions of use and storage, handling, and administration procedures described in the prescribing information should be referenced when using the Pfizer-BioNTech external icon and Moderna external icon COVID-19 vaccines.


Full report in The Hill (Open access)


CDC report

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