While the two authorized Covid-19 vaccines are “not interchangeable,” it may be acceptable to get one dose of each in order to complete both doses, the US Centers for Disease Control and Prevention said in guidance updated Thursday.
The guidance, which comes amid concerns surrounding vaccine supply and distribution, applies to Pfizer/BioNTech’s and Moderna’s vaccines. Both use genetic material called mRNA as the basis for their vaccines.
“In exceptional situations in which the first-dose vaccine product cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses,” the CDC says.
“If two doses of different mRNA COVID-19 vaccine products are administered in these situations (or inadvertently), no additional doses of either product are recommended at this time.”
CDC says the safety and efficacy of switching vaccines hasn’t been evaluated. “Every effort should be made” to keep track of which vaccine people received and ensure they get the same one for their second dose several weeks later, the recommendations say.
The agency says its guidance may be updated as new information and new types of Covid-19 vaccines become available.