Deviating From CDC Guidelines, Britain Authorizes “Mix-And-Match” Vaccinations

The Centers for Disease Control and Prevention (CDC) authorized the COVID-19 vaccines under guidelines that the vaccines “are not interchangeable,” and that “the safety and efficacy of a mixed-product series have not been evaluated” according to a report in Deviating from CDC guidelines, Britain officials have authorized the use of “mix-and-match” vaccinations.  Under Britain’s new guidelines a different COVID-19 vaccine can be administered when the second dose of the initial COVID-19 vaccine is unavailable.

Britain’s vaccination program was updated amid fears of a new, more transmissible strain of the COVID-19 virus and problems in vaccine rollout.  According to, Britain’s new guidance specifies that “every effort should be made” to complete a dosing regimen with the same shot first used”. But British officials say its OK to give a person another manufacturers vaccine if the vaccinated person doesn’t know the name of the manufacturer of their original shot, or if the person’s original vaccine isn’t available.

British officials have issued an “emergency green light” to two vaccines, Pfizer and AstraZeneca. reports that while both Pfizer’s and AstraZeneca’s vaccines introduce the spike protein, their ingredients differ. Pfizer’s vaccine relies on messenger RNA, or mRNA and AstraZeneca’s shots delivers DNA, a cousin of mRNA, according to Deviating from the vaccine dosage regimen tested in late-stage clinical trials may have unknown consequences.

Some scientists say Britain is gambling with its new guidance. “There are no data on this idea whatsoever” said John Moore, a vaccine expert at Cornell University. Britain “seem to have abandoned science completely now and are just trying to guess their way out of a mess” he said. “None of this is being data driven right now” said Dr. Phyllis Tien, an infectious disease physician at the University of California, San Francisco. “We’re kind of in this Wild West’ said Dr. Tien.


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