The More Things Change, the More They Stay the Same...
March 26, 2021 10:53 AM

Has either (or both) of the Pfizer and Moderna vaccines formula changed over time. That is, if I got the vaccine tomorrow would I be getting the exact same formula as the person who got it first (once available to the public -- I think it was a nurse in NY)? Or, does the formula change slightly to take into account current data or current variants of the virus?
posted by AugustWest to Science & Nature (8 answers total) 2 users marked this as a favorite
The formulae have not changed from the first doses administered in trials (March 16 2020 in the case of Moderna, i.e. mRNA-1273). If it did it would need to be reapproved by the FDA in the US and the equivalent agencies elsewhere.
posted by caek at 10:57 AM on March 26, 2021


If it changes, they'd have to recertify the vaccine, unless they can prove the changes are so minor it can't make things any worse.
posted by kschang at 10:58 AM on March 26, 2021


In the US, Sandra Lindsay rec'd the first public Pfizer vaccine [BNT162b2] in December, and it's the same formula recently lab-tested against newer variants.
posted by Iris Gambol at 11:04 AM on March 26, 2021


By the way, you can read the "formula" of the active bits of the two mRNA vaccines if you're interested: Moderna, Pfizer/BioNTech.
posted by caek at 11:05 AM on March 26, 2021


Follow-up: The flu vaccine changes every year is my understanding. Do those vaccines have to go through trials every year to certify them?

Thank you for the quick responses.
posted by AugustWest at 11:07 AM on March 26, 2021


Flu vaccines are revised yearly. Manufacturers do their own tests, and FDA approves them by lots.
In the United States, licensed influenza vaccine manufacturers must submit a supplement to their license for review and obtain FDA approval before the updated version of the influenza vaccine containing new virus antigens can be distributed.
Link
posted by kschang at 11:12 AM on March 26, 2021


Thank you!
posted by AugustWest at 12:29 PM on March 26, 2021


BTW they are putting in place similar mechanisms for the various adapted vaccines which are now being developed, at least some of which have started human trials, in order to approve variant-adapted versions quickly.
posted by atrazine at 2:20 PM on March 26, 2021


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