What to Know About Delayed Vaccine Doses and the Potential for Mutation

Some scientists have raised concerns about ‘escape mutants’

Yasmin Tayag
Medium Coronavirus Blog
4 min readJan 7, 2021

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Photo by CDC on Unsplash

The U.K. recently made the controversial decision to delay administration of the second dose of the Covid-19 vaccines. The U.K. has approved vaccines from Pfizer/BioNTech, Moderna, and Oxford/AstraZeneca, all of which require two doses, administered at least 21 days apart. The decision will allow the doses to be administered up to 12 weeks apart.

This choice is controversial for a number of reasons. Critics argue that the data from the clinical trials don’t support such a move, and it’s not known what will happen if the protocols are changed. Though U.K. medical officers argue that the first dose will provide the “majority” of immunity, some say this partial protection may not be enough. Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, has advised against delaying the second dose in the U.S.

Some have raised the concern that delaying the second dose of the vaccine could create conditions that lead to a vaccine-resistant strain of the virus. On January 1, Rockefeller University virology professor Paul Bienasz, PhD, tweeted a document with the caption “Musings of an anonymous pissed off virologist,” in which he criticized the plan to delay the second dose because of its potential to lead to a vaccine-resistant strain of SARS-CoV-2. Here’s a passage from the full piece, a tongue-in-cheek missive sarcastically explaining how one might create a such a mutant:

Finally, and here’s the kicker: having developed a remarkable two-dose vaccine, that is extraordinarily effective, ADMINISTER IT TO MILLIONS OF PEOPLE — BUT DELAY THE SECOND DOSE. Generating a pool of hosts with just the right amount of neutralizing antibody to apply selection pressure, but also maintain sufficient levels of partially antibody-resistant virus to allow onward transmission is key here. We might not achieve this shortly after the first dose, but if we let immunity wane for a little while, say 4 to 12 weeks, we just might hit the sweet spot.

Retweeting Bienasz, virologist Angela Rasmussen, PhD wrote: “The real ticking time bomb is the selection pressure of an incomplete vaccine dosing regimen.”

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Yasmin Tayag
Medium Coronavirus Blog

Editor, Medium Coronavirus Blog. Senior editor at Future Human by OneZero. Previously: science at Inverse, genetics at NYU.