New mutations raise specter of ‘immune escape’
When the number of COVID-19 cases began to rise again in Manaus, Brazil, in December 2020, Nuno Faria was stunned. The virologist at Imperial College London had just co-authored a paper in Science estimating that three-quarters of the city's inhabitants had already been infected with SARS-CoV-2, the pandemic coronavirus—more than enough, it seemed, for herd immunity to develop. The virus should be done with Manaus. Yet hospitals were filling up again. “It was hard to reconcile these two things,” Faria says. He started to hunt for samples he could sequence to find out whether changes in the virus could explain the resurgence.
https://science.sciencemag.org/content/371/6527/329
Some scientists worry that proposed changes in vaccine dosing regimens could hasten the evolution of such strains. Desperate to tame a massive surge in cases, the United Kingdom on 30 December decided to allow up to 12 weeks between the first and second dose of two authorized vaccines, rather than the 3 or 4 weeks used in the vaccines' clinical trials, so more people can get their first dose quickly and have at least some immunity. And the Trump administration decided to ship all available doses immediately, rather than holding back 50% to guarantee that people receive their second doses on time. That policy, which the Biden administration has said it will follow, could inadvertently extend the dosing interval if future vaccine deliveries don't arrive or aren't administered on time.
Widespread delays of the second dose might create a pool of millions of people with enough antibodies to slow the virus and avoid getting sick, but not enough to wipe it out. That could well be the perfect recipe for creating vaccine-resistant strains, says virologist Florian Krammer of the Icahn School of Medicine at Mount Sinai: “If we end up with everybody just getting one dose with no doses available for a timely boost, that would in my opinion, be a problem.”
If vaccine-resistant SARS-CoV-2 strains emerge, vaccines might need to be updated. Several vaccines could be easily changed to reflect the latest changes, but regulators might balk at authorizing them without seeing updated safety and efficacy data, Krause says. If new variants circulate alongside older strains, multivalent vaccines, effective against several lineages, might even be needed. “To be clear: These are downstream considerations,” Krause says