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A Note from the General Manager about Excursions

Vaccines Could Drive The Evolution Of More COVID-19 Mutants

SACHA PFEIFFER, HOST:

The new coronavirus variants have raised concerns about whether vaccines will remain effective against this disease. So far, the vaccines still seem to work. Although, scientists are keeping a close eye on a variant first seen in South Africa. But the vaccines themselves could drive the evolution of more mutants. However, NPR science correspondent Richard Harris reports, that's not cause for alarm.

RICHARD HARRIS, BYLINE: You may have heard that bacteria can develop resistance to antibiotics and, in a worst-case scenario, render the drugs useless. Something similar can also happen with vaccines, though, with less serious consequences. This worry has arisen mostly in the debate over whether to delay a second vaccine shot so more people can get the first shot quickly. Paul Bieniasz, a Howard Hughes investigator at the Rockefeller University, says that gap would leave people with only partial immunity for longer than necessary.

PAUL BIENIASZ: They might serve as sort of a breeding ground for the virus to acquire new mutations.

HARRIS: That's because the virus is always mutating. And if one happens to produce a mutation that makes it less vulnerable to the vaccine, that virus could simply multiply in a vaccinated individual. But even if that happens, that's only one step in the process.

BIENIASZ: What's really unclear and really quite important for the virus to evolve is whether those people let - having been vaccinated and infected, whether they have sufficient levels of virus replication to pass the virus on to other people.

HARRIS: If the vaccine keeps virus levels low, even mutated viruses, the infected person won't produce enough to spread to other people. Unfortunately, at the moment, scientists can't answer the most basic questions about this process. How much does the virus actually replicate inside a person who has been vaccinated with either one dose or two? And how effective is that vaccine at limiting infection enough so that the virus levels stay low and prevent the spread to other people? Andrew Read at Penn State University says, whatever the answers may be, vaccine resistance or escape, as it's called, isn't nearly as scary as bacteria becoming resistant to antibiotics.

ANDREW READ: I know everybody's worried about it. But I would say history shows us that vaccine escape does not erode to zero. It does not erase vaccine protection.

HARRIS: A vaccine may become less potent. But in other cases where this has happened, it still works.

READ: It's often got very strong anti-disease properties. So you get less sick even with the viruses that are around.

HARRIS: And this evolutionary pressure is present for any vaccine that doesn't completely block infection. So it's not just an issue for people who are between their initial shot and a booster. Many vaccines, apparently, including the COVID vaccines, do not completely prevent a virus from multiplying inside someone even though these vaccines do prevent serious illness.

READ: I do think there are a lot of options here for trying to deal with any evolution should it occur.

HARRIS: One thing that helps is that dozens of vaccines are being developed. And more than half a dozen are already in use.

READ: One of the great things about having a lot of vaccine options is we might end up with a population which is heterogeneously vaccinated. You might get the AstraZeneca. And I'm going to get one of the mRNA ones. That'll really help hinder the spread of mutants that are good at any one of those.

HARRIS: A virus that has evolved to get around one vaccine is likely to be stopped by another. And that will limit the spread of mutant strains. Drugmakers are also keeping a close eye on mutants and are already formulating new vaccines that will be more effective if it turns out the original vaccines weaken too much. Paul Bieniasz says, this is not a crisis.

BIENIASZ: We're not going to fall off a cliff tomorrow in terms of vaccine efficacy. What we're likely to see is a slow, steady erosion of efficacy over, perhaps, quite a long period of time.

HARRIS: Bieniasz says, to slow this evolutionary process as much as possible, it's important to slow the spread of the virus right now so people who get vaccinated are at lower risk for getting infected in the first place.

Richard Harris, NPR News.

(SOUNDBITE OF DODO'S "EMANCIPATOR") Transcript provided by NPR, Copyright NPR.