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The experts are sounding warnings about coronavirus variants. Here’s what you need to know.

Residents 75 and over were able to get coronavirus vaccinations at Fenway Park in Boston on Monday. The looming threat of new coronavirus variants has underlined the need to get millions of shots into people's arms.Suzanne Kreiter/Globe staff

New variants of the coronavirus are making headlines, with experts warning that they could fuel another surge in the pandemic. Here’s what you need to know about the latest developments:

What are coronavirus variants?

The variants are mutations of the coronavirus. Scientists say there’s nothing new about a virus mutating. Viruses constantly mutate naturally as they replicate and circulate in their hosts. “Sometimes new variants emerge and disappear. Other times, new variants emerge and persist,” the US Centers for Disease Control and Prevention says. The CDC is monitoring three variants, from Britain, South Africa, and Brazil.

Are the variants more transmissible and why is that a problem?


The CDC says the variants “seem to spread more easily and quickly.” The problem is that, even if the disease that people get from the variant is not more severe, more transmissibility may lead to more cases. And more cases of the illness would lead to more hospitalizations, more deaths, and more strain on health care systems.

What’s the latest on the British variant?

The British variant could become the dominant strain in the United States by March and lead to a surge of cases and deaths, the CDC has estimated.

The variant has an infection rate 25 percent to 40 percent higher than that of other forms of the coronavirus, Public Health England estimated in its latest analysis. Adding to the concern: Some preliminary evidence suggests that the variant may also be more deadly.

Pfizer and Moderna, which make the only two vaccines currently approved in the United States, have said they believe their vaccines will work against the variant. In the latest piece of worrisome news, though, scientists say the British variant has picked up another mutation -- at least in a few cases -- that appears to make the variant more resistant to vaccines.


Why are people also talking about the the South African and Brazilian variants?

While the British variant may sweep through the United States soon, experts are also worried about the variants from South Africa and Brazil.

In the case of both those variants there is a concern that they contain mutations that make them able to fully or partially evade antibodies, said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center.

That leads to two problems: people who have recovered from a coronavirus infection could get infected again by the variant, and people who have received a vaccination may find it doesn’t work against the variant, said Barouch, who helped develop Johnson & Johnson’s new vaccine, which could be submitted for FDA approval this week.

John Moore, a professor of microbiology and immunology at Weill Cornell Medical College, told CBS News Monday that the South African variant was “particularly troubling” because it “could reduce the efficacy of the vaccines, not catastrophically, but, to an extent, and it’s an extent that we would rather not see happen.”

Barouch noted that the Johnson & Johnson vaccine was 89 percent effective in preventing severe disease and 100 percent effective in preventing hospitalization and death in the arm of the trial that was conducted in South Africa.

How many cases of these variants have been detected in the US and Massachusetts?

Five cases of the British variant have been found in Massachusetts, while no cases have been found of the South African or Brazilian variant.


The CDC says on its variant tracking page that 467 cases of the British variant have been found in 32 states, while three cases of the South African variant have been found in two states, and one case of the Brazilian variant has been found. The numbers are being updated every few days. And the CDC is promising to step up its efforts to detect the spread of the variants.

How worried should we be?

“I think these variants warrant serious study. So far they don’t warrant alarm,” said Barouch.

Ellie Murray, an epidemologist at Boston University said in a tweet Tuesday, “Lately, when I talk to reporters, they expect me to be very worried about COVID variants. But I’m not. Why? Because we know what works to control COVID & we know what uncontrolled transmission looks like. I’m not worried about the variants. I’m worried about the lack of action.”

Others are sounding a more ominous note. Prominent epidemiologist Michael Osterholm recently likened the impending arrival of a coronavirus variant in the United States to a Category 5 hurricane approaching the coast.

“You and I are sitting on this beach where it’s 70 degrees, perfectly blue skies, gentle breeze. But I see that hurricane ... Category 5 or higher 450 miles offshore,” Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said Sunday on NBC’s “Meet the Press.”


“That hurricane’s coming,” said Osterholm.

What can we do about it?

Making sure people get vaccinated, developing booster shots, and continuing to practice social distancing and other public health measures will be key to combat the variants, experts say.

“We need to vaccinate the population of our country and the world as fast as possible,” said Barouch. “We should do that to make sure we stay ahead of the curve.”

“As long as the virus continues to replicate unchecked in human populations in the world, then the world remains susceptible to the risk of the emergence of new variants that potentially could be even more worrisome than the current ones,” he said. “The best way of stopping the virus from developing new variants is to vaccinate the population and reduce the scope of the pandemic.”

The rise of variants will also probably require vaccines to be “updated and revised,” said Barouch. Moderna and Pfizer have already said they are looking into booster shots to protect against variants.

Experts and public health officials also say everyone should continue to wear masks, remain physically distant from others — especially indoors — and continue washing their hands regularly. Some also have questioned whether now is the time to loosen pandemic restrictions.

“What variants are telling us is that the virus is wily: it has the potential [to] evade our defenses. That’s why we must act urgently to tamp down spread as we also ramp up vaccinations,” Dr. Tom Frieden, a former CDC director, said in a tweet Tuesday.


Material from Globe wire services and previous Globe stories was used in this report.

Martin Finucane can be reached at martin.finucane@globe.com.