UK COVID variant more transmissible but may not be more deadly, new studies indicate

Two new British studies suggest that the B.1.1.7 variant is more transmissible than the original COVID-19 variants; however, it does not appear to be more deadly or cause more severe symptoms.

One of the studies, published in The Lancet Public Health, also reported a low rate of reinfection with B.1.1.7 in those who have recovered from previous COVID infections.

As was predicted, the Centers for Disease Control and Prevention is now reporting the B.1.1.7 strain to be the most dominant variant in the U.S., accounting for over 30% of cases in some states.

But B.1.1.7 isn't the only new, more contagious variant to emerge in recent months. Other so-called "variants of concern" include a variant first identified in South Africa (B.1.351) and a variant first identified in Brazil (P.1), according to the CDC.

Both B.1.351 and P.1 have taken over in South Africa and Brazil, respectively, and both have been found in low numbers in the United States. So why is the B.1.1.7 U.K. variant sweeping the country?

Experts say it's possible that B.1.1.7 is spreading in the U.S. because it is more contagious than original strains. It's also likely that B.1.1.7 had a head-start in the U.S., effectively edging out the other more contagious variants before they had a chance to take hold.

"What we have seen across the globe is that more easily transmissible variants will ... outcompete those variants that don't spread as easily," said Dr. John Brownstein, the chief innovation officer at Boston Children's Hospital and an ABC News contributor.

According to Brownstein, B.1.1.7 was able to spread quickly because it entered the country before immunization became widespread.

In terms of whether B.1.1.7 will outcompete other major variants, epidemiologist Dr. Emily Martin, of the University of Michigan, said, "It depends on which variant reaches a group of people first, for example B.1.1.7 was the first to start spreading in Michigan,"

Experts still aren't sure why some viral variants are more contagious than others.

One idea is that they can create a more significant viral load, meaning they can produce higher levels of virus in your nose, creating a greater opportunity for the virus to spread. It's also possible that these variants are better at latching onto or getting into cells, meaning someone exposed to the virus is more likely to become infected.

The good news, experts say, is that current vaccines and public health measures appear to be effective against B.1.1.7.

"We can develop vaccines that are closer to the variants, but it seems that so far we have effective vaccines," said Dr. Gigi Gronvall, an immunologist and associate professor of environmental health and engineering at Johns Hopkins University.

"There is nothing magical about these variants. All the things that everyone knows how to do -- wearing masks, good ventilation, distance, etc. -- all these things are still effective," Gronvall said. "It is a bit of a race with vaccination, because these variants are more transmissible, which is blunting the effect of the vaccination."

According to Brownstein, it's possible that in the years ahead, specialized booster shots may offer even better protection against any new variants that emerge in the future.

"As we let viruses evolve, there may be variants that can evade current vaccines, which is where boosters will be helpful," Brownstein said.

Scientists are already testing booster shots. But so far, all evidence indicates that currently available vaccines protect against the B.1.1.7 like they protect against the others.

"I think we should see a booster in the U.S. in the next 1-2 years, but this will all come down to hospitalization and mortality data," Brownstein said. "We don't know yet if the booster will be based on B.1.1.7 or another variant."

Karine Tawagi, M.D., a hematology and oncology fellow at Ochsner Medical Center in New Orleans, is a contributor to the ABC News Medical Unit.