For weeks, New Yorkers have been witnessing the alarming rise of a native variant of the coronavirus that has stubbornly kept the number of cases in the city high. City officials have repeatedly warned that the variant could be more contagious and evade the immune response.

At least on this second point, they can now breathe easier: Both the Pfizer BioNTech and Moderna vaccines will be effective in preventing serious illness and death of the variant, according to two independent studies.

Antibodies stimulated by these vaccines are only slightly less effective in controlling the variant than the original form of the virus, both studies found.

“We don’t see any big differences,” said Michel Nussenzweig, an immunologist at Rockefeller University in New York and a member of the team that published one of the studies on Thursday.

The final result? “Get vaccinated,” he said.

The results are based on laboratory experiments with blood samples from a few vaccinated people and have not yet been assessed by experts. Still, they are consistent with what is known about similar variants, several experts said, and they complement a growing body of research suggesting that the two main vaccines in the United States protect against all of the variants identified so far.

“The takeaway message is that the vaccines against the New York variant and the South African variant as well as the British variant will work,” said Nathan Landau, a virologist at NYU’s Grossman School of Medicine who led the study.

The vaccines spur the body to build an expansive immune response using thousands of types of antibodies and different types of immune cells. A subset of these immune fighters, called neutralizing antibodies, is essential to preventing infection. But even when neutralizing antibodies are in short supply or even absent, the rest of the immune system can deploy enough defenses to fight off serious illness and death.

In both new studies, neutralizing antibodies from people who were vaccinated were able to thwart the virus better than those from people who developed antibodies because they had Covid-19. A head-to-head comparison of the two sets of antibodies offered a possible explanation: Antibodies from vaccinated individuals are spread over a wider range of parts of the virus, so no single mutation has a major impact on their effectiveness – vaccines are therefore a better choice against variants than immunity from natural ones Infections.

The variant first identified in New York, known to scientists as the B.1.526, sped through the city after its first discovery in November. By April 13, it was one in four diagnosed cases, and as of April 13, almost half of the cases. Variant B.1.1.7, which brought Great Britain to a standstill, is also widespread in New York. Together, the two account for more than 70 percent of coronavirus cases in the city.

Concern for the variant identified in New York has centered on a form that contains a mutation that scientists call Eek. The Eek mutation subtly changes the shape of the virus, making it difficult for antibodies to target the virus and, as a result, underperforms vaccines.

Updated

April 22, 2021, 8:45 p.m. ET

In the second study, Dr. Landau states that the Pfizer and Moderna vaccines are only marginally less protective against the variant that devastated the UK and against forms of the variant discovered in New York that do not contain the Eek mutation.

Several laboratory studies have shown that antibodies induced by the Pfizer and Moderna vaccines are slightly less effective against a third variant identified in South Africa that also contains Eek. Other vaccines fared worse. South Africa suspended use of the AstraZeneca vaccine after clinical studies showed that the vaccine did not prevent mild or moderate disease of the variant circulating there.

“It already started at a lower level in terms of the immunity it produced,” said Dr. Nut branch about the AstraZeneca vaccine. Regarding the Pfizer and Moderna recordings, he said, “We are so lucky in this country to have these vaccines compared to the rest of the world.”

Florian Krammer, an immunologist at the Icahn School of Medicine on Mount Sinai who was not involved in any of the new studies, said he was more concerned about other countries’ vaccination programs than the variants themselves.

“I’m less worried about variants than I was two months ago,” he said, but added, “I’m worried about countries that don’t have enough vaccines and that don’t have this vaccine launch.” In all honesty, I don’t worry about the US anymore. “

Dr. Landau also tested monoclonal antibodies used to treat Covid-19 against the variants. They found that the cocktail of monoclonal antibodies made by Regeneron was effective against both the variant discovered in New York and the original virus.

The studies are reassuring, but they show that the Eek mutation is being observed, said Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle.

“This could certainly be a step towards making the virus a little more resistant to infection- and vaccine-mediated immunity,” said Dr. Bloom. “I don’t think it’s something people need to be alerted about right away, but it definitely impresses us as important.”

Dr. Bloom led the analysis comparing vaccine-induced antibodies with those produced by natural infections. He found that the strongest antibodies bind to multiple sites in a key part of the virus. Even if a mutation affected binding at one site in that region, antibodies targeting the remaining sites would still be protective.

Antibodies induced by the vaccine cover many more sites in this region than those due to natural infection – and are therefore less likely to be affected by a mutation in any one site.

The study only looked at antibodies stimulated by the Moderna vaccine, but the results for the Pfizer BioNTech vaccine are likely to be the same, he added.

“This could potentially be a good thing as the virus creates mutations,” said Dr. Bloom.