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Covid-19

Covid-19 News: Live Updates – The New York Times

Credit…James Estrin/The New York Times

A report from South Africa offered a first look at how vaccinated people might fare against the rapidly spreading Omicron variant of the coronavirus.

Lab experiments showed that Omicron appears to be attenuating the potency of the Pfizer-BioNTech vaccine, but also hinted that people who received a booster shot may be better protected.

The study, published online Tuesday, found that antibodies produced by vaccinated people were far less successful in preventing the Omicron variant from infecting cells than other forms of the coronavirus.

Scientists said the results were somewhat concerning, but no cause for alarm. The data suggests that vaccinated people may be vulnerable to breakthrough infections with Omicron, which is spreading rapidly in South Africa and has appeared in dozens of countries around the world.

But vaccines stimulate a broad immune response that involves more than just antibodies. Thus, these experiments provide an incomplete picture of how well the vaccine protects against hospitalization or death from Omicron.

“While I think there will be a lot of infections, I’m not sure if this will translate into systems collapse,” Alex Sigal, a virologist at the Africa Health Research Institute in Durban, South Africa, who led the study, said in an interview. “My guess is it will be under control.”

dr. Sigal and his colleagues have been working at breakneck speed for the past two weeks growing the virus and then testing antibodies against it. “If I don’t die from the virus, I die of exhaustion,” he said.

Originally, Dr. Sigal that vaccines might not protect at all. It was possible that the Omicron variant had developed a new way to enter cells, which would have rendered antibodies from vaccines useless. “Then all our efforts would be waste,” he said.

Fortunately, that turned out not to be the case.

dr. Sigal and his colleagues used antibodies from six people who received the Pfizer vaccine without ever having had Covid-19. They also analyzed antibodies from six other people who were infected before receiving the Pfizer vaccine.

The researchers found that all volunteers’ antibodies performed worse against Omicron than against an earlier version of the coronavirus. Overall, the potency of their antibodies to Omicron dropped dramatically, to about one fortieth the level seen when tested with an earlier version of the virus. That low level of antibodies may not protect against breakthrough Omicron infections.

Theodora Hatziioannou, a virologist at Rockefeller University who was not involved in the study, said that number was not surprising. “It’s more or less what we expected,” she said.

The results may help explain some high-profile superspreading events caused by Omicron. At an office Christmas party in Norway, the virus appears to have infected at least half of the 120 vaccinated attendees.

dr. sigal announced the results on Twitter on Tuesday afternoon.

His team found a clear difference between the two groups of volunteers. The antibodies of the six uninfected vaccinated people were very weak against Omicron. But among the volunteers who had Covid-19 before the vaccination, five out of six still gave quite strong responses.

One reason for the difference is that people who are vaccinated after an infection produce more antibodies than people who are not infected.

dr. Sigal said the experiments can’t say much about how well boosters protect against Omicron until researchers test antibodies directly from people who have been given them. But he suspected that the increased level of antibodies would offer good protection. “The more you have, the better you’ll be,” he said.

Kristian Andersen, an infectious disease researcher at the Scripps Research Institute in La Jolla, Calif., who was not involved in the new study, agreed that booster shots would likely help ward off the new variant.

“I expect boosters to restore better levels of protection,” he said. “And, importantly, early clinical data from South Africa suggests that immunity – whether from vaccines or previous infections – is still effective in preventing the more severe forms of Covid-19.”

dr. Hatziioannou was less sure about boosters. She and her colleagues are conducting experiments with antibodies from boosters to test whether they will provide the same robust protection as in people who received vaccines after infection. “I want to say yes, but we have to wait,” she said.

Pfizer and Moderna said they were testing their vaccines against Omicron and could produce variant-specific vaccines in about three months.

Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, said the study reinforced the need to accelerate the development of Omicron-specific shots. While there remains some uncertainty about how widely the variant will spread, he said, the best way to restore protection against Omicron is to give people a vaccine that contains Omicron’s genetic information.

“Given the very large drop in neutralizing antibody titres seen here at Omicron,” he said, “it would certainly be worthwhile, in my opinion, to continue making Omicron-specific vaccines as soon as it seems possible.” as if there was a possibility that it could spread widely.”