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Omicron, Boosters and Vaccines News: Covid-19 Live Updates

ImageA nurse prepares Pfizer-BioNTech vaccines in McMinnville, Ore., in October.
A nurse prepares Pfizer-BioNTech vaccines in McMinnville, Ore., in October.Credit…Alisha Jucevic for The New York Times

Pfizer and BioNTech said Wednesday that laboratory tests suggest that three doses of their coronavirus vaccine offer significant protection against the fast-spreading Omicron variant of the virus.

The companies said that tests of blood from people who received only two doses found much lower antibody levels against the Omicron variant compared with an earlier version of the virus. That finding indicates that two doses alone “may not be sufficient to protect against infection” by the new variant, the companies said.

But the blood samples obtained from people one month after they had received a booster shot showed neutralizing antibodies against the Omicron variant comparable to those against previous variants after two doses, the companies said in a statement.

These experiments, done with blood samples in the lab, cannot say for sure how the vaccines will perform in the real world. Vaccines stimulate a wide-ranging immune response that involves more than just antibodies. So the experiments offer an incomplete picture of how well the vaccine will protect against severe outcomes from Omicron.

Still, the results seemed to underscore the importance of booster shots in combating infection from the new variant. “Our preliminary, first data set indicate that a third dose could still offer a sufficient level of protection from disease of any severity caused by the Omicron variant,” said Dr. Ugur Sahin, the chief executive officer of BioNTech, Pfizer’s German partner.

The companies suggested that Omicron would not significantly diminish the power of T cells — another, more lasting part of the immune system’s response to the coronavirus. Researchers identified parts of the Omicron variant that can be recognized by the T cells produced after vaccination. Most did not contain any mutations.

Pfizer did not present data showing how T cells actually perform against the variant. Nevertheless, the companies said that “vaccinated individuals may still be protected against severe forms of the disease” after only two doses.

“I would like to sound a note of reassurance,” said Dr. Paul Offit, a vaccine expert with Children’s Hospital of Philadelphia and a member of the Food and Drug Administration’s vaccine advisory committee. “In all likelihood, two doses of an mRNA vaccine will protect you against serious illness.”

“The virus has mutated to the point that it has become less neutralizable by antibodies,” he said. But he said there is no evidence that the vaccines have become less effective at preventing severe disease; protection comes not just from neutralizing antibodies, but from another arm of the immune system involving B cells and T cells.

Dr. Albert Bourla, the chairman and chief executive officer of Pfizer, said while two doses may still prevent severe disease from Omicron, “it’s clear from these preliminary data that protection is improved with a third dose of our vaccine.”

Dr. Peter Hotez, a vaccine expert with the Baylor College of Medicine, called the results “really good news.” But he noted that Pfizer’s experiments only measured the levels of neutralizing antibodies one month after the third shot, saying he was concerned by other research suggesting that those levels might drop off later, more sharply than expected..

The results come one day after a preliminary report on laboratory experiments in South Africa also found Omicron seemed to dull the power of two doses of Pfizer’s vaccine. The South African experiments did not try to evaluate how well three doses worked.

The Omicron variant has now spread to dozens of countries, and while the Delta variant is still overwhelmingly dominant in the United States, the Biden administration is bracing for a new flood of cases from Omicron.

At a White House briefing Tuesday, Dr. Anthony S. Fauci, the government’s top infectious disease expert, said it would still be weeks before scientists understand how virulent the Omicron variant is.

“We shouldn’t be making any definitive conclusions, certainly not before the next couple of weeks,” he said.

He said early reports from South African medical officials presented a somewhat hopeful picture of Omicron’s impact. Researchers at a major hospital complex in Pretoria reported this week that patients with the coronavirus are significantly less ill than those they have treated before, and that other hospitals are seeing the same trends.

“We are not seeing a very severe profile of disease,” Dr. Fauci said, adding that hospital stays were shorter and patients required less oxygen. “It might be, and I underscore might, be less severe, as shown by the ratio of hospitalizations per number of new cases.”

But he noted that South Africa’s population differed from that of the United States, with a high proportion of young people infected, a low percentage of people vaccinated, and a high rate of H.I.V., which can damage the immune system.

“With all the variants, there were always a lot of rumors flying about the differences in clinical illness,” Dr. Hotez said. “Maybe Omicron really is different. But I wouldn’t count on it just based on the anecdotes from South Africa.”

In an interview last week, Dr. Bourla of Pfizer said the company began developing a version of its vaccine specifically targeting Omicron right after Thanksgiving and could produce it in mass quantities within 95 days. Moderna is on the same path.

“We will be able to switch overnight production,” he said. “There’s not going to be a need to start producing new machinery, new equipment, new formulations.”

But he also noted that Pfizer developed two other prototypes in response to new variants, and neither proved necessary because the original vaccine worked against the virus’s mutations.

He said that while lab results are a good indicator of what comes next, it will take a month or two to get real-world data from countries like Israel that carefully track every patient. That will show whether people who got three shots of Pfizer’s vaccine are experiencing breakthrough infections or whether those infections are mostly among the unvaccinated, he said.

The South African study published Tuesday found that antibodies produced by people with two doses of vaccine were much less successful at keeping the Omicron variant from infecting cells than other forms of the coronavirus.

That data suggests that vaccinated people might be vulnerable to breakthrough infections with Omicron, but offered fewer clues of how well the vaccine protects against more severe outcomes from the variant.

Noah Weiland and Carl Zimmer contributed reporting.

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