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Pfizer says Booster Neutralized Omicron, but variant can avoid two doses




Pfizer Inc.

PFE -0.62%

and BioNTech SE BNTX -3.55%

said that a third dose of their Covid-19 vaccine neutralized the Omicron variant in laboratory tests, but that the two-dose regimen was significantly less effective at blocking the virus.

A third dose increased antibodies 25-fold compared to two doses of the Omicron variant, the companies said. Nevertheless, two doses may prove effective in preventing serious Covid-19 disease, they said, because immune cells are able to recognize 80% of the parts of the spike protein that the vaccine targets.

The results were published in a press release from the companies, and were not peer-reviewed and published in a scientific journal.

The findings from the companies̵[ads1]7; early study, and one of researchers in South Africa, suggest that three doses will be needed to produce a similar immune response to Omicron which was given by only two doses in previous strains of the virus.

It also strengthens the argument for repeated and periodic boosters to maintain people’s immune systems against a developing Covid-19, the companies said.

“This is very positive news that should make everyone even more motivated to get vaccinated,” said Pfizer Chief Scientific Officer Mikael Dolsten.

The companies’ current vaccine will provide a strong defense against Omicron, especially if people are given a booster injection, said Dr. Dolsten. The three-dose regimen, he added, could provide stop protection against Omicron through the winter and until a new vaccine aimed directly at the variant will be ready if necessary.

President Biden outlined U.S. plans to combat the Omicron variant on Thursday, which include expanded access to booster shots for all adults, a masked mandate for public transportation and stricter rules for international travelers. Photo: Mandel Ngan / Agence France-Presse / Getty Images

Pfizer and BioNTech are working on an Omicron-specific vaccine that they hope to have available by March 2022 if the variant becomes widespread by then. Researchers began working on the new vaccine on Thanksgiving Day, November 25, shortly after Omicron was identified.

The vaccine trains the immune system to fight the virus by generating immune system soldiers known as antibodies, which attach to the virus and prevent it from replicating in healthy cells. The vaccine also produces other immune system fighters called T cells that can strike after infection to help target and remove the virus, and prevent more serious illness.

Pfizer and BioNTech said that Omicron still appears to be susceptible to T cells produced by the vaccine.

Dr. Dolsten estimates that there is a greater than 50% chance that Omicron will be the dominant tribe that spreads in the United States by spring, although it is too early to know for sure, he said.

A clinic in Stamford, Conn., Administered Covid-19 vaccinations on Tuesday.


Photo:

Amir Hamja for The Wall Street Journal

Preliminary laboratory data come from an analysis of blood samples from vaccinated patients measuring antibodies capable of neutralizing the virus that causes Covid-19, including the Omicron variant. Blood samples were taken three weeks after patients received their second dose, or one month after receiving their third dose.

The number of antibodies generated by a third booster shot against Omicron is equal to two doses against an older strain of the virus, the companies said.

“These preliminary data appear to indicate that the Pfizer vaccine is in fact protecting against Omicron, and that is very good news,” said Philip Landrigan, director of Boston College’s Global Public Health and Global Common Good program.

Monica Gandhi, a professor of medicine at the University of California, San Francisco, said the results suggested that two doses would protect many people from getting serious cases leading to hospitalization or death.

“Two doses are still effective against serious illness, whether people get boosters or not,” said Dr. Gandhi, who recommends boosters for high-risk patients, including those with HIV. “For people at high risk for serious illness, it is so important to get them strengthened, but I do not think it is mandatory for young healthy people.”

The company’s early findings come the day after researchers in South Africa reported findings from early laboratory tests indicating a 41-fold reduction in the Pfizer-BioNTech vaccine’s neutralization of Omicron than the original version of the virus.

A line on Tuesday at a vaccination clinic in Stamford, Conn.


Photo:

Amir Hamja for The Wall Street Journal

However, the researchers found greater antibody response to Omicron in blood taken from subjects who had been fully vaccinated and had previously been infected with Covid-19.

The companies will continue to work with a variant vaccine despite the promising signs that boosting with the original shot provides good protection against Omicron, said BioNTech CEO Uğur Şahin. This is because they will need to see more data on how their vaccine holds up against the new variant, including real-world data, which is expected in the coming weeks.

“Only in combination will we understand the relevance of this data and potential protection against Omicron-mediated disease and serious illness,” he said.

Real data on vaccine efficacy against Omicron will not be available for at least six weeks, said Dr. Şahin, because the case numbers must be higher before this can be measured.

In the meantime, the companies continue to produce an Omicron-specific vaccine. The first doses, for experimental use, will be ready in January, BioNTech executives said.

Omicron was first identified by researchers in South Africa last month. Since then, the World Health Organization has considered it a variant of concern. And it has since been discovered all over the world, including in the United States

Researchers have tried to understand how contagious the new strain is, as well as how well it may be able to avoid Covid-19 vaccines and whether it causes serious illness. Some preliminary reports suggest that the variant is more contagious, but may cause milder disease, although researchers say it is too early to know.

Pfizer and BioNTech said they expect to make four billion vaccine doses next year, although an Omicron-specific vaccine is needed by then.

Dr. Dolsten said that no matter how widespread Omicron becomes, there will likely be a need for continued booster shots going forward to provide protection against Covid-19. A fourth booster dose will probably be needed in the spring or fall of 2022, he said.

“It is becoming increasingly clear that you need to have a long-term perspective, with continued reinforcement to have strong lasting immunity,” said Dr. Dolsten. “If the landscape looks like it does today, we will probably continue to increase with the current vaccine.”

Pfizer’s shares rose 1% while BioNTech’s US custodian shares fell 0.2% in morning trading.

Write to Joseph Walker at joseph.walker@wsj.com

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