'Our best defense': Pfizer says third dose of its COVID vaccine protects against omicron, Fauci expects same from Moderna's

A third dose of the Pfizer-BioNTech COVID-19 vaccine appears to be as effective against omicron as two doses were against the original variant, according to preliminary data from BioNTech.

The same study showed that two doses may prevent severe disease, but aren't nearly as effective against omicron as they were against earlier variants.

"The first line of defense with two doses of vaccination might be compromised (by omicron), and three doses of vaccination are required to restore protection," Özlem Türeci, BioNTech's chief medical officer, said at a Wednesday news conference.

In case it becomes necessary, BioNTech and its partner Pfizer are developing an omicron-specific vaccine, which should be ready for mass production in March if regulators sign off, BioNTech CEO Uğur Şahin said.

People should not wait for that targeted vaccine, he said, but should get a booster dose as soon as recommended. The Centers for Disease Control and Prevention has already encouraged everyone over 18 who was vaccinated more than two months ago with the Johnson & Johnson vaccine or more than six months ago with the Pfizer-BioNTech or Moderna vaccines to get a booster.

"The third dose has really an absolute added value," Sahin said. "It prevents not only infection and any type of disease, but it also increases the protection against severe disease."

Studies have not yet been completed on the effectiveness of the Moderna or J&J vaccines or their boosters against omicron. "Many people are asking that question," said Dr. Rebecca Weintraub, a global health expert at Brigham and Women's Hospital and Harvard Medical School, both in Boston. "We'll just have to wait a bit of time."

Moderna's vaccine is based on the same technology as Pfizer-BioNTech's, so presidential advisor Dr. Anthony Fauci told MSNBC Wednesday that he would be "very surprised" if the two vaccines weren't equally protective. "“Virtually everything we said about effectiveness of the Pfizer can be applied to Moderna," he said.

Although preliminary, Pfizer-BioNTech's study results were generally seen as positive, countering fears that mutations in the omicron variant would undermine vaccine effectiveness.

"It's encouraging results," said Kena Swanson, Pfizer's vice president, viral vaccines. "This is step one."

"I agree that our best defense NOW is a booster," Dr. Gregory Poland, director of the Mayo Clinic's Vaccine Research Group, wrote in an email.

"This along with three studies from academic labs presented yesterday provides reassurance that booster shots can achieve solid vaccine effectiveness against omicron, but we don’t know how durable that will be," said Dr. Eric Topol, director of the Scripps Research Translational Institute in California.

Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, said he's not yet convinced that a third dose is necessary. Two doses still likely prevent severe disease, he said, and unless people are prepared to get shots every few months, there's no way – or need – to prevent all infections with COVID-19.

The omicron variant has been spreading incredibly quickly in South Africa. It has been found in more than 50 countries and "here in the U.S., there are confirmed cases in 19 states, and we expect that number to continue to increase," CDC Director Dr. Rochelle Walensky said at a Tuesday White House press briefing.

Omicron appears to spread more easily than the delta variant, which has dominated the world since this summer.

First identified in both South Africa and Botswana the day before Thanksgiving, it's not yet clear whether omicron causes less severe disease than its predecessors. But if it is more contagious and sickens more people, more are likely to be hospitalized and die, regardless of how dangerous the variant is.

Omicron had raised concerns because it has more than 50 genetic differences compared with the original virus, many on the so-called spike protein that is the target of most COVID-19 vaccines and monoclonal antibody therapies.

The Pfizer-BioNTech study is the first to show that vaccines retain some of their effectiveness against the omicron variant. Other vaccine makers have not yet made public studies of their effectiveness against omicron.

The new research looked at blood samples from nearly 20 people who received a second dose of the Pfizer-BioNTech vaccine three weeks earlier or a third dose a month earlier. They looked for antibodies in the blood that could counter a manufactured version of the virus.

Samples of people who received three doses had high levels of antibodies that neutralize the omicron variant, while people who received only two doses lacked those antibodies.

Because the spike protein remains largely unchanged, Türeci said, "we expect that two doses of our vaccine may still induce protection against severe disease with omicron."

In addition to waiting for real-world studies of the vaccine's effectiveness against omicron, the company is also testing antibodies against live virus samples in a secure lab, as well as examining samples from people who received their shots longer ago, as well as children, Sahin said.

Whether an omicron-specific vaccine is needed will depend on whether the new variant continues to advance around the world and how protection from the original vaccine holds up – information that should be available before March.

It's too soon to know whether more than three doses will be needed to protect against COVID-19 going forward or whether immunocompromised people, who have been encouraged since the fall to get a third dose, would benefit from a fourth dose now.

Data is not yet available, but researchers are concerned that monoclonal antibodies, which have been used to protect high-risk people from developing severe disease when infected, will lose their effectiveness in the face of omicron. Antiviral drugs made by Merck and Pfizer should continue to work, experts say, but studies have not yet been completed to prove that.

Scientists said they were hopeful, but lobbied for patience, saying solid scientific research takes time to answer questions about a new variant.

"It's early days. I'm guardedly optimistic with a good dose of realism and patience for more in-depth (research)," said Dr. Barton Haynes, an immunologist at Duke University Medical Center

Swanson agreed.

"We all have the same questions," she said.

Contact Karen Weintraub at kweintraub@usatoday.com.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID-19: Pfizer says 3rd dose of its vaccine protects against omicron