COVID-19 booster shot may be effective against omicron BA.2 variant, study shows

New evidence shows a booster dose of the coronavirus vaccine may provide protection against a subvariant of omicron – the variant which has rapidly become the dominant strain in the world and currently accounts for most cases of the virus in the U.S.

Researchers from Beth Israel Deaconess Medical Center examined neutralizing antibodies produced after vaccination or infection. These are antibodies that can bind to the virus and block its entry into cells.

The study, funded in part by the National Institutes of Health’s National Cancer Institute and published in the New England Journal of Medicine, found that after a booster vaccination, levels of antibodies in the blood that could bind to and neutralize a new omicron variant increased substantially. 

The team tested antibodies from the blood of 24 people who had been vaccinated and boosted with the Pfizer shot. In addition, they looked at antibodies from eight people who had recovered from COVID-19, seven of whom had also been vaccinated.

The omicron variant has three major sublineages: BA.1, BA.2, and BA.3. BA.1 rapidly became dominant, and the number of cases of BA.2 has recently increased in many regions of the world.


Medical center holds COVID-19 vaccine before it is administered in a clinical trial. (Michael Ciaglo/Getty Images)

"Our data show that a boost of the Pfizer vaccine is needed for the generation of neutralizing antibodies against the BA2 variant. Antibodies against BA2 are similar to Omicron BA1, but both are lower than against the original Wuhan strain," Dr. Dan Barouch, the team’s lead researcher, told FOX Television Stations. 

The NIH echoed Barouch’s remarks in a press release writing, "After the booster dose, levels of antibodies that could neutralize BA.2 jumped substantially. The number that could recognize BA.2—as well as BA.1—after the booster dose was higher than those recognizing the original virus after only the first two shots."

According to the study, the number of antibodies that could recognize BA.2 was even higher in people who had been vaccinated and infected with the original omicron variant. The one person who had no detectible neutralizing antibodies in their blood after exposure to COVID-19 hadn’t been vaccinated.

Barouch continued, "These results indicate that the recent increase in COVID-19 cases caused by BA.2 is more likely due to an improved ability of the virus to spread from person to person rather than its ability to evade the immune system."

Limitations from this study include it being a small laboratory study, which didn't measure actual clinical effectiveness, Barouch added. 

About half of Americans have received booster shot

About half of eligible Americans have received booster shots, and there have been nearly 80 million confirmed infections overall and many more infections have never been reported. 

One study from earlier this year used those factors and others to estimate that 73% of Americans were, at the time, immune to omicron.

RELATED: Influential model finds 73% of US now immune to omicron

According to health experts, this could prevent or shorten new illnesses in protected people and reduce the amount of the virus circulating overall, likely tamping down new waves.

"We have changed," said Ali Mokdad, a professor of health metrics sciences at the University of Washington in Seattle. "We have been exposed to this virus and we know how to deal with it."

But is omicron leading us closer to herd immunity against COVID-19?

Experts say it's not likely that the highly transmissible variant — or any other variant — will lead to herd immunity."

Herd immunity is an "elusive concept and doesn’t apply to coronavirus," said Dr. Don Milton at the University of Maryland School of Public Health.

RELATED: Is omicron leading us closer to herd immunity against COVID-19? Experts weigh in

Herd immunity is when enough of a population is immune to a virus that it’s hard for the germ to spread to those who aren’t protected by vaccination or a prior infection.

Instead, populations are moving toward "herd resistance," where infections will continue, but people have enough protection that future spikes won't be as disruptive to society, Milton says.

Many scientists believe COVID-19 will eventually become like the flu and cause seasonal outbreaks but not huge surges.

What is the omicron variant?

The omicron variant was first discovered by scientists in South Africa in November 2021.

It appears to have a high number of mutations in the coronavirus’ spike protein, which affects how it can easily spread to people.

In February, the U.S. death toll from COVID-19 hit 900,000, less than two months after eclipsing 800,000, propelled in part by the wildly contagious omicron variant. 

RELATED: US COVID-19 death toll hits 900,000, sped by omicron

The two-year total, as compiled by Johns Hopkins University, was greater than the population of Indianapolis, San Francisco, or Charlotte, North Carolina.

President Joe Biden lamented the milestone, saying, "After nearly two years, I know that the emotional, physical, and psychological weight of this pandemic has been incredibly difficult to bear."

He again urged Americans to get vaccinations and booster shots. "Two hundred and fifty million Americans have stepped up to protect themselves, their families, and their communities by getting at least one shot — and we have saved more than one million American lives as a result," Biden said.

Currently, 75.6% of adults in the U.S. are fully vaccinated, or about 195 million Americans, according to the Centers for Disease Control and Prevention. 98.4 million people have received a booster dose of the vaccine.

The Associated Press contributed to this story.