Updated 5:00 p.m. ET
There's more mixed news about the power of vaccines to protect people against the omicron variant — this time about the Moderna vaccine.
A preliminary study made public Wednesday studied blood samples in the lab from 30 people who had gotten two Moderna shots, and it found that the antibodies in their blood are at least about 50 times less effective at neutralizing the omicron variant of the coronavirus.
Previous research had indicated the Pfizer-BioNTech vaccine is also less protective against omicron.
"The antibodies that people make after they get the standard two inoculations of the Moderna mRNA vaccine are 50 times less effective against omicron than they are against the original form of the virus," says David Montefiori, a virologist at Duke University who helped conduct the study.
But there was good news too. An additional 17 people in the study had received a Moderna booster. And the antibodies in their blood were highly effective at blocking the omicron variant — essentially about as effective as they are at blocking the delta variant, Montefiori says.
"What these results are telling us is that if omicron becomes a dominant variant, it's going to become even more important that people get their boost," Montefiori says.
That would especially be important for elderly people and people with health problems that put them at increased risk, he says.
These findings are similar to those of studies done in labs on the blood of people who had gotten the Pfizer vaccine. Those also showed that people's antibodies were markedly less potent against omicron.
The latest study, which has been released on a preprint server but has not yet been reviewed by other scientists, involved testing antibodies in the blood of vaccinated people against a "pseudovirus," which is a virus created in the lab to mimic the mutations found in the omicron variant.
Based on the findings, Montefiori says a new vaccine specifically targeting omicron probably won't be needed. During a White House briefing Wednesday, Dr. Anthony Fauci of the National Institutes of Health echoed that, both for the Pfizer and Moderna vaccines.
"Our booster vaccine regimens work against omicron. At this point, there is no need for a variant-specific booster," Fauci said.
Scientists are doing similar experiments testing the Johnson & Johnson vaccine alone, as well as the J&J vaccine with a Pfizer booster, and expect to have some results by early next week.
Public health experts are alarmed by the omicron variant because it has more mutations than any previous SARS-CoV-2 mutants and appears to be the most contagious variant yet.
Originally spotted in South Africa, the variant is now spreading quickly around the globe. It has already been detected in at least 33 U.S. states and appears to be spreading fast. The latest estimate from the Centers for Disease Control and Prevention is that omicron already accounts for about 3% of the samples the agency has analyzed, which is about a sevenfold jump from a week earlier.
The variant is already far more common than that in some parts of the country, such as in the New York and New Jersey area, where it's showing up in 13% of cases, according to the CDC.
Omicron spreads so fast that it's on track to overtake delta and become the dominant variant in the U.S. within weeks, raising fears it could accelerate the delta surge already underway.
"We could be facing very severe surges, very severe strains on our health care systems under the worst-case scenarios," says Lauren Ancel Meyers of the University of Texas at Austin, who has been modeling the possible impact of omicron on the United States.
"I'm worried," she says. "We don't want to be caught unprepared."
Data coming out of South Africa and the U.K. indicates that vaccinated people can still catch the omicron variant and can still end up in the hospital, but may not get as sick. But there are many questions about whether that would be the case in the U.S., where there aren't necessarily as many people who have added protection from natural exposure to the virus.
Nevertheless, the variant could still overwhelm the health system.
"While as a public health community we are still learning about the severity of cases caused by the omicron variant, modeling shows that even if it is less severe, the sheer number of cases that could come from a variant with the level of transmissibility that we are seeing in other countries could overrun our health care system resources, especially if it coincides with the current delta wave and flu season," says Adriane Casalotti of the National Association of County and City Health Officials.