Clinical trials for omicron-specific Covid-19 boosters are currently underway, but a new preprint study published Friday in bioRxiv suggests that Moderna's omicron-specific booster "may not provide greater immunity or protection" than its current Covid-19 vaccine.

Omicron-specific boosters may not provide increased protection

For the preprint study, which has not yet been peer reviewed, scientists at the National Institute of Allergy and Infectious Diseases' Vaccine Research Center compared the levels of protection against the omicron variant in primates that were given a dose of either Moderna's licensed Covid-19 vaccine or its omicron-specific booster.

The researchers found that primates boosted with Moderna's original vaccine and primates boosted with the omicron-specific dose had similar levels of protection from disease in their lungs. Further, an analysis of the animals' blood showed that several measurable immune responses, including neutralizing antibody levels, were not significantly different between either group.

"Therefore, an [o]micron boost may not provide greater immunity or protection compared to a boost with the current [Moderna] vaccine," the researchers concluded.

According to the study's senior author, Robert Seder, additional studies conducted in humans will be needed to further validate the findings. However, he noted that it currently doesn't seem necessary to update the vaccine strains. "From [Moderna's] standpoint, I don't know how they view this," he said. "But I think [this] data [is] fairly clear."

In an email, Moderna said it will continue to work to keep up with the virus, STAT News reports. "We believe protection against variants of concern will be important, especially as we look ahead to the fall of 2022," the company wrote. "We will continue to follow the science and epidemiology of SARS-CoV-2 and potential new variants of concern. We are committed to remaining ahead of the virus as it evolves."

Are omicron-specific boosters necessary?

Although an omicron-specific booster could help provide increased protection against current strains, many experts have argued that we don't yet know what future variants will look like. We could see variants that mirror omicron, the original SARS-CoV-2 strain, or something that doesn't resemble any existing variant at all, The Atlantic reports.

According to Rafi Ahmed, an immunologist at Emory University, future vaccine regimens should include omicron "for sure." However, he said they should also "include one of the earlier strains," while allowing for future variants as they arise.

Ideally, "we should be vaccinating with what's circulating," said Katie Gostic, an infectious-disease modeler at the University of Chicago. "That has the best chance of protecting you today."

However, John Moore, a virologist at Weill Cornell Medical College, said the preprint study's findings, along with earlier research on the beta-based booster, suggest the current Covid-19 vaccine is generating cross-protective responses.

"Accordingly, changing to an [o]micron boost may well be unnecessary—literally more trouble than it's worth," Moore said. He added that he expects Pfizer and Moderna's current human trials on omicron-specific boosters will show similar results. "What we have is likely to be important for formulating future policies."

Separately, Angela Rasmussen, a coronavirus virologist at the University of Saskatchewan's Vaccine and Infectious Disease Organization, agreed, while cautioning that the preprint study's findings were based on a small number of animals. "I think we'll have to wait for human trial results to see if there's a difference in the real world at population scale," she said.

Still, Rasmussen said she wasn't surprised by the results of the preprint study, saying they were consistent with the trends seen throughout the omicron wave.

"The existing boosters provide improved (but imperfect) protection against infection," she said. "Based on these data, it doesn't look like an [o]micron-specific booster would improve that all that much. Certainly both booster formulations provide significant protection compared to the controls, but it may not be necessary to have [o]micron-specific boosters." (Branswell, STAT News, 2/4; Wu, The Atlantic, 2/1)