Moderna says bivalent vaccine appears to work against Omicron subvariants BA.4 and BA.5

An updated version of Moderna’s Covid-19 booster shot appears to work against the fast-spreading omicron subvariants BA.4 and BA.5, the company said in a news release Wednesday.

The bivalent vaccine, which Moderna has said it hopes will be authorized for use in the United States this fall, is designed to target both the original omicron variant and the original coronavirus strain in a single shot.

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Late-stage clinical trial results found the updated shot elicited about a fivefold increase in antibodies against BA.4 and BA.5 in previously vaccinated and infected individuals, according to the company.

However, the shot did not generate as many antibodies as it did against the original omicron variant, the company said, eliciting antibodies against the two subvariants that were about threefold lower.

Moderna said the findings add to results shared earlier this month, which found a 50 microgram dose of the updated shot — the same dosage given in the current booster shot — appeared to provide strong protection against the omicron variant.

Moderna's findings were announced in a news release, and the full data has not yet been made available for outside scientists to scrutinize.

BA.4 and BA.5 have been steadily gaining ground in the U.S., and experts worry about the subvariants' ability to dodge immunity and cause more reinfections. There are concerns that they may also cause more severe illness.

Dr. William Schaffner, an infectious diseases expert at the Vanderbilt University Medical Center, called Moderna's trial results "good news," saying the updated shot should provide protection against BA.4 and BA.5, which are expected to be the dominant strains in the country by the end of summer.

Schaffner noted that experts had been unsure whether the shot, designed to target the original variant, would work against BA.4 and BA.5. The two subvariants make up about 35% of all new Covid cases, according to data from the Centers for Disease Control and Prevention.

BA.4 and BA.5 share many similarities to the original variant, he said, but also appear to have mutations that make them more transmissible.

John Moore, a professor of microbiology and immunology at Weill Cornell Medical College, remained doubtful that the bivalent vaccine would be a game changer against omicron and its growing family of subvariants.

He said he'd like to see additional data from Moderna that was not included in Wednesday's news release, including how the updated shot stacks up against Moderna's existing booster shot.

"To go to the trouble of rolling out a new vaccine, Moderna needs to show it's a better option," Moore said.

Bill Hanage, an associate professor of epidemiology at Harvard University’s T.H. Chan School of Public Health, said while the Moderna data appears "impressive," it's also unclear how long the protection from the bivalent shots will last.

A CDC study published in February found that antibodies generated from a booster dose of either the Moderna or Pfizer-BioNTech vaccine wane after about four months.

Moderna said Wednesday it will submit the data to the Food and Drug Administration as it prepares to potentially distribute doses of the updated shot in the U.S. in August.

On June 28, the FDA’s advisory committee is scheduled to meet to discuss what strain or strains should be included in Covid booster shots for the fall. Moderna is expected to present data on its bivalent vaccine during the meeting.

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