Moderna on Tuesday announced preliminary study results for an updated "bivalent booster" shot indicating it may provide improved protection against new Covid-19 variants.

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Moderna's 'bivalent booster' may offer greater protection

For the preliminary study, Moderna tested a bivalent booster shot, called mRNA-1273.211, which contains equal mRNA amounts of ancestral SARS-CoV-2 and spike proteins from the beta variant.

While mRNA-1273.211 does not contain vaccine that specifically targets the more recent delta or omicron variants, STAT News reports, it produced levels of antibodies that blocked all recent variants, including beta, delta, and omicron better than Moderna's existing Covid-19 vaccine.

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"We believe that these results validate our bivalent strategy, which we announced and began pursuing in February 2021," said Moderna CEO Stéphane Bancel.

According to STAT News, for each variant, a 50-microgram dose of the updated booster produces roughly twice the amount of neutralizing antibody levels compared with Moderna's existing booster dose.

"We believe that a bivalent booster vaccine, if authorized, would create a new tool as we continue to respond to emerging variants," Bancel added.

Although the preliminary study produced encouraging results, a preprint published alongside Moderna's press release underscored the study's limitations. "The study was not designed and randomized to compare different booster candidates or dose levels head-to-head and the evaluation of booster candidates was sequential and open-label," the authors wrote.

In addition, the study did not generate measures of neutralizing antibodies in the laboratory simultaneously—making it impossible to determine whether the antibody boost provided by mRNA-1273.211 prevents infection or severe illness better than the existing booster, STAT News reports.

Challenges surrounding annual boosters

In related news, experts earlier this month at a hearing of an FDA advisory panel discussed how governments should make decisions about the composition of annual boosters. Many were adamant that governments should determine the composition of annual shots instead of pharmaceutical companies, STAT News reports.

Experts at the hearing also voiced concern over the biggest problem surrounding annual influenza shots—people often don't get them, a trend that has extended to the current Covid-19 boosters. According to data presented to the FDA panel, 217 million Americans have received a Covid-19 vaccine, but only 90 million have received a booster shot.

Currently, Moderna is not planning on moving forward with this vaccine based on these data, STAT News reports. Instead, the company is conducting another study of its mRNA-1273.214 booster based on the omicron variant, with results expected in the second quarter.

Since that study appears to randomize volunteers to receive either the updated booster or the original, it should provide clearer data. According to Moderna's release, the company is hoping to "inform selection of its candidate for the Northern Hemisphere fall 2022 booster." (Herper, STAT News, 4/19; Doherty, Axios, 4/19)