Moderna’s experimental COVID-19 vaccine that combines its original shot with protection against the omicron variant appears to work, the company announced today.

COVID-19 vaccine makers are studying updated boosters that might be offered in the fall to better protect people against future coronavirus surges.

Moderna’s preliminary study results show people given the combination shot experienced a higher boost in omicron-fighting antibodies than if they just got a fourth dose of the original vaccine.

“We believe strongly that this data supports an update of the vaccine,” Dr. Stephen Hoge, Moderna’s president, said today.

Today’s COVID-19 vaccines all are based on the original version of the coronavirus. They’re still providing strong protection against severe disease, hospitalization and death even after the appearance of the super-contagious omicron variant — especially if people have had an initial booster dose.

But the virus continues to mutate rapidly in ways that let it evade some of the vaccines’ protections and cause milder infections.

So U.S. regulators, and the World Health Organization, are considering whether to order a change in the vaccine recipe for a new round of booster shots in the fall — when cold weather and kids returning to school are expected to drive yet another surge.

Key questions: How to make that change without losing the continued strong protection against COVID-19’s worst outcomes? And what’s the right variant to target? After the huge winter omicron surge, that mutant’s genetically distinct relatives now are the main threats, including one that’s fueling the current U.S. wave of infections.

The Food and Drug Administration has set a meeting in late June for its scientific advisers to debate those questions and evaluate data from vaccine makers’ tests of potential new formulas. Pfizer also is studying a combination shot, what scientists call a bivalent vaccine, with some data expected later this month.

Moderna’s new study tested people who’d had three prior vaccinations, giving 377 of them a fourth dose of the original vaccine and another 437 the combo shot.

The study wasn’t designed to track how well the updated booster prevented COVID-19 cases and it was tested only against omicron, not the variants dominant now. But the bivalent vaccine sparked a nearly eight-fold rise in levels of antibodies capable of fighting omicron. Importantly, that was 1.75 times better than the antibody jump from simply giving a fourth dose of the original vaccine, Moderna said.

The data hasn’t undergone scientific review, and these initial measurements were taken a month after booster shots. Antibodies naturally wane so it’s not clear how long that protection could last. Moderna plans to track the levels at three and six months but already is manufacturing doses to be ready if regulators in the U.S. or elsewhere order a change for fall shots.