Moderna said its two new Covid-19 boosters boosted immunity against the main Omicron variant, boosting the company’s hopes of launching it as a fourth dose in late summer.

The U.S. biotech was the first to report preliminary results from a clinical trial of a vaccine against Omicron. It said Wednesday that trials showed the “bivalent enhancer” — which contains the genetic code of the Omicron variant and the original strain of the virus — was safe and well-tolerated.

When administered as part of a four-dose regimen, Moderna’s bivalent booster elicited an eight-fold increase in antibodies against the Omicron variant compared to pre-boost levels. It produced 1.75 times more antibodies than people who received a booster shot of Moderna’s existing vaccine.

Moderna added that the booster was responsive to both the original strain of the virus and its predecessors, and the vaccine candidate should provide longer-lasting protection against variants of interest.

On a conference call with investors, Moderna President Stephen Hoge said the new data showed the bivalent booster was “significantly better” in terms of the neutralization protection it provided for Omicron and that it was “clearly time” to update the vaccine .

Moderna shares were up more than 7 percent at $152.51 in early trade, while the Nasdaq Composite gained 0.3 percent.

Moderna’s UK general manager Darius Hughes said the company was “very, very pleased” with the results, which suggested the new vaccine would “provide better protection for the fall and winter booster”.

Many governments have yet to decide who should get the fourth dose in the fall and whether to offer a booster for Omicron. The United States and the United Kingdom have already delivered a fourth dose of the vaccine to some of the most vulnerable people, including the elderly. In April, EU regulators said it was too early to recommend a fourth dose of the vaccine for the general population.

Hughes said there was “some interest” in the UK to move to a vaccine more suitable for Omicron, which the country could do within the terms of its existing contract with Moderna.

If the bivalent vaccine is approved, Moderna will need to scale up production, moving from producing the original vaccine to manufacturing. Hughes said making the switch was an “interesting challenge” but the company had expanded its manufacturing operations around the world so it could move “very soon”.

Experts remain divided on whether annual boosters are needed for the new coronavirus variant, with some noting that existing vaccines continue to provide strong protection against severe illness and hospitalization.

However, others say a new booster may boost immunity to a variant of Omicron that continues to spread rapidly around the world.

“I would be cautiously optimistic that this bivalent vaccine will be at least more effective against Omicron than the original vaccine, but it’s too early to talk about it being a game-changer,” said David, an epidemiologist at the institute. Dowdy said. Johns Hopkins School of Public Health.

Pfizer is also advancing plans to develop an Omicron-specific booster that could better protect against new variants, but it acknowledges growing public fatigue with the vaccine.

Advisors to the U.S. Food and Drug Administration plan to discuss at a June 28 meeting whether current Covid vaccines should be modified and which strain of the virus they should target.

This article has been revised to reflect the increased immunity provided by boosters.