Moderna on Wednesday said its experimental mRNA-based flu vaccine produced a stronger immune response against four strains of the virus than a currently available flu vaccine in a late-stage trial, clearing the way for a path to approval in the U.S. 

Shares of Moderna rose 4% in premarket trading Wednesday following the announcement.

The results come as Moderna tries to beef up its pipeline and become a company known for more than its blockbuster mRNA Covid vaccine, which won more approvals from U.S. regulators this week. Moderna expects its Covid shot – its only commercially available product – along with its flu jab, and other experimental respiratory vaccines to make up to $15 billion in sales by 2027.

Wednesday’s results are also a sigh of relief for Moderna after the company pushed back its experimental flu shot program in April. An initial vaccine formula didn’t accumulate enough data to determine its efficacy, so the company reformulated the shot. 

That appeared to pay off in the latest phase three trial. Moderna compared the flu vaccine, dubbed mRNA-1010, to a currently approved seasonal flu vaccine from GlaxoSmithKline called Fluarix. 

An interim analysis of the trial found that mRNA-1010 produced higher antibody levels for all four influenza strains recommended by the World Health Organization – two each for influenza A and B – compared to Fluarix. Moderna’s flu shot also generated higher seroconversion rates, which refers to the development of specific antibodies against a virus.

Moderna said the safety findings were similar in the trial to previous ones, which found muscle pain, headache, fatigue, pain and swelling as the most common side effects of mRNA-1010. 

Also on Wednesday, Moderna said it is ending a separate phase three trial on the first version of its flu vaccine. That study did not generate enough cases to provide efficacy data. 

Meanwhile, Moderna on Wednesday said it expects a decision from the Food and Drug Administration on its mRNA vaccine for respiratory syncytial virus in adults 60 and older by April. The FDA approved RSV vaccines for older adults from Pfizer and GSK in May. 

“Our mRNA platform is working,” Moderna CEO Stephane Bancel said in a press release. “With today’s positive phase 3 flu results, along with previous results in Covid and RSV, we are now three for three on advancing respiratory disease programs to positive phase 3 data.”

The company will hold a virtual event at 1 p.m. ET on Wednesday to discuss research and development updates with investors.