GSK aims to get its respiratory syncytial virus (RSV) vaccine to regulators for review later this year, after interim data showed the vaccine was effective in a keenly-watched late-stage study involving older adults.

RSV is a leading cause of pneumonia in toddlers and the elderly, but the complex molecular structure of the virus and safety concerns have stymied efforts to develop a vaccine since the virus was first discovered in 1956.

Companies including Pfizer, J&J, Sanofi, Moderna  and AstraZeneca, are also racing to get an RSV therapy or vaccine approved.

The latest GSK trial is the first to show statistically significant efficacy for RSV in adults aged 60 years and older, the British drugmaker said of the ongoing study on Friday.

The company’s shares were up about 2.4% in early trade.If approved, the RSV vaccine is expected to generate billions for GSK, which is already the world’s biggest vaccine maker by sales but has faced pressure from activist investors such as Elliott Managementwho have urged the London-based company to shore up its drug pipeline.

The RSV data is a critical boost to GSK’s drug development success rate as it prepares to spin off its consumer health venture next month into an independent listed company called Haleon. After the split, GSK will focus solely on vaccines and prescription drugs.

GSK is also evaluating whether the shot given to pregnant women can confer immunity to unborn children.

In February, the company stopped enrolment and vaccination in three RSV trials in pregnant women, after initially pausing the studies based on safety recommendations from an independent committee.

In the trial with older adults, GSK said that no unexpected safety concerns were observed in the interim analysis.

RSV is one of most common disease-causing viruses. The majority of cases are mild, but it causes about 360,000 hospitalisations and more than 24,000 deaths globally each year, according to GSK figures.

Swedish Orphan Biovitrum’s Synagis monthly treatment is currently the only preventive therapy against RSV in high-risk infants.

On Friday, GSK did not disclose the magnitude of protection conferred by the vaccine except to say that the vaccine offered “exceptional protection” for older adults from the serious consequences of RSV infection.

Instead, the details will be presented in medical journals and an upcoming scientific meeting.

Jefferies analysts predicted the vaccine for older adults could generate $2.5 billion in global peak sales in a note published last month.