Pfizer said on Monday its respiratory syncytial virus (RSV) vaccine Abrysvo generated a strong immune response in a late-stage study of four groups of adults aged 18 and older with a compromised immune system.

A single 120 microgram dose of the vaccine generated strong neutralizing antibodies against both subtypes of RSV, called RSV-A and RSV-B, across all groups in the study, Pfizer said.

Abrysvo was well-tolerated in the study and showed a safety profile consistent with findings from other studies of the vaccine, it added.

The drugmaker plans to submit the data to regulatory agencies for review.

The study tested two doses of Abrysvo in 203 adults across four groups – those with a type of lung cancer, end-stage kidney disease, autoimmune inflammatory disorder, and solid organ transplant recipients – all of whom have compromised immunity and are at risk of developing severe RSV-associated disease.

Pfizer’s vaccine is currently approved for people aged 60 and older and for use in women during the middle of the third trimester of pregnancy to protect their babies.

RSV typically causes cold-like symptoms but is also a leading cause of pneumonia in toddlers and older adults, leading to 177,000 hospitalizations and 14,000 deaths in the United States annually.