The US Food and Drug Administration (FDA) has approved the first vaccine for respiratory syncytial virus (RSV), a respiratory virus that can be particularly dangerous for babies but can also endanger older adults. The vaccine, called Arexvy, was developed by GlaxoSmithKline (GSK) and is the first of several potential RSV vaccines in the pipeline to be licensed anywhere. The decision comes after decades of failure in the quest for an RSV vaccine and follows a virus surge last fall that strained hospitals.

RSV is a cold-like nuisance for most people but can be life-threatening for the very young, the elderly, and people with certain high-risk health problems. In the US, about 58,000 children younger than 5 are hospitalized for RSV each year, and several hundred die. Among older adults, as many as 177,000 are hospitalized with RSV, and up to 14,000 die annually.

GSK’s new vaccine for older adults trains the immune system to recognize a protein on RSV’s surface and contains an ingredient called an adjuvant to further rev up that immune reaction. In an international study of about 25,000 people aged 60 and older, one dose of the vaccine was nearly 83% effective at preventing RSV lung infections and reduced the risk of severe infections by 94%.

To see how long protection lasts, GSK is tracking study participants for three years, comparing some who get just one vaccination during that time and others given a yearly booster. Shot reactions were typical of vaccinations, such as muscle pain and fatigue.

The FDA is also considering competitor Pfizer’s similar vaccine for older adults. Pfizer is seeking approval to vaccinate pregnant women, so their babies are born with some of mom’s protection. There isn’t a vaccine for kids yet, but high-risk infants often get monthly doses of a protective drug during RSV season, and European regulators recently approved the first one-dose option. The FDA is also considering whether to approve Sanofi and AstraZeneca’s one-shot medicine.

The Centers for Disease Control and Prevention (CDC) must decide if every senior really needs RSV protection or only those considered at high risk from the respiratory syncytial virus. CDC’s advisers will debate that question in June. If the CDC ultimately recommends the vaccination for some or even all seniors, it will add another shot for the fall along with their yearly flu vaccine – and maybe another COVID-19 booster.

“This is a great first step … to protect older persons from serious RSV disease,” said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases, who wasn’t involved with its development. Next, “we’re going to be working our way down the age ladder” for what’s expected to be a string of new protections.

“This is a very exciting time with multiple potential RSV solutions coming out after years of really nothing,” said Dr. Phil Dormitzer, chief of vaccine research and development for GSK.

Why has it taken so long to come up with a vaccine? The field suffered a major setback in the 1960s when an experimental shot worsened infections in children. Scientists finally figured out a better way to develop these vaccines — although modern candidates still were first tested with adults.