The US Food and Drug Administration (FDA) has approved the first-ever vaccine for respiratory syncytial virus (RSV). The single-shot vaccine intended for use in adults aged 60 or older represents the culmination of six decades of research to protect the world from RSV.

With the green light from the FDA on Wednesday, GSK’s Arexvy vaccine could be available as early as this fall, officials said. The speed of the vaccine’s public rollout hinges on receiving the final stamp of approval from the US Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices, which will meet in June.

RSV is a virus that kills over 100,000 children under the age of five every year. While RSV’s cold-like symptoms are often viewed as non-threatening to adults, the virus kills around 14,000 adults in the United States every year and has an annual global death toll of 160,000 people.

“Today’s approval of the first RSV vaccine is an important public health achievement to a disease which can be life-threatening,” said Dr Peter Marks, who heads the Center for Biologics Evaluation and Research at the FDA.

The US FDA approval follows its review of the data from an ongoing randomized control trial of nearly 25,000 older adults. Results from the study published in the New England Journal of Medicine in February showed the GSK vaccine reduced the risk of developing lower respiratory tract disease, which is caused by the virus, by 83%. It also reduced the risk of contracting severe lower respiratory tract disorder by 94%.

Dr Len Friedland, director of scientific affairs and public health at GSK, acknowledged the occurrence of several serious adverse side-effects throughout the study, but said they were evenly split between the group that got the vaccine and the one that received the placebo. Researchers would continue to monitor the vaccine’s safety profile as the trial moves forward, he added.

The most common minor side effects observed in the participants were injection site pain, fatigue, muscle pain, headache and joint stiffness.

A battle since the 1960s

Scientists have been trying to figure out a way to combat RSV since the 1960s. Between 1966 and 1968, a promising clinical trial for an early RSV vaccine candidate went badly wrong, killing two young children involved in the trials. Many more children vaccinated as part of the study needed to be hospitalized, with some suffering from more severe forms of RSV as the vaccine backfired.

It wasn’t until years later that scientists discovered that the protein inside the RSV virus shifts between two shapes, similar to the coronavirus SARS-nCOV-2. The shape-shifting nature of the protein meant scientists were trying to hit a moving target. The protein eluded the aim of scientists until 2013 when researchers from the National Institutes of Health (NIH) found a way to freeze the protein in one of its two shapes, allowing the development of vaccines targeted at the now immobile protein.

While RSV has long been a regular virus in the winter seasons, it gained attention when thousands of young children and older adults began filling up hospitals during the summer seasons in 2021 and 2022.

In 2020, most of the world was still under the COVID-19-induced lockdown and following precautionary measures like using face masks and frequently washing hands. As those precautionary measures were lifted, vulnerable groups of people began contracting RSV and ending up in hospitals.

Other RSV vaccines in the queue

The US FDA is set to decide on another RSV vaccine by the end of May. This vaccine is also targeted at older adults and is manufactured by Pfizer. If approved by the FDA, Pfizer’s vaccine will be up for final approval for public use alongside the GSK vaccine when the CDC’s Advisory Committee on Immunization Practices meets in June.

Another vaccine by Pfizer is also awaiting approval from the FDA by the end of August. This vaccine targets infants susceptible to RSV and, if approved, will be administered to pregnant women.

Moderna and Bavarian Nordic are also currently in phase-3 of clinical trials for their RSV vaccine candidates for older adults.

Image Credits: NIAID.