First vaccine targeting RSV wins FDA approval. More are coming.

U.S. regulators Wednesday approved the first vaccine to prevent the respiratory ailment RSV, a decision that marks a turning point in the six-decade-long quest to protect vulnerable people against the virus.

A shot developed by pharmaceutical giant GSK to protect older adults against the respiratory syncytial virus is the first to get a greenlight from the Food and Drug Administration. A Pfizer vaccine is following close behind and is under consideration for older adults and for pregnant people as a maternal vaccination that would protect newborn children. A monoclonal antibody treatment for babies, developed by Sanofi and AstraZeneca to offer vaccine-like protection during the winter RSV season, is also under consideration.

The progress arrives at a rare time of public awareness about the wintertime respiratory disease, after last year’s terrible RSV season crushed children’s hospitals across the country. For most healthy people, RSV is just another seasonal cold, but each year in the United States it fills pediatric intensive care units with babies gasping for air and sends more than 60,000 older adults to the hospital.

“Older adults, in particular those with underlying health conditions, such as heart or lung disease or weakened immune systems, are at high risk for severe disease caused by RSV,” Peter Marks, the director of the FDA’s Center for Biologics Evaluation and Research, said in a statement. “Today’s approval of the first RSV vaccine is an important public health achievement to prevent a disease which can be life-threatening.”

The effort to develop an RSV vaccine started with tragedy in the 1960s, when two toddlers died after receiving an experimental shot. Instead of protecting children in the trial, the vaccine unexpectedly caused them to experience a more dangerous and enhanced version of the illness.

The catastrophe cast a shadow over the field that has lifted only in the last decade following new scientific insights into how a key protein on the surface of the virus changes shape. The detailed knowledge of what that surface protein looks like before it infects cells allowed scientists to design better vaccines and virus-blocking antibodies brewed in a lab.

“This is my life’s work, so it’s kind of amazing to see it come to this point,” said Barney Graham, a vaccine scientist at Morehouse School of Medicine. Graham’s work with Jason McLellan, a structural biologist at the University of Texas at Austin, and Peter Kwong, a vaccine scientist at the National Institutes of Health, helped jump-start the field after decades of failure.

“It’s exciting for me to see this happening because of all the other people who’ve come before me working on RSV, some of whom are no longer with us,” Graham said. “I wish they could see this is happening. It’s been a long struggle.”

GSK’s vaccine, called Arexvy, has been approved in the United States for adults 60 years and older. In a large clinical trial with nearly 25,000 participants, a shot given before RSV season was shown to provide 83% protection against RSV infection deep in the lungs, with even stronger protection against severe illness. The results were published in the New England Journal of Medicine this year.

“Our focus now is to ensure eligible older adults in the U.S. can access the vaccine as quickly as possible and to progress regulatory review in other countries,” the company’s chief scientific officer, Tony Wood, said in a statement on Wednesday.

In March, a committee of external advisers to the FDA voted in favor of GSK’s vaccine, unanimously agreeing that it was effective, and voting 10-2 that it was safe. Safety concerns focused largely on a case of Guillain-Barre syndrome, a rare neurological disorder, in a 78-year-old study participant.

The approval sets the stage for a potential battle between pharmaceutical giants seeking to dominate a multibillion-dollar RSV market. Pharmaceutical company Moderna also has a candidate RSV vaccine but is further behind.

A decision on Pfizer’s RSV vaccine for older adults is expected at the end of May. That vaccine, Abrysvo, got a less favorable endorsement from FDA advisers, with a 7-4 vote that it was safe and effective. Advisers’ safety concerns focused again on the rare risk of Guillain-Barre syndrome. Two 66-year-old participants, one man and one woman, developed symptoms shortly after vaccination.

If Pfizer’s vaccine is approved, the FDA intends to seek a post-marketing safety study.

Experts are also scheduled to meet May 18 to recommend whether a Pfizer maternal vaccination, given during pregnancy, is safe and effective. That vaccine provides protection to newborn babies through an indirect route, as antibodies are passed from parent to child during pregnancy. That gives babies a temporary shield in the vulnerable period after birth. The FDA’s decision is expected in August.

And nirsevimab, a monoclonal antibody for infants that works much like a vaccine, is also under consideration. Vaccines work by showing the body’s immune system a piece of the virus, teaching it to churn out virus-blocking antibodies and other immune defenses.

By contrast, virus-blocking antibodies created in a laboratory can provide an instant dose of protection.

Nirsevimab, developed by Sanofi and AstraZeneca, is already approved in Europe, the United Kingdom and Canada, and the FDA is expected to make its decision in the third quarter.

Graham said the progress expected to unfurl over the next year is gratifying – but that, as is typical in science, more remains to be done. Vaccines for older people, a vaccine during pregnancy and an antibody for infants will help, but the pursuit of an RSV vaccine that can be given directly to young children continues.

“It’s not finished,” Graham said.