RSV Vaccines That Are FDA-Approved

Fall and winter can be a doozy for respiratory syncytial virus (RSV) infections. For certain demographics — including babies and children with compromised immune systems and adults who are 75 and older or are vulnerable to serious infections — RSV can hit particularly hard. That’s especially true for people who are unvaccinated but eligible.

“RSV season is horrible,” Janet Englund, MD, a pediatrician at Seattle Children’s Hospital and a professor of pediatrics at the University of Washington School of Medicine, said before RSV vaccines received U.S. Food and Drug Administration (FDA) approval for certain individuals. “We are very, very busy, with children lined up in the emergency department waiting for beds in the hospital, which are often already occupied. We also have kids in the emergency department who are too sick to be moved because they need an intensive care unit or acute care, but there’s no place for them to go.”

After decades of research, the FDA approved the first RSV vaccine in 2023. Since then, additional RSV vaccines have become available for older adults, pregnant women, infants, and babies.

RSV Vaccines for Adults

RSV Vaccines for Pregnant Women

In 2023, the FDA approved a Pfizer vaccine under the brand name Abrysvo aimed at protecting infants from RSV via immunizing pregnant women between 32 and 36 weeks of gestation.

“The Pfizer RSV vaccine is a maternal vaccine — the mother is immunized, and the antibodies are passed on via the placenta so that at the time of birth, the baby is protected. This is a type of passive immunity,” says Englund.

“Decreasing the rate of hospitalization in the first 90 days of life is a significant benefit, as the youngest children are at the highest risk for severe RSV,” says Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.

RSV Antibody Treatment for Infants and Babies

These special antibodies are given to the baby as a shot and would last up to five months. In clinical trials, nirsevimab was 79.5 percent effective against RSV-associated lower respiratory tract infections that were serious enough to require medical care, including hospitalization.

Why the RSV Vaccine Took so Long to Develop

After the failed trial, researchers realized there were fundamental scientific problems that needed to be solved to create a successful vaccine, and that's been done only recently, says Dr. Adalja.

In RSV, a molecule called the F protein rearranges its structure when the virus infects and joins with a cell. Researchers determined that the failed RSV vaccines of the past were using F protein in an altered (post-fusion) shape that did not generate beneficial antibodies and actually caused harm, Adalja says.

Using innovative means, researchers were able to “pin” the F protein of RSV in its original correct shape (before it fuses with a cell) to generate the type of immunity that was protective, Adalja explains.

The team that uncovered the solution was led by Barney Graham, MD, a professor at the Morehouse School of Medicine in Atlanta and a former researcher at the National Institute of Allergy and Infectious Diseases (NIAID), who also applied this solution to the SARS-CoV-2 spike protein for the COVID-19 vaccine, says Adalja.

Once a means of accomplishing this was found, vaccine developers were able to move forward, Adalja says. “Multiple companies seized on this opportunity once this basic science problem was solved, due to the enormous burden that RSV exacts, conferring a major market opportunity.”

RSV Vaccines Could Be Game Changers in Public Health

Since the RSV vaccines have been available for only a couple of years, there is still a lack of long-term data to showcase their efficacy in preserving health. However, Adalja is optimistic about the potential. “The approach of RSV vaccines would mark the end of RSV being a major threat to human health,” he says.

Englund adds, “From a public health perspective, I believe these vaccines and treatments mean that we will soon have interventions that can prevent RSV in babies and most vulnerable people.”

In addition to preventing severe illness and death, the vaccines will improve the overall lung health of infants, said Dr. Graham, in an interview in the aforementioned Science article. “If they’re infected with RSV very early in life and develop severe disease, that affects their lung development and overall lung health probably for their lifetime. So the goal here is to really improve overall lung health, and that is something that’s hard to calculate until you’ve seen it evolve over several years,” he said.

Englund hopes the vaccines will be available worldwide and not just in the United States. “In the U.S., we are much better equipped to take care of babies who do get RSV compared to many other countries where babies are much more likely to die of the illness,” she says.