Vaccines to prevent RSV in adults may be available in the United States by spring 2023. They would help address the burden of RSV in older adults and could help prevent infection in infants through vaccination of pregnant individuals.

Respiratory syncytial virus (RSV) can infect the lower respiratory tract. While RSV usually causes mild, cold-like symptoms, it can be serious or even fatal in infants, older adults, and people with compromised immune systems.

In the U.S., RSV infections cause more than 60,000 hospitalizations and 6,000 deaths in older adults each year. In addition, the Centers for Disease Control and Prevention (CDC) reported an increase in both infections and hospitalizations from the virus during the 2022–2023 flu season.

The virus is highly contagious and can spread through droplets that release into the air when a person who has the virus coughs or sneezes. A person can also contract the virus by touching a contaminated surface or through direct contact with a person who has the virus, such as kissing.

At the time of writing, no approved vaccines against RSV are available for adults in the U.S. However, a few vaccines may gain approval as soon as this year.

Researchers are developing several vaccines to prevent RSV infections in adults, but the Food and Drug Administration (FDA) has not yet approved any. The FDA’s advisory panel recently voted to recommend approval of two vaccines, both of which could be available by this summer.

RSV vaccine history

Scientists developed an RSV vaccine for infants in the 1960s. However, they stopped its development because of concerns about a severe lung inflammatory response that occurred in some vaccinated infants and resulted in two deaths.

Though it has taken time, new technological advances and a better understanding of RSV have resulted in several promising vaccine candidates in recent years.

Vaccine candidates

Researchers are studying at least five adult RSV vaccines in late stage clinical trials:

The Pfizer and GlaxoSmithKline vaccines are the two that the FDA advisory panel already voted to approve.

Ongoing clinical trials are studying how different populations, such as older adults, respond to RSV vaccines. These trials will help shape the public guidance on who would benefit most from and should get the vaccines.

RSV vaccines work by teaching the body to recognize key proteins that RSV uses to attack human cells.

Once a person receives an injection of a vaccine containing these proteins or instructions to make them, the body’s immune system produces antibodies to fight them.

The immune system remembers how to protect the body against this antigen in the future. If the body encounters RSV later, the immune system will be able to quickly recognize the virus and disable it to prevent infection.

Most vaccine candidates in development are based on a stabilized version of RSV’s prefusion F protein.

Moderna is using the same mRNA technology in its RSV vaccine that it used to develop its SARS-CoV-2 vaccine. Moderna’s RSV vaccine contains mRNA coding for the prefusion F protein. A person’s body produces this protein after they receive the vaccine injection.

Janssen’s vaccine candidate contains a combination of the RSV prefusion F protein and a modified adenovirus that produces prefusion F after a person receives the vaccine injection.

Another viral vector vaccine, sponsored by Bavarian Nordic, contains genes for five RSV antigens, including the F protein. The company hopes this approach will be more advantageous than focusing on only one protein.

The FDA may approve the first RSV vaccines for adults in May 2023. The FDA will make a decision after reviewing effectiveness and safety data from the vaccines’ clinical trials.

In clinical trials, Pfizer’s vaccine was more than 85% effective in preventing laboratory-confirmed lower respiratory tract disease (LRTD) from RSV infection with 3 or more symptoms. The most common side effects among people receiving the vaccine were fatigue, headache, and pain or muscle soreness at the injection site.

GlaxoSmithKline’s vaccine also met its primary endpoint in clinical trials, with more than 82% effectiveness against RSV LRTD and 94% reduction in severe RSV disease. The most common side effects were fatigue, muscle soreness, and headache.

The Prescription Drug User Fee Act (PDUFA) goal dates for FDA decisions on both vaccines in adults aged 60 years and older are in May 2023. The FDA must complete its review by this time.

Pfizer is also seeking approval of the vaccine for use in pregnant individuals to help protect infants from RSV infection. For this population, the FDA has set a PDUFA action date in August 2023.

Several other vaccines may follow in the coming years.

RSV causes mild, cold-like symptoms in most adults, so vaccines would not be necessary for everyone.

Once regulatory agencies approve an adult RSV vaccine, health experts may recommend it for:

  • People aged 60 or 65 years and older: It is unclear whether the FDA will approve use of the vaccine in people aged 60 years and older or restrict its use to people aged 65 years and older.
  • Pregnant individuals: The vaccine could help protect against the complications of RSV disease in infants.

Official recommendations will come from the FDA and organizations such as the CDC’s Advisory Committee on Immunization Practices.

People aged 60 years or older and pregnant individuals can ask a doctor about getting an RSV vaccine once it becomes available.

The vaccine will not be available until the FDA approves it.

Several promising vaccine candidates are in late stages of development or under formal FDA review to prevent RSV in older adults and pregnant individuals. The first vaccine candidates could be available as soon as this year if the FDA approves them.

Until then, it is important to take extra care to prevent the spread of this contagious virus by:

  • washing hands often
  • avoiding close contact with people who are sick
  • disinfecting frequently touched surfaces
  • staying home while sick