For most people, this common respiratory virus causes nothing worse than a mild cold. But it’s the No. 1 reason for hospitalization among babies, says Cohen Children’s Medical Center infectious disease specialist Mundeep Kainth, DO, MPH. The pediatric immune system is still underdeveloped and inexperienced at fighting infection. This means trouble in the case of highly contagious viruses like RSV, which can cause inflammation of their tiny airways and leave them struggling to breathe.

Each year, as many as 80,000 children under age 5 are hospitalized because of RSV. Much of that has to do with the way the highly contagious virus spreads: direct contact with the virus, whether through respiratory droplets from an infected individual or by touching something a patient previously touched. This means that younger children, who tend to experience the world through touch and taste, are particularly susceptible to RSV infection.

Because RSV thrives in weaker immune systems, it’s also a problem for older populations; immunity tends to decline as we age. The Centers for Disease Control and Prevention (CDC) estimates that RSV sends between 60,000 and 160,000 older American adults to the hospital each year.

Infection rates typically peak around “RSV season”, or the period of time spanning from the beginning of October to the end of March.

In each case, ACIP reviewed the available body of evidence (such as clinical trial results) and performed a Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) review to determine the benefits and harms of each vaccine. 

Evidence for AREXVY was presented to ACIP June 21, 2023 and included two complete RSV seasons for Northern Hemisphere participants and one complete RSV season for Southern Hemisphere participants. Evidence for ABRYSVO was presented June 21, 2023 and spanned one complete RSV season and part of a second. Lastly, data for mRESVIA was collected from November 2021 to March 2024 and presented to ACIP on June 26, 2024.

Both AREXVY and ABRYSVO belong to a class of vaccines known as recombinant protein vaccines. To make them, genetic material of the virus that codes for certain RSV virus proteins is cloned into a cell. In turn, these cells produce the protein which is then used as the active ingredient in the vaccine. The injected protein triggers an immune response, but because only a part of the virus is present, it can’t replicate inside your body. This makes recombinant protein vaccines both safe and effective.

Other recombinant vaccines include the Hepatitis B and HPV vaccines. 

mRESVIA, by contrast, is a messenger RNA (mRNA) vaccine. This means that it teaches your body how to make a protein that is on the surface of RSV. Your body then produces antibodies for this RSV protein — and remembers how it did it — so it’s prepared to fight a real case of RSV.

Researchers first attempted to develop an RSV vaccine in 1967. In the following decades, virologists began to better understand RSV’s structure and pathology by identifying the types of cells the immune system activates to fight it. By 2015, the World Health Organization predicted — correctly — that an RSV vaccine would be commercially available within 10 years.

The good news is that one vaccine dose will protect you — or, for pregnant women, your child — for one or more RSV seasons, according to the CDC. At present there are no indications for a booster dose of vaccine, Dr. Rubin says. 

Here’s when each group can and should get the RSV vaccine.

RSV vaccine for pregnant women

The RSV vaccine for pregnant women (ABRYSVO) is recommended for use between 32 and 36 weeks of pregnancy from September to January to help protect their newborn infant from serious RSV disease. While vaccines are available year-round, it’s ideal to get vaccinated in late summer and early fall so you’re protected in time for RSV season. This is particularly true, Dr. Kainth explains, for pregnant women. She recommends this group get vaccinated up to a month prior to the start of RSV season in October; this is because their bodies typically need at least two weeks to mount a sufficient antibody response in the event of exposure to RSV.

RSV vaccine for older adults

If you’re 60 or older, you may be eligible for vaccination and can receive any of the RSV vaccines. Experts recommend that you do so ahead of RSV season in late summer or early fall and that you first speak with your doctor.

Current CDC recommendations call for one dose of the vaccine for all adults 75 and older, as well as adults ages 60-74 at an increased risk of severe RSV. For the purposes of these guidelines, the CDC considers the following to be risk factors:

• Heart or lung disease
• Weakened immune system
• Chronic conditions like diabetes and obesity
• Residence in a nursing home

Studies have found that one vaccine dose is enough to protect older adults for up to two years. Ongoing research seeks to determine whether booster shots beyond this period could offer additional protection.

Dr. Rubin added that none of the vaccines are approved for people under 60 except in the case of ABRYSVO for pregnant women. If you’re feeling moderately or severely ill, the CDC recommends waiting until you’ve recovered to receive an RSV vaccine.

Nirsevimab: an antibody shot for infants

• Lung disease
• Cystic fibrosis
• Immune deficiency

Keep in mind that these treatments are a preventive measure; once RSV kicks in, the vaccines and monoclonal antibody won’t be able to help. Instead, infants are managed with supportive care including ensuring adequate fluid intake, or a trip to the emergency room in the event of severe symptoms like blue skin or trouble breathing.

Dr. Kainth says that nirsevimab will likely be given to babies along with their routine vaccinations. “Although there was limited availability of nirsevimab for high-risk children last season, we are currently anticipating that it will be available for everyone in the 2024-25 season,” she noted.

Overall, Dr. Kainth considers the RSV treatments revolutionary and is confident that they will leave hospitals well-equipped to handle the upcoming season: “We think they’ll lead to a massive reduction in the number of cases of RSV. They’re going to change the winter season for babies everywhere.”