The RSV vaccine is an immunization that protects against respiratory syncytial virus, a common respiratory infection that causes tens of thousands of hospitalizations each year in older adults and infants. Three RSV vaccines are currently licensed in the United States: Arexvy, Abrysvo, and mResvia. They work by training the immune system to recognize and block the virus before it can infect the lungs.
How the Vaccine Works
RSV infects cells by using a protein on its surface called the F protein. Before the virus attaches to a cell, this protein holds a specific shape known as its “prefusion” form. All three licensed RSV vaccines target this prefusion shape, prompting your immune system to produce antibodies that latch onto the virus and prevent it from entering cells.
Two of the vaccines (Arexvy and Abrysvo) deliver a stabilized version of the protein itself. The third, mResvia, uses mRNA technology: instead of injecting the protein directly, it delivers genetic instructions wrapped in tiny fat particles so your cells temporarily produce the protein on their own. Your immune system then recognizes it and builds defenses. The end result is the same across all three: antibodies that neutralize RSV before it can cause serious lung disease.
Who Should Get It
The CDC recommends a single dose of an RSV vaccine for everyone 75 and older. Adults between 50 and 74 are also recommended to get vaccinated if they have conditions that raise their risk of severe RSV illness. Those risk factors include:
- Chronic heart disease such as heart failure or coronary artery disease (high blood pressure alone does not qualify)
- Chronic lung conditions like COPD, emphysema, asthma, or cystic fibrosis
- Weakened immune system from medication or an underlying condition
- Severe obesity with a BMI of 40 or higher
- Diabetes with complications such as kidney disease or nerve damage
- Chronic liver, kidney, or blood disorders like cirrhosis, end-stage kidney disease, or sickle cell disease
- Neurologic conditions that weaken breathing muscles or impair the ability to clear the airway
- Living in a nursing home
The recommendation is for a single dose, not an annual shot. Your provider can also recommend vaccination if other circumstances, such as frailty or living in a remote area far from hospital care, put you at higher risk.
Vaccination During Pregnancy
Newborns are too young to be vaccinated themselves, but pregnant women can pass protective antibodies to their baby before birth. The CDC recommends one dose of Abrysvo (the only RSV vaccine approved for this purpose) between 32 and 36 weeks of pregnancy. Vaccination after 36 weeks and 6 days is not recommended because there isn’t enough time for antibodies to develop and cross the placenta.
In clinical trials, maternal vaccination reduced infant RSV hospitalizations by 68% and RSV-related healthcare visits by 57% within the first three months of life. Protection remained meaningful at six months, with hospitalizations reduced by 57% and healthcare visits by 51%. The vaccine was especially effective against the most dangerous outcomes: the risk of a baby needing intensive care, supplemental oxygen, or mechanical ventilation dropped by 82% in the first three months.
Because this protection gradually fades, vaccination is timed for September through January so the antibodies last through the baby’s first RSV season, which typically peaks in winter.
Monoclonal Antibody Option for Infants
There is a second way to protect newborns. Rather than vaccinating the mother, a preventive antibody called nirsevimab can be given directly to the baby, usually before hospital discharge. This is not a vaccine in the traditional sense. It delivers ready-made antibodies rather than prompting the immune system to build its own.
A large comparative study found that nirsevimab was associated with a 26% lower risk of RSV hospitalization compared to maternal vaccination. The difference was even more pronounced for severe outcomes: babies who received nirsevimab had roughly 42% to 44% lower rates of needing intensive care, ventilator support, or oxygen therapy compared to those protected through maternal vaccination alone. The CDC recommends one strategy or the other for each infant, not both.
How Effective Are the Adult Vaccines
All three vaccines meaningfully reduce RSV-related hospitalizations in older adults, though their efficacy ranges vary. In systematic reviews of clinical trial data, Arexvy reduced RSV-related hospitalizations in older adults by 60 to 65%. Abrysvo showed 58 to 63% efficacy in the same population. mResvia, the mRNA-based option, demonstrated 55 to 58% efficacy against RSV illness.
These numbers are lower than what many people associate with vaccines like measles, but they represent a substantial reduction in a virus that previously had no vaccine at all. The vaccines are most effective at preventing the severe lung infections that lead to hospitalization and complications, which is where the benefit matters most for older adults.
Side Effects and Safety
The most common side effects are typical of any vaccination: soreness at the injection site, fatigue, headache, and muscle pain. These generally resolve within a day or two.
A more serious but rare concern involves Guillain-Barré syndrome (GBS), a condition where the immune system temporarily attacks the nerves, causing weakness and sometimes paralysis. Post-market surveillance data led the FDA to add a GBS warning to both Arexvy and Abrysvo. The estimated risk is about 7 excess cases per million doses for Arexvy and 9 excess cases per million doses for Abrysvo, measured within 42 days of vaccination, in people 65 and older. For context, that means the overwhelming majority of vaccinated individuals will never experience this complication, but it is something to be aware of if you have a history of GBS.
Cost and Insurance Coverage
If you have Medicare Part D, RSV vaccination is fully covered with no copayment or deductible. This applies to all adult vaccines recommended by the CDC’s Advisory Committee on Immunization Practices. Medicare Advantage plans also cover the shot, but only if they include drug coverage. For those with private insurance, coverage varies by plan. Without any coverage, RSV vaccines can cost between $200 and $350 out of pocket, depending on the pharmacy and the specific product.