Abrysvo is a vaccine that protects against respiratory syncytial virus (RSV), a common respiratory infection that can be dangerous for newborns and older adults. It is the only RSV vaccine approved for use during pregnancy, where a single shot given to the mother shields her baby for months after birth. It is also approved for older adults at risk of severe RSV illness.
Who Abrysvo Is Approved For
The FDA has approved Abrysvo for three groups:
- Pregnant individuals at 32 through 36 weeks of pregnancy, to protect their infants from RSV lung infections from birth through 6 months of age.
- Adults 60 and older for prevention of RSV-related lower respiratory tract disease.
- Adults 18 through 59 who have health conditions that put them at higher risk for severe RSV illness.
Current CDC recommendations narrow the focus a bit further for older adults. The agency recommends a single dose for all adults 75 and older and for adults 50 to 74 who have conditions that raise their risk of severe RSV. Those conditions include chronic lung disease, heart failure, severe obesity (BMI of 40 or higher), moderate or severe immune compromise, diabetes with organ damage, chronic liver or kidney disease, neuromuscular conditions that weaken breathing, and residence in a nursing home.
How It Protects Newborns
RSV is one of the leading causes of hospitalization in infants. Babies are too young to be vaccinated themselves in the first months of life, so Abrysvo works around that problem. When given to a pregnant person during the third trimester, the vaccine prompts the mother’s immune system to produce protective antibodies that cross the placenta and reach the baby before birth.
The timing window matters. The vaccine should be given between 32 weeks and 36 weeks, 6 days of pregnancy. Getting it earlier than 32 weeks is not recommended because of a potential risk of preterm birth observed in clinical data. Getting it after 36 weeks and 6 days leaves too little time for antibodies to build up, cross the placenta, and reach protective levels in the baby.
In the large phase 3 MATISSE trial, maternal vaccination showed strong results. The vaccine was 81.8% effective at preventing severe RSV lung infections in infants during the first 90 days of life. At 180 days (six months), efficacy against severe infections was 69.4%, and efficacy against medically attended RSV lung infections was 57.1%. That means the protection is strongest in the first three months, when babies are most vulnerable, and gradually decreases over the following months.
How It Works in Older Adults
RSV causes tens of thousands of hospitalizations and several thousand deaths among older adults in the United States each year. The virus is especially dangerous for people with weakened lungs, compromised immune systems, or other chronic health problems. Abrysvo targets the protein RSV uses to enter cells, training the immune system to block the virus before it can cause a serious lung infection.
Clinical trial data pooled from large phase 3 studies showed a vaccine efficacy of about 73% in adults aged 60 to 74 who had underlying health conditions that raised their risk. In adults 75 and older, efficacy was roughly 69%. Both figures reflect meaningful reductions in RSV-related lower respiratory tract disease compared to placebo.
Dosing and Timing
Abrysvo is a single shot, given as a 0.5 mL injection. For both older adults and pregnant individuals, only one dose is needed. It is not an annual vaccine like the flu shot, so you do not need to repeat it every season.
For older adults, the vaccine can be given at any time of year, but it offers the most benefit when administered in late summer or early fall, just before RSV season picks up. In most of the continental United States, that means getting vaccinated during August through October. For pregnant individuals, the timing is determined by gestational age rather than the calendar, though providers may factor in seasonal RSV activity when counseling patients.
Common Side Effects
Side effects of Abrysvo are generally mild and short-lived, consistent with what you would expect from most vaccines. The most frequently reported reactions include pain, redness, or swelling at the injection site, along with fatigue, headache, and muscle pain. These typically resolve within a day or two.
For pregnant individuals, the key safety consideration is the timing restriction. Administration before 32 weeks of pregnancy is specifically avoided because of a signal for preterm birth seen in clinical trial data. Within the approved 32 to 36 week window, the safety profile has been reassuring enough for both the FDA and CDC to recommend the vaccine.
Abrysvo vs. Other RSV Prevention
For infants, Abrysvo is an alternative to nirsevimab, a monoclonal antibody given directly to the baby after birth. The two options are not typically given together. If the mother received Abrysvo during pregnancy and the baby is born before RSV season, the infant generally does not also need the antibody injection, though specific situations may vary.
For older adults, the other available RSV vaccine is Arexvy, made by GSK. Both target the same RSV surface protein and have similar efficacy profiles. The CDC does not express a preference between the two for older adults. Your provider may stock one or the other, and either option fulfills the recommendation for a single RSV vaccination.