Important: VAERS reports alone cannot determine if a vaccine caused an adverse event. Reports may contain incomplete, inaccurate, or unverified information. Correlation does not equal causation.
Respiratory syncytial virus (RSV) protection has expanded rapidly. Heading into the 2025–2026 season there are now vaccines for older adults and pregnant women, plus a long-acting antibody for infants. Here is who qualifies, how well they work, and what the reported side effects look like.
The approval of RSV vaccines in 2023–2024 represented a decades-long effort to develop protection against a virus that has eluded vaccine developers since the 1960s. An early attempt at an RSV vaccine in the 1960s actually made disease worse in vaccinated children (a phenomenon called vaccine-enhanced disease), setting back RSV vaccine research by decades. Modern RSV vaccines use fundamentally different approaches that avoid this risk.
RSV is a common respiratory virus that causes cold-like symptoms in most people but can be serious for infants and older adults. It is a leading cause of hospitalization in babies and is responsible for tens of thousands of hospitalizations and thousands of deaths among older adults in the United States each year. For decades there was no approved RSV vaccine; the arrival of multiple products has made the 2025–2026 season a turning point in prevention.
Arexvy, manufactured by GSK, is a protein subunit vaccine with an adjuvant that boosts the immune response. It is approved for adults 60 and older and given as a single dose. In its pivotal trial, Arexvy substantially reduced RSV-associated lower respiratory tract disease in older adults, with protection observed across the first two seasons. It is not an mRNA vaccine.
Abrysvo, made by Pfizer, is a bivalent protein-based vaccine with two important uses. First, like Arexvy, it protects adults 60 and older. Second — and uniquely — it is approved for pregnant women at 32–36 weeks of gestation. When given during this window, the mother produces antibodies that cross the placenta and protect the newborn during the first vulnerable months of life. Maternal vaccination is administered seasonally (typically September through January in most of the country) to align protection with peak RSV circulation.
Nirsevimab, sold as Beyfortus, is not a vaccine but a long-acting monoclonal antibody. Rather than training the immune system, it delivers ready-made antibodies that provide passive protection lasting through an RSV season. CDC recommends it for infants under 8 months entering their first RSV season who are not already protected by maternal Abrysvo vaccination, and for some high-risk children 8–19 months entering their second season. In real-world use it has markedly reduced medically attended RSV illness and hospitalization in infants.
Families generally choose one approach to protect a newborn: either maternal vaccination during pregnancy or nirsevimab for the infant after birth. Both are effective; the choice depends on timing, availability, and a discussion with the healthcare provider.
The adult RSV vaccine is currently a single dose — it is not yet an annual vaccine like flu or COVID-19. Whether and when a booster will be recommended is an area ACIP continues to study.
Across clinical trials, the adult RSV vaccines reduced RSV-associated lower respiratory tract disease by roughly 70–83% in the first season, with meaningful protection continuing into a second season. Maternal vaccination with Abrysvo cut severe RSV disease in infants during the first months of life, and nirsevimab reduced medically attended infant RSV illness by approximately 75–80% in trials and real-world studies. Efficacy naturally wanes over time, which is why timing relative to the season matters.
The most frequently reported reactions to RSV vaccines are local and short-lived: injection-site pain, fatigue, muscle aches, headache, and low-grade fever, usually resolving within a few days. A small number of Guillain-Barré syndrome cases were observed in older-adult trials, prompting continued safety monitoring; the absolute risk appears very low and is weighed against the substantial burden of RSV disease in this age group. You can read more about that condition in our Guillain-Barré overview.
VaccineWatch tracks 9,330 VAERS reports mentioning RSV vaccination. As with all passive surveillance, these reports describe events that occurred after vaccination and do not on their own establish causation. For a deeper explanation, see the denominator problem and is VAERS reliable?
Since RSV vaccines became widely available in the 2023–2024 season, real-world data has begun to confirm the clinical trial findings. Key observations from the first two seasons of use include:
RSV season in most of the continental United States typically runs from October through March, with peak activity in December and January. This seasonality matters because:
Some southern states and tropical regions experience earlier or longer RSV seasons, and healthcare providers in those areas may adjust timing accordingly.
For the first time, effective RSV prevention is available across the age spectrum — from newborns to seniors. If you are 75 or older, 60–74 with risk factors, or pregnant in the fall, talk with your provider about which option fits you. RSV vaccination is now part of the broader CDC vaccine schedule, and it features prominently in this year's updates covered in our 2026 vaccine schedule guide.