The first RSV vaccine was approved in the United States on May 3, 2023, making it roughly two years old as of mid-2025. For a virus discovered in 1956, that’s a remarkably recent breakthrough. Scientists spent decades trying and failing to develop a safe RSV vaccine before three products reached the market in quick succession.
The Approval Timeline
GSK’s Arexvy was the first across the finish line, receiving FDA approval on May 3, 2023, for adults 60 and older. Pfizer’s Abrysvo followed months later, approved for both older adults and as a maternal vaccine given during pregnancy to protect newborns. Moderna’s mRESVIA came next in 2024, becoming the first mRNA-based RSV vaccine to reach the market. All three arrived within about a year of each other, ending a long period in which RSV was one of the last major respiratory viruses without an available vaccine.
Why It Took So Long
RSV has been a known threat since the 1950s, but early vaccine attempts backfired badly. A trial in the 1960s using an inactivated version of the virus actually made disease worse in children who later caught RSV, hospitalizing many and killing two. That disaster halted RSV vaccine research for years and made regulators and scientists extremely cautious. The breakthrough that eventually unlocked these vaccines was figuring out how to stabilize a key protein on the virus’s surface (the prefusion F protein) in the right shape to train the immune system effectively. That structural biology work, done in the 2010s, is what made all three current vaccines possible.
How the Three Vaccines Differ
Arexvy and Abrysvo both use a protein-based approach: they deliver a lab-made version of the RSV surface protein directly into your body to trigger an immune response. Moderna’s mRESVIA uses mRNA technology similar to the COVID-19 vaccines, delivering genetic instructions that tell your cells to build that same protein temporarily. All three target the same viral protein, just through different delivery methods.
Who Should Get It
Current CDC guidelines recommend the RSV vaccine as a single dose for all adults 75 and older. Adults between 50 and 74 are also recommended to get it if they have conditions that raise their risk of severe RSV illness. Those conditions include chronic heart or lung disease, a weakened immune system, diabetes with organ damage, severe obesity (BMI of 40 or higher), chronic liver or kidney disease, neurological conditions that affect breathing or swallowing, and living in a nursing home.
For infant protection, pregnant women can receive Abrysvo between 32 and 36 weeks of pregnancy. The vaccine prompts the mother’s immune system to produce antibodies that cross the placenta and shield the baby during their first RSV season. In the phase 3 clinical trial, maternal vaccination reduced the risk of an infant being hospitalized for RSV by 68% within the first three months of life, and by 57% within six months. Protection against the most severe outcomes, like needing intensive care or mechanical ventilation, was even stronger: 82% in the first three months and 69% within six months.
How Well It Works
Because these vaccines are so new, researchers are still tracking how protection holds up over time. The clearest long-term data comes from GSK’s Arexvy. In the first RSV season after vaccination, a single dose prevented 82.6% of lower respiratory tract disease in older adults. That protection dropped to 56.1% in the second season and 48.0% in the third, for a cumulative efficacy of about 63% across all three seasons. That waning pattern is one reason the current recommendation is framed as a single dose rather than an annual shot, though guidelines could evolve as more data comes in.
Side Effects and Safety Signals
The most common side effects are what you’d expect from any vaccine: injection site pain (reported by about 31% of recipients), fatigue (around 21%), and muscle aches (about 18%). These typically resolve within a day or two.
One safety signal that drew early attention is Guillain-Barré syndrome (GBS), a rare neurological condition where the immune system attacks nerve cells. Reports of GBS after RSV vaccination have been higher than the expected background rate in the general population. The reporting rates were approximately 4.4 cases per million doses of the Pfizer vaccine and 1.8 per million doses of the GSK vaccine. Those numbers are small in absolute terms, but they prompted the CDC and FDA to launch ongoing population-based surveillance to better understand the risk. This monitoring effort is part of why the recommended age was narrowed from 60 and older to focus on those 75 and older or 50 and older with specific risk factors, concentrating the vaccine’s use where the benefit most clearly outweighs potential risks.