How Often Do You Have to Get the RSV Vaccine?

Right now, the RSV vaccine for older adults is recommended as a single dose with no scheduled booster. When the Advisory Committee on Immunization Practices (ACIP) first recommended RSV vaccines for adults aged 60 and older in June 2023, the guidance was one shot, period, because there wasn’t enough evidence to say whether or when a second dose would be needed. That question remains officially unanswered, but clinical trial data tracking protection over two or more seasons is starting to fill in the picture, and cost-effectiveness studies are already modeling what a repeat-vaccination schedule might look like.

What the Current Recommendation Actually Says

ACIP recommended that adults aged 60 and older may receive a single dose of an RSV vaccine through shared clinical decision-making with their healthcare provider. The key word is “may” rather than “should,” meaning the decision depends on individual risk factors like chronic lung or heart disease, living in a nursing home, or general frailty. The recommendation explicitly noted that there was not yet enough evidence to determine the need for revaccination.¹

This is a different setup from, say, your annual flu shot. Nobody is telling you to come back next fall for another RSV vaccine. At the same time, nobody is telling you one dose will last forever. The guidance essentially says: get your single dose, and stay tuned. As more data arrives from ongoing clinical trials, the recommendation will be updated.

How Long Does a Single Dose Protect You?

The most detailed look at how protection fades over time comes from the trial behind the GSK vaccine (Arexvy). A single dose prevented about 83% of RSV-related lower respiratory tract disease through the first season, but that number dropped to about 67% when tracked across two full seasons, with a median follow-up of roughly 18 months. Against severe disease, efficacy held up better, staying near 79% over two seasons. Against any RSV-related acute respiratory illness, protection was lower at about 53% over the same period.²

The pattern is what you’d expect: protection starts strong and gradually declines. Measured at different time points, efficacy against lower respiratory tract disease went from about 83% at roughly seven months, to 79% at one year, to 77% at about 14 months, down to 67% across the full two-season span. The decline is real, but even at two seasons, you’re still getting meaningful protection against the most dangerous outcomes.

Moderna’s mRNA-based vaccine (mRNA-1345) showed roughly 84% efficacy against RSV-associated lower respiratory tract disease with at least two symptoms in its pivotal first-season trial, along with about 68% efficacy against acute respiratory disease more broadly.³ In a separate phase 1 study, antibody levels remained above their pre-vaccination baseline through 12 months, though they were clearly trending downward by that point.⁴

So the honest answer is that a single dose looks solid through one RSV season, still useful but fading through a second, and beyond that we’re mostly guessing. That fading is the engine behind the entire booster conversation.

Does a Booster Shot Help?

This is where the evidence gets surprisingly complicated. In the GSK trial, a subset of participants received a second dose before their second RSV season, about a year after the first. The two-season efficacy for people who got that booster was essentially identical to the efficacy for those who received only one dose: about 67% against lower respiratory tract disease and 79% against severe disease. In other words, revaccination at the one-year mark did not seem to add meaningful clinical benefit over a single dose.²

That finding may sound discouraging if you were hoping for a clear booster path, but it makes some immunological sense. If your antibody levels are still reasonably high from the first dose, a second dose a year later may not push them meaningfully higher. The immune system’s response to repeated stimulation isn’t always additive, especially with protein-based vaccines targeting the same antigen.

Longer gaps between doses tell a different story. A phase 2b study of the Pfizer vaccine (Abrysvo) found that a third dose given about 18 months after a two-dose primary series boosted neutralizing antibody levels against both RSV-A and RSV-B subtypes, though peak titers after the third dose didn’t quite reach the heights seen after the very first dose. Side effects remained mostly mild to moderate, and no serious vaccine-related adverse events were reported.⁵

For the Moderna mRNA vaccine, a booster given 12 months after the initial dose was well tolerated and bumped antibody levels back up, though again not quite to the peak reached after the first injection. Reactogenicity was somewhat higher after the booster than after the first shot, but the reactions had a similar profile: injection-site pain, fatigue, headache, and muscle aches.⁴ A separate study looking at revaccination 24 months after the first dose found that antibody responses met the pre-specified bar for being non-inferior to the response seen after the original shot.⁶

The emerging picture suggests that revaccination too early (around one year) might not add much, while waiting two years or more could better align with the natural waning of first-dose protection. But translating antibody measurements into real-world disease prevention takes larger and longer trials, and those are still underway.

What Timing Might Make Sense for Repeat Doses?

Nobody has issued an official booster recommendation yet, but cost-effectiveness modeling is helping frame the question. A Dutch study evaluated various repeat-vaccination strategies over six RSV seasons and found that vaccinating every three years was the most cost-effective approach. Strategies that revaccinated every two years had higher costs relative to their health gains and were dominated in the incremental comparisons.⁷ A Canadian multi-model comparison also evaluated scenarios assuming either two or three years of vaccine protection, considering different combinations of age and underlying medical conditions.⁸

These models don’t set policy, but they hint at where the field is heading: the most likely future schedule probably looks like a dose every two to three years rather than an annual shot. That said, the final answer will depend on longer-term efficacy data that doesn’t exist yet, the price of vaccines, and how individual risk factors (age, chronic illness, immune status) shift the calculation for different groups.

People With Weakened Immune Systems

If you’re immunocompromised, the waning of vaccine protection after a single dose may be steeper than it is for the general older adult population. Two-season analyses suggest that the decline in protection is more pronounced in people with compromised immune function.⁹ This isn’t unique to RSV; it’s a well-known pattern across vaccines for conditions like organ transplant recipients, people on certain cancer therapies, and those with HIV.

The practical implication is that immunocompromised individuals may eventually be recommended for earlier or more frequent revaccination than the general population. For now, though, the same single-dose recommendation applies, and the shared clinical decision-making framework lets your provider weigh your specific situation.

Can You Get the RSV Vaccine Alongside Your Flu Shot?

Yes. A phase 3 trial found that giving the GSK RSV vaccine at the same time as an adjuvanted seasonal influenza vaccine in adults 65 and older produced acceptable reactogenicity and safety profiles, without clinically meaningful interference with the immune response to either vaccine.¹⁰ This matters practically because most older adults are already making a trip for their annual flu vaccine in the fall, and being able to get both at once removes a scheduling barrier. If you’re wondering whether eventual RSV boosters could be timed alongside flu shots in future years, the early data suggests that pairing makes logistical and immunological sense.

RSV Prevention for Babies Is a Different Story

The schedule for protecting infants from RSV looks nothing like the adult vaccine picture, because infants aren’t getting vaccinated themselves. Instead, there are two strategies: vaccinating the mother during pregnancy so that antibodies cross the placenta, or giving the newborn a monoclonal antibody injection. Neither involves the baby’s own immune system generating a lasting response, so the protection is temporary by design.

Maternal RSV vaccination works by boosting the mother’s existing memory B cells, which ramps up antibody production. Those antibodies cross the placenta and protect the baby during the first five to six months of life.¹¹ A modeling study estimated that a baby born at full term would be protected from RSV-A-related mortality for roughly six to seven months and from RSV-B-related mortality for about five months.¹² This is a one-pregnancy, one-dose approach. It doesn’t require boosters because the goal is protecting one specific baby through their most vulnerable months, not building the mother’s long-term immunity against RSV.

The alternative for newborns is nirsevimab, a monoclonal antibody given as a single intramuscular injection. It isn’t a vaccine at all; it’s a lab-made antibody that provides passive protection for at least five months.¹³ Because it was engineered with an extended half-life of roughly 69 days, a single dose pushes neutralizing antibody levels to more than 140-fold above baseline by one month, and those levels remain more than 50-fold above baseline at five months. Even at one year, levels were still on average more than seven times higher than pre-injection baseline, suggesting some residual protection beyond a single RSV season.¹⁴ The current guidance is one dose ahead of the baby’s first RSV season, with no routine second dose required for most infants.

Why RSV Doesn’t Work Like Measles for Immunity

If you’ve ever wondered why you can catch RSV over and over while a measles vaccine lasts decades, the difference comes down to how the immune system handles these two viruses. RSV does not generate the kind of durable, sterilizing immunity that measles does. Adults get reinfected with RSV repeatedly throughout life, and each natural infection boosts antibodies temporarily before they wane again. The vaccine, in a sense, mimics this pattern: it gives a strong initial push that erodes over one to two years.

Research into immune correlates of protection has identified minimum thresholds of neutralizing antibody levels that reduce the risk of RSV-associated hospitalization, but these thresholds represent a floor rather than a permanent shield.¹⁵ Once antibody levels drift below that floor, you become susceptible again. And because RSV doesn’t mutate as dramatically as influenza, the issue isn’t a new strain evading your immunity each year; it’s that the antibody levels simply don’t persist the way they do for some other infections.

A study comparing antibody durability in vaccinated pregnant women and vaccinated older adults found that by 12 to 15 months after vaccination, antibody levels were similar between the two groups, suggesting that the rate of waning is fairly consistent across these populations.¹⁶ Understanding this pattern matters for predicting when boosters might become necessary: if antibodies fall below protective thresholds somewhere around the two-year mark for most people, that sets a rough biological clock for repeat dosing.

What to Do Right Now If You Haven’t Been Vaccinated

If you’re 60 or older and haven’t received an RSV vaccine, the current guidance says you can get a single dose after discussing your risk profile with your provider. The conversation typically weighs factors like chronic lung disease (COPD or asthma), heart disease, diabetes, living in a long-term care facility, or being 75 or older regardless of other conditions. If any of those apply, the benefit of vaccination is clearer. If you’re a healthy 60-year-old with no major risk factors, the case is weaker, and shared decision-making is meant to let you and your provider sort that out together.

If you’ve already been vaccinated, there is currently no recommendation for a second dose. At present, people who have already received an RSV vaccination are not advised to get another one, and the ideal timing for revaccination remains unknown.¹ That will almost certainly change as trial data matures, and the likeliest eventual schedule looks to be somewhere in the range of every two to three years rather than annually. But until ACIP updates its guidance, asking for a booster will likely result in your provider telling you to wait.

How the RSV Vaccine Schedule Compares to Other Adult Vaccines

The one-dose-and-wait approach feels unfamiliar if you’re used to the annual flu shot cadence, but it actually has more in common with the shingles vaccine (Shingrix) or the pneumococcal vaccines, which are given as a short series and then not repeated. RSV occupies an in-between zone: the protection doesn’t seem permanent like measles but doesn’t vanish as quickly as flu immunity tends to, partly because influenza’s rapid mutation is the main driver behind annual reformulation of that vaccine. RSV changes more slowly, so the same vaccine formulation stays relevant longer.

If a booster schedule does get established in the coming years, it could end up being the first non-annual repeat vaccine that many older adults encounter. That will require some public health messaging to navigate, since “get vaccinated every two to three years” is a harder habit to maintain than either “once and done” or “every fall.” Health systems will need reminders built into their outreach, and individuals will need to track their vaccination dates in a way that doesn’t fit neatly into an annual calendar.