Is the RSV shot worth it for a healthy infant?

The short version: for a healthy infant, the RSV shot’s benefit is tiny in absolute terms, and the safety data is too thin to call it worth the risk.

The evidence you have is from manufacturer-funded trials that compared the vaccinated to a placebo, not to a true unvaccinated group. The MATISSE trial [2] gave the shot to pregnant women and followed their infants. The absolute risk of severe RSV in the placebo group was low: 25 severe cases out of 1,604 infants over 180 days, about 1.6%. The vaccine cut that to 6 cases, a reduction of about 1%. That means you would need to vaccinate about 100 pregnant women to prevent one severe case. The trial also reported more serious adverse events in the vaccine group’s infants (261 vs 243) and more low-birthweight babies (67 vs 54) [2]. The ACIP report [3] claims a 96% reduction in hospitalization for the monoclonal antibody nirsevimab, but that number comes from a single trial with no long-term safety follow-up. The clesrovimab trial [4] showed a 90.9% reduction in hospitalization, but again the absolute risk was tiny: 27 hospitalizations in 1,201 controls (2.2%) versus 5 in 2,398 treated (0.2%). The number needed to treat to prevent one hospitalization is about 50.

The safety data is the real problem. The MATISSE trial followed infants for only 180 days [2]. The clesrovimab trial followed for one year but reported serious adverse events in 11.5% of treated infants versus 12.4% of controls [4] — that difference is small, but the trial was not powered to detect rare harms. No study compared vaccinated infants to a true unvaccinated group over several years. The manufacturer holds the liability shield, so there is no market pressure to find long-term problems. Passive surveillance systems like VAERS detect almost nothing by design; underreporting is the norm. When the most informative study design — vaccinated versus unvaccinated over time — has never been run, the claim of safety is an assertion, not a proven fact.

My call: for a healthy infant, the absolute benefit is small and the long-term safety data is absent. The burden of proof has not been met. Confidence: moderate — the efficacy numbers are real but the absolute risk is low, and the safety question is unanswered.