Maternal RSV Vaccine Cut Infant Hospital Stays 74 Percent in a Pooled Study. Four Studies Back That Number.

What is actually known: RSV vaccination in late pregnancy lowered infant hospitalizations in the phase 3 trials. The CDC recommends either that vaccine or a newborn antibody shot for most babies. A meta-analysis published October 7 in The Lancet Regional Health, Europe now puts real-world protection at 73.6 percent. That figure rests on four studies covering 2,478 infants.

The review, with Evelyn Balsells as first author, screened 5,343 studies and kept 21 that reported real-world data on uptake, effectiveness or safety. Fourteen came from the United States, three each from the United Kingdom and Argentina, and one from France. The authors searched monthly from November 2024 to November 2025 and reported no funding.

Where the 74 percent softens

The confidence interval runs from 66.3 to 81.0 percent, and the heterogeneity statistic across the four studies was 0 percent. But four studies is a small base. The authors say data on narrower age bands, such as under three months versus three to six months, were too sparse to pool. They also found too few reports on effectiveness by week of vaccination to run that comparison. On those questions the evidence is thin.

A French national study published in June in the same journal reached a lower number. Marie-Joelle Jabagi and colleagues used the national health data system. They matched 15,678 infants of vaccinated mothers to 15,678 unimmunised infants born between September 1 and December 31, 2024. They found 50 percent protection against hospitalization for RSV lower respiratory infection (95 percent confidence interval 45 to 55).

The two intervals do not overlap, and the designs differ. The French team followed infants from birth to February 28, 2025, a single RSV season. Cases came from hospital discharge codes, without individual lab results. It also could not rule out bias from health-seeking behavior or vaccine acceptance. Balsells and colleagues list the French figure beside their own. They also list a recent US estimate of 70 percent (95 percent confidence interval 37 to 86).

The 27 percent uptake figure is an average of unlike places

The same review pooled 13 studies covering 1,308,447 US pregnancies. It arrived at 27.1 percent vaccine uptake in the 2023/24 RSV season (95 percent confidence interval 19.1 to 37.0). That was the vaccine's first season in the United States. The heterogeneity statistic was 99.9 percent, meaning nearly all the variation between studies reflects real differences among settings rather than chance. The authors write that the estimate "should be interpreted with caution" because it is "an average across diverse settings in the US."

The CDC's own national estimate from the Vaccine Safety Datalink for that season was 17 percent. The review also cites 38.0 percent for September to December 2024. The authors say these line up with the two ends of their interval. The pooled number describes a first season, not a current national rate.

Abroad, uptake varied with program design. Argentina, which uses the maternal vaccine as its single strategy, reached 62 percent in its first year. In the UK, monthly uptake has stayed under 65 percent. It was 57.8 percent for births in England in August 2025 and 61.5 percent for births in Scotland in October 2025. The lowest figures came from the US and France, where long-acting antibodies for newborns are offered alongside the vaccine. France reported 27 percent in its 2024/25 season, while demand for the antibody reached roughly 80 percent of infants.

The review counts only the maternal vaccine, so a low figure does not say how many babies received protection by either route. The CDC states that most infants will not need both. It recommends one dose of Abrysvo at 32 0/7 through 36 6/7 weeks of pregnancy, given from September to January. For infants outside that window it recommends the antibody nirsevimab.

Who is getting the vaccine

Uptake also tracked access. One UK study in the series found that women in the most deprived areas had 72 percent lower odds of being vaccinated. The comparison group was women in the least deprived areas. The figure comes from a City St George's, University of London release carried by Medical Xpress. The review reports lower uptake among people with limited access to health care and in some ethnic groups, and higher uptake with rising maternal age. It calls the age finding unsettled because the studies were small.

“introducing a vaccine is only the first step”

Khalil chairs the Lancet Regional Health, Europe series that includes the review. The series was presented at the 2026 Global Society for Maternal-Fetal Medicine Congress in Utrecht.

What the safety data cover, and what they leave out

The safety evidence covers less ground than the effectiveness evidence. Three US studies covering 16,394 pregnancies found no significant link between vaccination at 32 to 35 weeks and preterm birth. The odds ratio was 0.99 (95 percent confidence interval 0.87 to 1.10). Preterm birth had been flagged as a signal to monitor after the phase 3 trials, which enrolled people at 24 to 36 weeks. Differences between vaccinated and placebo groups there were not significant.

Every study in the preterm birth analysis came from the US, where vaccination happens after 32 weeks, so it says little about earlier timing. The UK and the WHO advise vaccination as soon as possible after 28 weeks. The review rated ten included studies low risk of bias and five high risk.

Hypertensive disorders of pregnancy are less settled. The studies used different methods and could not be pooled. Logistic regression models found no significant association. A time-to-event analysis found a significantly higher hazard. A US study using Vaccine Safety Datalink data reported an adjusted risk ratio of 1.13 (95 percent confidence interval 1.07 to 1.19). The authors call the findings inconsistent and ask for longer surveillance. They conclude that the risks identified so far do not outweigh the vaccine's favorable safety profile.

Why the first six months

The review cites a 2019 global estimate for children under five. Infants under six months accounted for about 40 percent of RSV-related hospitalizations, roughly 1.4 million, and about half of in-hospital RSV deaths, 13,300. Timing matters because maternal antibodies need days to cross the placenta. The authors report lower effectiveness when the vaccine is received less than 14 days before delivery. The WHO recommends vaccination more than two weeks before birth.

Studies comparing outcomes by week of vaccination and by days before delivery were too sparse to pool, the authors write. Those comparisons would bear on a split among regulators. The US recommends 32 to 36 weeks, while the WHO and the UK advise vaccination soon after 28 weeks.