Denmark's rollout of RSV vaccination during pregnancy leads to sharp decline in infant hospitalisations

Denmark’s first winter with maternal RSV immunisation has resulted in a significant reduction in hospital admissions among infants, marking a potential breakthrough in seasonal respiratory illness prevention.

Denmark’s first winter with RSV immunisation in pregnancy has produced two unusually strong early signals. A nationwide evaluation by Statens Serum Institut found that vaccination during pregnancy reduced babies’ risk of RSV-related hospitalisation by 78% in the first six months of life, and by more than 82% among infants younger than three months. Separately, a university-led analysis found that admissions among babies aged up to five months fell to 296 in the 2025-26 season, down from an average of 1,128 across the previous three winters. Denmark introduced the maternal programme on 1 October 2025. (ssi.dk)

The peer-reviewed paper, “Early impact of RSV prevention on infant hospitalisations in Denmark”, was published in The Lancet Regional Health – Europe and is listed under DOI 10.1016/j.lanepe.2026.101750. Written by Caroline Klint Johannesen, Amanda Marie Egeskov-Cavling, Stine Lund, Zitta Barrella Harboe and Thea K. Fischer, it tracked national surveillance data through 29 April 2026. The authors defined an RSV-associated admission as a stay of more than 12 hours with a laboratory-confirmed RSV diagnosis recorded up to four days before or during admission. They estimated an admission rate of 9.9 per 1,000 infants aged 0 to 5 months, with an incidence rate ratio of 0.25 against the previous three-season average. The paper says the 2025-26 season broke clearly from the epidemic curve seen in Denmark’s earlier RSV seasons. (pmc.ncbi.nlm.nih.gov)

The researchers did not claim the vaccine alone caused the collapse in admissions. They described the work as observational and said changes in testing, health-seeking behaviour and wider transmission patterns could also have shaped the figures. Even so, they argued that the timing, size and age pattern of the decline all matched the new prevention strategy, and noted that comparable falls have been reported after RSV immunisation programmes in Belgium, Spain, the Netherlands, France and England. (pmc.ncbi.nlm.nih.gov)

The Danish set-up also went beyond maternal vaccination alone. The published analysis says the national prevention programme combined vaccination in pregnancy with long-acting monoclonal antibody protection for premature infants and other high-risk babies who were not protected through maternal vaccination. Avisen reported that newborns whose mothers were not vaccinated could receive preventive antibodies, underlining that the first season’s drop was recorded in a broader prevention scheme rather than a vaccine-only experiment. (pmc.ncbi.nlm.nih.gov)

That helps explain why Danish officials have stressed both efficacy and uptake. Statens Serum Institut said its first full programme evaluation covered 22,593 children born between November 2025 and March 2026, and that just under 73% were born to mothers vaccinated at least 14 days before birth. Separate uptake figures from the institute show that 16,204 of 22,465 eligible pregnant women accepted the free RSV vaccine in 2025, or about 72%, with coverage highest among babies born in February 2026, when it reached 81%. (ssi.dk)

For hospitals, the effect appears to have been immediate. Fischer said more than 800 infants had avoided a hospital bed over a single winter, calling the result “a remarkable development”, and said paediatric departments around Denmark had escaped the seasonal surge they usually brace for. News24.ro cast the same shift in family terms, describing a winter with far fewer admissions for households with very small babies. Johannesen, the paper’s first author, said it was rewarding to see the research “make a real difference in practice”. (news.ku.dk)

RSV, however, has not disappeared from Danish hospitals. In its summary of the 2025-26 respiratory season, Statens Serum Institut recorded 2,202 RSV-related hospital admissions across all ages and said that, unlike previous seasons, the highest admission incidence was no longer among babies aged 0 to 5 months but among people aged 75 to 84. Fischer has argued that vaccinating older adults matters too. The University of Copenhagen said people over 60 at higher risk, including those with chronic obstructive pulmonary disease, can receive financial support for RSV vaccination, which Fischer believes could bring Denmark “much closer to controlling” the virus’s wider burden. (ssi.dk)

The picture is still evolving. The July national effectiveness assessment was released first as a preprint, while the August university-led paper offers a separate peer-reviewed snapshot of what happened in the first season after rollout. Denmark has already reopened the seasonal offer for pregnant women from 1 May 2026 to 31 January 2027, with vaccination recommended at the routine week-32 pregnancy appointment for women due between July and March. Whether the first winter’s steep fall turns into a durable shift will depend on continued uptake, continued surveillance and what a second season shows. (ssi.dk)