RSV Hospitalizations Plummet Among Danish Infants After Vaccine Rollout

Denmark's national vaccination program for pregnant women has demonstrably reduced hospitalizations for respiratory syncytial virus (RSV) among infants, according to the first evaluation of its effectiveness.

The program, which began offering the RSV vaccine to pregnant individuals in the fall, has led to a significant drop in severe cases. Data from 22,593 infants born between November 2025 and March of this year shows that only 66 infants born to vaccinated mothers were hospitalized with RSV, representing about 0.4% of that group. In contrast, 104 infants born to unvaccinated mothers were hospitalized, a rate of 1.7%.

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The marked reduction in the number of RSV-related hospitalizations among the youngest infants reflects both a high vaccine effectiveness and the excellent uptake of the vaccination program among pregnant women.

RSV is a contagious respiratory infection that can cause severe illness in infants due to their underdeveloped immune systems and narrow airways, which can become blocked by inflammation and mucus, making breathing difficult. Danish health authorities emphasize the critical importance of vaccinating pregnant women to protect their newborns.

Bolette Søborg, a section head and senior physician at the Statens Serum Institut (SSI), stated that the "marked reduction" in RSV-related hospitalizations among the youngest infants reflects both high vaccine effectiveness and strong uptake among pregnant women. The Danish Health Authority announced in May that the vaccine would again be offered to pregnant individuals, following its proven success in preventing hospitalizations.

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It shows that the program has already had a clear effect after the first season.