Thousands of infants contract respiratory syncytial virus (RSV) every year. While most experience mild symptoms, the virus can cause severe breathing difficulties in newborns and young infants and may require hospital treatment. Since fall 2025, pregnant women in Denmark have been offered an RSV vaccine to help protect their babies during the first months of life.
New findings from the University of Copenhagen and Nordsjællands Hospital now point to a substantial reduction in hospital admissions among the youngest children. The paper is published in The Lancet Regional Health—Europe.
During the 2025–26 RSV season, the number of hospital admissions among infants ages 0–5 months fell by 75% compared with the average of the previous three seasons. While admissions averaged 1,128 in those years, only 296 infants were admitted between October and April in the most recent season.
"That's more than 800 infants who avoided hospital admission over the winter. For these very young children, RSV can be particularly serious and may cause severe breathing difficulties. It is a major strain on both children and their families, so this is a remarkable development," says Thea Kølsen Fischer, clinical professor at the Department of Public Health and co-author of the study.
