Infant RSV admissions fall sharply following vaccine rollout

Denmark’s new respiratory syncytial virus (RSV) vaccination programme for pregnant women may have dramatically reduced the number of infants hospitalised with the virus, according to a new study from the University of Copenhagen and Nordsjællands Hospital suggests that thousands of infants contract 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 autumn 2025, pregnant women in Denmark have been offered an RSV vaccine to help protect their babies during the first months of life.

During the 2025/26 RSV season, the number of hospital admissions among infants aged 0 to 5 months fell by 75 per cent 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 Prof Thea Kølsen Fischer, Clinical Professor at the Department of Public Health and co-author of the study.

The findings are consistent with experiences from countries including Belgium, Spain, the Netherlands, France and England, all of which have introduced RSV vaccination programmes. As well as potential health outcomes, the programme may ease the burden on health services at a crucial time of year.

‘I work in a hospital every day, and colleagues from paediatric departments across the country tell me that the RSV season often places enormous pressure on their services. This year, they have not seen the usual surge in admissions,’ says Prof Kølsen Fischer.

RSV follows a clear seasonal pattern in Denmark, with most hospital admissions occurring between October and March. For that reason, the vaccine is offered to women due to give birth during or shortly before this period. In the first season, 72 per cent of eligible pregnant women accepted the offer of vaccination.

‘It is encouraging that so many women chose to be vaccinated in the first season,’ says Prof Kølsen Fischer.

Despite the sharp decline in admissions, RSV is unlikely ever to disappear completely because it is both widespread and highly infectious. However, researchers believe it may be possible to reduce the burden of severe disease to a much lower level than in previous years.

‘I expect at least as many people to accept the vaccine next season, both because of these early results and because it is a very safe vaccine with very few side effects,’ Prof Kølsen Fischer said.

Older adults at increased risk, including people over 60 with conditions such as chronic obstructive pulmonary disease (COPD), can also receive financial support for vaccination in Denmark which researchers say will have a longer-term impact on the burden of disease.

‘If fewer older people become seriously ill, I believe we will move much closer to controlling a virus that has traditionally caused a large number of sick days and hospital admissions,’ she says.