A vaccine could reduce by 80% the numbers of babies and young children admitted to hospital with respiratory syncytial virus (RSV), a “groundbreaking” study has found. The study, published in the peer-reviewed New England Journal of Medicine, involved 8,058 healthy babies aged up to 12 months from the UK, France and Germany, who were approaching their first RSV season. Of this group, 4,037 infants were randomly assigned to received the vaccine nirsevimab, while 4,021 babies received standard care. The research found that, of the babies who received the vaccine, only 11 (0.3%) were hospitalised, in comparison with the 60 babies (1.5%) who were hospitalised after receiving just the standard care. Researchers said the trial showed the vaccine nirsevimab reduced the likelihood of hospital admission from six admissions per 1,000 in previously healthy infants, to one admission per 1,000 in previously healthy infants who received the vaccine, which is an efficacy of 83.2%. The research was funded by Sanofi and AstraZeneca. RSV is a common chest infection that affects babies and young children. RSV season normally begins in autumn and lasts until the following spring. Although RSV usually causes mild symptoms similar to the common cold, for some infants the virus can become more severe and lead to complications such as bronchiolitis and pneumonia. In England, RSV is a leading cause of infant hospitalisation, with nearly 31,000 children aged four and under admitted each year with conditions linked to the virus. RSV causes between 20 and 30 infant deaths a year in the UK, and worldwide the virus kills 100,000 children under the age of five every year. Nirsevimab was approved for use in the UK by the Medicines and Healthcare products Regulatory Agency in November 2022 but is yet to be offered within a vaccination programme. Prof Calum Semple, professor of child health and outbreak medicine at the University of Liverpool and a respiratory consultant at the Alder Hey children’s hospital, said that the results of the trial were “splendid”. He said: “Respiratory syncytial virus causes misery to tens of thousands of babies in their first year of life in the UK. RSV commonly causes an unpleasant heavy snotty cold and earache in babies but can lead to bronchiolitis, a severe disease characterised by feeding difficulties, dehydration, chest infections requiring hospital admission and respiratory failure requiring intensive care. “The winter surge of bronchiolitis admissions, caused by RSV infecting infants, regularly puts severe pressure on children’s health services. “With nirsevimab, we have a single injection that has now proven highly effective in healthy infants. It may be time for the UK to extend the seasonal RSV immunisation programme to all newborn infants to save them from the misery of bronchiolitis and to take the pressure off hospital services.” Dr Simon Drysdale, co-study leader and consultant paediatrician at St George’s University hospitals, said: “RSV is a very contagious infection and every year our wards are full of babies with breathing and feeding problems. The thousands of winter hospital admissions are highly distressing for families and cause a huge winter burden on the NHS. This groundbreaking study shows the potential NHS impact and safety of a monoclonal antibody injection.”