A major UK-led clinical trial has found that a treatment commonly used to help premature babies breathe offers no benefit for babies on life support with severe bronchiolitis – a seasonal viral illness that hospitalises thousands of babies each year.
Funded by a partnership between the UK’s UKRI Medical Research Council (MRC) and the National Institute for Health and Care Research (NIHR) and Chiesi Farmaceutici SpA, Italy, the Bronchiolitis Endotracheal Surfactant Study (BESS) trial is the largest randomized study of surfactant for bronchiolitis to date.
The results have been published today (21 March 2026) in The Lancet Respiratory Medicine.
Bronchiolitis occurs when a virus—most commonly respiratory syncytial virus (RSV)—infects a child’s lungs. There is currently no specific treatment for RSV infection, and the disease can be particularly severe in premature and newborn infants. Babies with bronchiolitis have reduced levels of surfactant in the lungs, a condition similar to that seen in premature babies. Because surfactant is routinely used to help premature infants breathe more easily, the study team worked to determine whether this therapy could also benefit hospitalized infants suffering from bronchiolitis.
The study was run in 15 children’s hospitals in England, Scotland and Northern Ireland and involved 232 critically ill babies. However, surfactant did not reduce the time required to stay on a ventilator (life-support breathing machine).
Professor Calum Semple OBE, leader of the study from the University of Liverpool and Alder Hey Children’s NHS Foundation Trust, said: “The treatment was safe, but it didn’t matter how long the children remained on the ventilator. We hoped that surfactant might speed the recovery of these very sick children, but the evidence does not support this.”
Bronchiolitis – often caused by RSV – is the leading cause of hospitalization of babies during winter in the UK. It usually affects babies under one year of age and can be especially severe in babies born prematurely. While most of the twenty-five thousand infants admitted will recover with oxygen and fluids, about a thousand of the most unwell infants require intensive care and a ventilator to assist with breathing. Currently, there is no other treatment for bronchiolitis, but a vaccine is now being offered to mothers-to-be in the last months of pregnancy.
The BESS test was designed to give families and physicians clear answers. It ran over six winter sessions from 2019 to 2024.
While we continue to research better ways to care for these sick babies, I urge expectant mothers to take up the offer of RSV vaccine during pregnancy, which will protect their newborns from severe bronchiolitis.
Calum Semple, University of Liverpool
The researchers emphasize that surfactant therapy is essential for premature newborns and advocate further studies to explore targeted treatments for bronchiolitis.
