A major UK-led clinical trial has found that a treatment commonly used to help premature babies breathe offers no life-supporting benefit for infants with severe bronchiolitis – a seasonal viral illness that hospitalises thousands of babies each year.
Funded by a collaboration between the 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) is the largest ever randomized study of surfactant for bronchiolitis.
The results are published today (March 21, 2026) in The Lancet Respiratory Medicine.
Bronchiolitis occurs when a virus—most commonly respiratory syncytial virus (RSV)—infects a baby’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 their lungs, a condition similar to that seen in babies born prematurely. Because surfactant is routinely used to help premature infants breathe easier, the study team decided to determine whether this treatment could also benefit babies hospitalized with bronchiolitis.
The study was carried out in 15 children’s hospitals in England, Scotland and Northern Ireland and involved 232 critically ill babies. However, the surfactant did not reduce the time they needed to be on a ventilator (life support breathing machine).
Professor Calum Semple OBE, who led the study from the University of Liverpool and Alder Hey Children’s NHS Foundation, said: “The treatment was safe, but it made no difference to how long the babies stayed on ventilators. We had hoped that the surfactant might speed up recovery for these very sick babies, but the evidence doesn’t support that.”
Bronchiolitis – most commonly caused by RSV – is the main reason babies are admitted to hospital in the UK during the winter. It usually affects babies under one year of age and can be particularly severe in those born prematurely. While most of the twenty-five thousand babies admitted will recover on oxygen and fluids, about a thousand of the sickest need intensive care and a ventilator to support their breathing. Currently, there is no other treatment for bronchiolitis, but a vaccine is now offered to expectant mothers in the last few months of pregnancy.
The BESS trial was designed to give families and clinicians clear answers. It ran for six winter seasons from 2019 to 2024.
While we continue to research better ways to care for these sick babies, I urge moms-to-be to take up the offer of the RSV vaccine during pregnancy, which will protect their newborn babies from severe bronchiolitis.”
Calum Semple, University of Liverpool
The researchers stress that surfactant therapy remains essential for premature newborn babies and support further studies investigating targeted therapies for bronchiolitis.
