UK study finds no added benefit of surfactant treatment for babies with severe bronchiolitis
A major UK-led clinical trial has found that a treatment commonly used to help premature babies breathe offers no benefit for infants 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 National Institute for Health and Care Research (NIHR), and by Chiesi Farmaceutici SpA, Italy, the Bronchiolitis Endotracheal Surfactant Study (BESS) trial is the largest-ever randomised study of surfactant for bronchiolitis.
The results are published today (21 March 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 illness can be especially 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 more easily, the study team set out to determine whether this therapy could also benefit babies hospitalised with bronchiolitis.
The study ran across 15 children’s hospitals in England, Scotland, and Northern Ireland and involved 232 critically ill babies. However, surfactant did not reduce the time they needed to be on a ventilator (life-support breathing machine).
Professor Calum Semple OBE, the study’s lead from the University of Liverpool and Alder Hey Children’s NHS Foundation Trust, said: “The treatment was safe, but it didn’t make any difference to how long babies stayed on ventilators. We had hoped that surfactant might speed up recovery for these very sick babies, but the evidence doesn’t support this.”
Bronchiolitis — most often caused by RSV — is the leading reason why babies are admitted to hospital in the UK during winter. It typically affects babies under one year old and can be especially severe in those born prematurely. While most of the twenty-five thousand babies admitted will recover with oxygen and fluids, around a thousand of the most unwell require intensive care and a ventilator to support their breathing. Currently, there is no other treatment for bronchiolitis, but a vaccine is now being offered to Mum-to-be in the last months of pregnancy.
The BESS trial was designed to give families and clinicians clear answers. It ran over six winter seasons from 2019 to 2024.
Professor Semple added: “While we continue to research better ways to care for these sick babies, I urge Mums-to-be to accept the offer of the RSV vaccine during pregnancy, which will protect their newborn babies from severe bronchiolitis.”
The researchers emphasise that surfactant therapy remains essential for premature newborn babies and advocate for further studies to explore targeted treatments for bronchiolitis.
Ends
Notes to editors
MRC and NIHR
The study was funded by an MRC and NIHR partnership created to support the evaluation of interventions with potential to make a step-change in the promotion of health, treatment of disease and improvement of rehabilitation or long-term care.
The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:
About the MRC
The Medical Research Council is at the forefront of scientific discovery to improve human health. Founded in 1913 to tackle tuberculosis, the MRC now invests taxpayers’ money in some of the best medical research in the world across every area of health. Thirty-three MRC-funded researchers have won Nobel prizes in a wide range of disciplines, and MRC scientists have been behind such diverse discoveries as vitamins, the structure of DNA and the link between smoking and cancer, as well as achievements such as pioneering the use of randomised controlled trials, the invention of MRI scanning, and the development of a group of antibodies used in the making of some of the most successful drugs ever developed. Today, MRC-funded scientists tackle some of the greatest health problems facing humanity in the 21st century, from the rising tide of chronic diseases associated with ageing to the threats posed by rapidly mutating micro-organisms. The Medical Research Council is part of UK Research and Innovation. https://mrc.ukri.org/
END
Funded by a partnership between the UK’s UKRI Medical Research Council (MRC) and National Institute for Health and Care Research (NIHR), and by Chiesi Farmaceutici SpA, Italy, the Bronchiolitis Endotracheal Surfactant Study (BESS) trial is the largest-ever randomised study of surfactant for bronchiolitis.
The results are published today (21 March 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 illness can be especially 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 more easily, the study team set out to determine whether this therapy could also benefit babies hospitalised with bronchiolitis.
The study ran across 15 children’s hospitals in England, Scotland, and Northern Ireland and involved 232 critically ill babies. However, surfactant did not reduce the time they needed to be on a ventilator (life-support breathing machine).
Professor Calum Semple OBE, the study’s lead from the University of Liverpool and Alder Hey Children’s NHS Foundation Trust, said: “The treatment was safe, but it didn’t make any difference to how long babies stayed on ventilators. We had hoped that surfactant might speed up recovery for these very sick babies, but the evidence doesn’t support this.”
Bronchiolitis — most often caused by RSV — is the leading reason why babies are admitted to hospital in the UK during winter. It typically affects babies under one year old and can be especially severe in those born prematurely. While most of the twenty-five thousand babies admitted will recover with oxygen and fluids, around a thousand of the most unwell require intensive care and a ventilator to support their breathing. Currently, there is no other treatment for bronchiolitis, but a vaccine is now being offered to Mum-to-be in the last months of pregnancy.
The BESS trial was designed to give families and clinicians clear answers. It ran over six winter seasons from 2019 to 2024.
Professor Semple added: “While we continue to research better ways to care for these sick babies, I urge Mums-to-be to accept the offer of the RSV vaccine during pregnancy, which will protect their newborn babies from severe bronchiolitis.”
The researchers emphasise that surfactant therapy remains essential for premature newborn babies and advocate for further studies to explore targeted treatments for bronchiolitis.
Ends
Notes to editors
MRC and NIHR
The study was funded by an MRC and NIHR partnership created to support the evaluation of interventions with potential to make a step-change in the promotion of health, treatment of disease and improvement of rehabilitation or long-term care.
The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:
- Funding high quality, timely research that benefits the NHS, public health and social care;
- Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
- Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
- Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
- Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
- Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.
About the MRC
The Medical Research Council is at the forefront of scientific discovery to improve human health. Founded in 1913 to tackle tuberculosis, the MRC now invests taxpayers’ money in some of the best medical research in the world across every area of health. Thirty-three MRC-funded researchers have won Nobel prizes in a wide range of disciplines, and MRC scientists have been behind such diverse discoveries as vitamins, the structure of DNA and the link between smoking and cancer, as well as achievements such as pioneering the use of randomised controlled trials, the invention of MRI scanning, and the development of a group of antibodies used in the making of some of the most successful drugs ever developed. Today, MRC-funded scientists tackle some of the greatest health problems facing humanity in the 21st century, from the rising tide of chronic diseases associated with ageing to the threats posed by rapidly mutating micro-organisms. The Medical Research Council is part of UK Research and Innovation. https://mrc.ukri.org/
END