ENGLAND — A UK Health Security Agency study of nearly 300,000 births in England found that a vaccine given during pregnancy reduced hospital admissions of babies for chest infections caused by respiratory syncytial virus by more than 80%. The study followed babies born between September 2024 and March 2025, equivalent to about 90% of all births during that time.

More than 4,500 babies were admitted to hospital with respiratory syncytial virus during the study period, with the vast majority born to mothers who had not been vaccinated. When the vaccine is given at least four weeks before birth, it is nearly 85% effective at protecting babies from the virus, though it provides some protection even if given less than four weeks before birth. A two-week interval between vaccination and birth can provide protection for babies born early.

Respiratory syncytial virus is one of the main reasons young babies are admitted to hospital before the age of one, and half of newborns catch it. More than 20,000 babies end up seriously ill in hospital in the UK every year due to the virus, which can cause anything from a mild cold to a life-threatening chest infection because of inflammation in the lungs. Small numbers of babies die from it every year.

Since 2024, women in the UK have been offered the vaccine from 28 weeks of pregnancy, after clinical trials showed it could boost a pregnant woman's immune system enough to pass protection to the baby through the placenta. Babies born to vaccinated pregnant women are protected from birth.

"This is very, very frightening as a parent, frightening with good reason." said Dr Conall Watson, national programme lead for RSV at the UK Health Security Agency. He added: "Get it on time. But if you can't, do get vaccinated all the way through the third trimester."

Around 64% of pregnant women in England have received the RSV vaccine, compared with around 53% in London. The flu and whooping cough vaccines are also recommended during pregnancy, and adults aged 75 or over, or residents of care homes for older adults, are offered the RSV vaccine across the UK.

Laine Lewis described how her son Malachi developed a cold as a baby that deteriorated into respiratory syncytial virus and required oxygen support. Malachi was taken to Bristol Children's Hospital after he stopped breathing, and a scan soon after revealed that he had brain damage. "I'd encourage people to take the vaccine for RSV because it will help their child," Lewis said.