RSV usually causes coughs and colds, but can make some children very ill with breathing problems, pneumonia and a lung infection called bronchiolitis.
According to NHS England, premature babies are three times more likely to go to hospital with RSV and are 10 times more likely to need intensive care compared with full-term babies.
Every year around 30,000 children in the UK aged under five need hospital care because of the virus, and around 30 don’t survive.
The drug offers six months’ protection in a single dose, and is more than 80% effective.
Neo-natal clinics will deliver the injection to premature babies. Families of vulnerable infants with heart or lung conditions or weakened immune systems will be advised by their medical teams how to get the jab before this winter.
“It will offer a long-lasting defence, helping to avoid unnecessary hospitalisations and serious illness, giving babies the best possible start in life and shielding them from harm,” said Dr Claire Fuller, co-national medical director for NHS England.