Elowyn’s mother, Molly, said she is grateful to Harry and the other trialists because “if they didn’t happen then we wouldn’t have had the chance to give her (Elowyn) the extra protection”.
A jab that can be given to pregnant women was introduced last year but it doesn’t cover some babies who are born prematurely.
Nine out of 10 children will get RSV before the age of two, but in most cases it is not diagnosed as the symptoms present as a cough or a cold.
The trial was supported by the National Institute for Health and Care Research (NIHR) and now Nirsevimab – which offers six months’ protection in a single dose – will replace monthly injections of palivizumab, previously offered to a smaller number of vulnerable babies.
According to clinical trial data, external, palivizumab provides about 55% protection while Nirsevimab offers more than 80% protection against the virus.
“We know that preterm babies are a particularly vulnerable group” said Dr Paulson, who works at University Hospital Southampton.
“They’ve got underdeveloped lungs, they’ve got immature immune systems, both of which make them particularly susceptible to really severe infections.”