RSV is a common virus that causes coughs and colds and can lead to a severe lung infection called bronchiolitis, which can result in babies being admitted to intensive care.
Following the US, the UK introduced year-round maternal RSV vaccination to its routine immunization schedule in late summer 2024- with vaccination recommended as soon as possible after 28 weeks of gestation. At the time of roll-out, real-world effectiveness of the maternal vaccine post-licensure remained unclear.
In the current study, researchers investigated the effectiveness of the maternal RSV vaccine against hospitalization for RSV-associated acute lower respiratory infections in infants. To do so, they analyzed data from 537 mother-infant pairs; the infants from which were hospitalized and diagnosed with bronchiolitis. Tests revealed that a total of 391 infants were RSV-positive, while 146 were RSV-negative.
Ultimately, the researchers found that mothers of babies without RSV were twice as likely to have received the vaccine before delivery than mothers of babies with RSV. Whereas 19% of mothers to babies who were RSV-positive received the vaccine before giving birth, the same was true for 41% of mothers to babies who were RSV-negative.
The researchers also found that receiving the vaccine over 14 days before delivery was more protective, and linked to a 72% reduction in hospital admissions. Infants born to mothers who were vaccinated at any point before giving birth were 58% less likely to be hospitalized.
Experts recommend vaccination as soon as possible from 28 weeks of pregnancy for most protection as this enables more time for mothers to generate and pass antibodies on to their babies.
In their study, the researchers wrote that RSV vaccine campaigns should begin before the start of the RSV season, which typically begins in the fall, peaks in winter and then ends in Spring in the US.
"With the availability of an effective RSV vaccine shown to significantly reduce the risk of hospitalization in young infants in the UK, there is an excellent opportunity for pregnant women to get vaccinated and protect themselves and their infants from RSV bronchiolitis this coming winter," said lead author of the study, Dr Thomas Williams from the University of Edinburgh's Institute for Regeneration and Repair, in a press release.
Sources: Science Daily, The Lancet Child & Adolescent Health