Pfizer’s experimental respiratory syncytial virus (RSV) vaccine, found to be effective in preventing severe infections in infants after being given in a late-stage study to expectant mothers, could be the first maternal vaccine on the market to relieve the burden of disease in young children, if approved.
The company stopped the trial after the early success and plans to file for approval by the end of 2022, reports Reuters.
“Maternal immunisation … protects the infant from day one… which is important because the peak of hospitalisation in these infants due to RSV is around one to two months of age,” said Kena Swanson, vice-president of Viral Vaccines at Pfizer.
The vaccine did not meet the study’s second main goal of preventing less severe respiratory illness, the company said.
Companies such as Pfizer and GSK are racing to develop a vaccine against RSV, a leading cause of pneumonia in toddlers and older adults, and which sees 58 000 children under five being hospitalised in the US annually.
Pfizer’s vaccine candidate met one of the two primary endpoints of the study, showing 81.8% efficacy in preventing a severe form of lower respiratory tract illness in infants in the first 90 days.
Signs of severe illness in the study included very low oxygen levels, being put on a mechanical ventilator, being placed in an intensive care unit, or being unconscious due to RSV. The unmet endpoint was for reduction of illness in the infants that necessitated care by a healthcare provider.
RSV infections among young children are rising in the US: there are currently no approved RSV vaccines.
In August, Pfizer had said its RSV vaccine was effective among older adults in a late-stage study, and in October, rival GSK said its RSV shot was 82.6% effective in a late-stage study, also involving older adults.
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