A maternal respiratory syncytial virus (RSV) vaccine candidate prevents infections in infants and comes with “generally favorable” safety data, said FDA staff in briefing documents released ahead of an advisory committee meeting this week, but the reviewers “noted potential uncertainty based on the numerical imbalance in premature deliveries.”
On Thursday, members of the Vaccines and Related Biological Products Advisory Committeeo (VRBPAC) will weigh in on whether the available data support the safety and efficacy of Pfizer’s RSV prefusion F protein vaccine when given to mothers in the second or third trimester of pregnancy for preventing RSV-related lower respiratory tract illness in infants, including severe cases.
The FDA recently approved the first-ever RSV vaccine for older adults, but no vaccine exists for protecting infants, a particularly vulnerable group. A prior effort at developing a formalin-inactivated RSV vaccine in the late 1960s failed when vaccinated infants developed enhanced respiratory disease following their first infection.
RSV infections make up the bulk of lower respiratory tract infections in infants, with hospitalization rates ranging from 1% to 3%, and peaking in early infancy, according to the briefing documents. Mortality rates for hospitalized infants range from 1% to 3% as well.
“Risk factors for severe disease include prematurity, underlying chronic lung or heart disease, and immunodeficiency; however, healthy infants 0 to 6 months of age are also at significant risk for morbidity and mortality,” wrote agency staff.