FDA Pushes RSV Vaccines for Kids Despite Halted Moderna Trials
Advisers to the FDA recently met to discuss the future of respiratory syncytial virus (RSV) vaccines for children. This followed Moderna’s forced halt of its mRNA RSV vaccine trials after alarming data showed higher rates of severe RSV in vaccinated infants compared to those given a placebo. Clinical trial data revealed 12.5% of vaccinated children developed severe RSV disease, compared to just 5% in the placebo group.
These outcomes raised alarms due to past experiences with RSV vaccines. In the 1960s, trials of a formalin-inactivated RSV vaccine led to vaccine-associated enhanced respiratory disease (VAERD), where vaccination worsened illness instead of preventing it. That trial resulted in two toddler deaths and hospitalization for 80% of the vaccinated participants. Despite decades of research, the risks tied to VAERD remain unresolved.
FDA advisers emphasized the “unmet need” for pediatric RSV vaccines, framing RSV as a leading cause of infant hospitalizations in the US annually. Vaccine makers, spurred by a projected $13.59 billion global RSV vaccine market by 2030, are developing 26 RSV vaccines or monoclonal antibodies for all age groups.
An FDA representative said the Centers for Disease Control and Prevention (CDC) estimates that RSV causes 100-200 infant deaths annually. However, internist Dr. Meryl Nass argued these numbers are overstated. Citing a CDC study analyzing RSV deaths in infants from 2005 to 2016, Nass highlighted that there were 314 deaths in children under age 1 during that period, averaging 25 per year. Only 17 of those deaths listed RSV as the direct cause, raising questions about the urgency for widespread vaccination.
The FDA explored the potential for sequential administration of RSV monoclonal antibodies and vaccines for infants and toddlers. This approach would begin with monoclonal antibodies or maternal vaccination to provide “passive immunity” — ready-made antibodies to fight RSV. Later, a two- or three-shot course of RSV vaccines would aim to develop “active immunity,” enabling the child’s own immune system to combat the virus in subsequent seasons.
While committee members saw potential in sequential administration, they acknowledged insufficient safety data, fueling concerns that industry profits are being prioritized over child safety.
For more details, rand to watch the full FDA advisory meeting click here.
