FDA Briefing Document: Vaccines and Related Biological Products Advisory Committee Meeting

“8.4. Unknown Risks/Data Gaps... Vaccine-enhanced disease - Available data do not indicate a risk of vaccine-enhanced disease, and conversely suggest effectiveness against severe disease within the available follow-up period. However, risk of vaccine-enhanced disease over time, potentially associated with waning immunity, remains unknown and needs to be evaluated further in ongoing clinical trials and in observational studies that could be conducted following authorization and/or licensure.”