A nationwide prospective cohort study on safety of the 17D-204 yellow fever vaccine during a vaccine shortage in Japan

In response to the vaccine shortage of yellow fever vaccine (YF-VAX) due to manufacturing delays, the unapproved 17D-204 YF-VAX was used as an investigator-initiated clinical trial in Japan. The vaccine was administered to 11 279 participants in 19 YF vaccination centres in Japan, and few serious adverse events were observed.