Dengvaxia, a chimeric
yellow fever tetravalent dengue vaccine developed by SanofiPasteur is widely licensed in
dengue-endemic countries. In a large cohort study
Dengvaxia was found to partially protect children who had prior dengue virus (DENV)
infections but sensitized seronegative children to breakthrough DENV disease of enhanced severity. In 2019, the European Medicines Agency and the US FDA issued licenses that reconciled safety issues by restricting
vaccine to individuals with prior
dengue infections. Using revised
Dengvaxia efficacy and safety data we sought to estimate hospitalized and
severe dengue cases among the more than 800,000 9 year-old children vaccinated in the Philippines. Despite an overall
vaccine efficacy of 69% during 4 years post-vaccination we project there will be more than one thousand vaccinated seronegative and seropositive children hospitalized for
severe dengue. Assisting these children through a program of enhanced surveillance leading to improved care deserves widespread support. Clinical responses observed during breakthrough
dengue infections in vaccinated individuals counsel prudence in design of
vaccine policies. Recommendations concerning continued use of this
dengue vaccine are: (1) obtain a better definition of
vaccine efficacy and safety through enhanced phase 4 surveillance, (2) obtain a valid, accessible, sensitive, specific and affordable serological test that identifies past wild-type dengue virus
infection and (3) clarify safety and efficacy of
Dengvaxia in flavivirus immunes. In the absence of an acceptable serological screening test these unresolved ethical issues suggest
Dengvaxia be given only to those signing informed consent.