• David P Durham, Meagan C Fitzpatrick, Martial L Ndeffo-Mbah, Alyssa S Parpia, Nelson L Michael, and Alison P Galvani.
• Center for Infectious Disease Modeling and Analysis, Yale School of Public Health, New Haven, Connecticut (D.P.D., M.L.N., A.S.P., A.P.G.).
• Ann. Intern. Med. 2018 May 1; 168 (9): 621630621-630.

BackgroundMosquito-borne and sexually transmitted Zika virus has become widespread across Central and South America and the Caribbean. Many Zika vaccine candidates are under active development.ObjectiveTo quantify the effect of Zika vaccine prioritization of females aged 9 to 49 years, followed by males aged 9 to 49 years, on incidence of prenatal Zika infections.DesignA compartmental model of Zika transmission between mosquitoes and humans was developed and calibrated to empirical estimates of country-specific mosquito density. Mosquitoes were stratified into susceptible, exposed, and infected groups; humans were stratified into susceptible, exposed, infected, recovered, and vaccinated groups. Age-specific fertility rates, Zika sexual transmission, and country-specific demographics were incorporated.Setting34 countries and territories in the Americas with documented Zika outbreaks.Target PopulationMales and females aged 9 to 49 years.InterventionAge- and sex-targeted immunization using a Zika vaccine with 75% efficacy.MeasurementsAnnual prenatal Zika infections.ResultsFor a base-case vaccine efficacy of 75% and vaccination coverage of 90%, immunizing females aged 9 to 49 years (the World Health Organization target population) would reduce the incidence of prenatal infections by at least 94%, depending on the country-specific Zika attack rate. In regions where an outbreak is not expected for at least 10 years, vaccination of women aged 15 to 29 years is more efficient than that of women aged 30 years or older.LimitationPopulation-level modeling may not capture all local and neighborhood-level heterogeneity in mosquito abundance or Zika incidence.ConclusionA Zika vaccine of moderate to high efficacy may virtually eliminate prenatal infections through a combination of direct protection and transmission reduction. Efficiency of age-specific targeting of Zika vaccination depends on the timing of future outbreaks.Primary Funding SourceNational Institutes of Health.

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