A Zika virus vaccine of moderate to high efficacy may virtually eliminate prenatal infections through a combination of direct protection and transmission reduction, a recent study found. The study sought to quantify the effect of Zika vaccine (with 75% efficacy) prioritization of females aged 9 to 49 years, followed by males aged 9 to 49 years, on incidence of prenatal Zika infections. A compartmental model of Zika transmission between mosquitoes and humans was developed and calibrated to empirical estimates of country-specific mosquito density. 34 counties and territories in the Americans with documented Zika outbreaks were included in the analysis. Researchers found:
- For a base-case vaccine efficacy of 75% and vaccination coverage of 90%, immunizing females aged 9 to 49 years would reduce the incidence of prenatal infections by at least 94%.
- In regions where an outbreak is not expected for at least 10 years, vaccination of women aged 15 to 29 years in more efficient than that of women aged ≥30 years.
- The study was limited in that population-level modeling may not capture all local and neighborhood-level heterogeneity in mosquito abundance or Zika incidence.
Durham DP, Fitzpatrick MC, Ndeffo-Mbah ML, Parpia AS, Michael NL, Galvani AP. Evaluating vaccination strategies for Zika virus in the Americas. [Published online ahead of print April 3, 2018]. Ann Intern Med. doi:10.7326/M17-0641.