A Zika virus vaccine of high to moderate efficacy may eliminate prenatal infections, according to research published in the Annals of Internal Medicine.
In order to quantify the effect of Zika vaccine prioritization of females age 9 to 49 followed by males in the same age range on incidence of prenatal infections, a compartmental model of Zika transmission between mosquitoes and humans was developed.
Results of the model indicated that a reduction in prenatal Zika infections by at least 94%, depending on country-specific attack rate factors, is achievable with a base-case vaccine efficacy of 75% and vaccination coverage of 90%, immunizing females age 9 to 49. In areas where Zika outbreaks are not expected for at least 10 years, targeting vaccines to women age 15 to 29 is more efficient than women ≥30.
Investigators concluded that a vaccine, once available and effectively deployed, could reduce prenatal infections. Any reductions, however, would be sensitive to local factors such as demographics, transmission potential and outbreak timing. Several simplifying assumptions were necessary with the modelling approach; therefore not all local and neighborhood-level differences in mosquito abundance and Zika incidence are likely to be captured.
However, these results do “show the substantial effect that Zika vaccination programs could have in mitigating and preventing future outbreaks” and “highlight the importance of targeted Zika vaccination.”
Durham D, Fitzpatrick M, Ndeffo-Mbah M, Parpia A, Michael N, Galvani A. Evaluating vaccination strategies for Zika virus in the Americas [published online April 3, 2018]. Ann Intern Med. doi:10.7326/M17-0641