Population-level effect of potential HSV2 prophylactic vaccines on HIV incidence in sub-Saharan Africa

Abstract

Herpes simplex virus type-2 (HSV2) infection increases HIV transmission. We explore the impact of a potential prophylactic HSV2 vaccination on HIV incidence in Africa using STDSIM an individual-based model. A campaign that achieved 70% coverage over 5 years with a vaccine that reduced susceptibility to HSV2 acquisition and HSV2 reactivation by 75% for 10 years, reduced HIV incidence by 30-40% after 20 years (range 4-66%). Over 20 years, in most scenarios fewer than 100 vaccinations were required to avert one HIV infection. HSV2 vaccines could have a substantial impact on HIV incidence. Intensified efforts are needed to develop an effective HSV2 vaccine.

Fig. 1

Observed (95% CI) and simulated prevalence of HIV and HSV2 by age and gender in 1997 and over time in Cotonou and Kisumu (adults aged 15–49 years). M, male; F, female. Note difference in y-axis scale used on HIV prevalence graphs. Gen. pop. = general population. ANC = ante-natal clinic.

Fig. 2

Impact of HSV2 prophylactic vaccines on HSV2 incidence after 10 and 20 years, by city (adults aged 15–49 years). For each combination of vaccine coverage (50%, 70%, 90%), vaccine duration of effect (5 years, 10 years, lifelong), vaccine effect (susceptibility or reactivation or both), and whether a ‘catch-up’ campaign of 15–29-year olds was simulated in addition to routine annual vaccination of 14-year olds, three scenarios are shown corresponding to the ‘weak’ (30%, ⊥), ‘moderate’ (75%, ♦) and ‘strong’ (90%, ⊤) vaccine efficacy. See Section 2 for full details. M, male; F, female.

Fig. 3

Impact of HSV2 prophylactic vaccines on HIV incidence after 10 and 20 years, by city (adults aged 15–49 years). For each combination of vaccine coverage (50%, 70%, 90%), vaccine duration of effect (5 years, 10 years, lifelong), vaccine effect (susceptibility or reactivation or both), and whether a ‘catch-up’ campaign of 15–29-year olds was simulated in addition to routine annual vaccination of 14-year olds, three scenarios are shown corresponding to the ‘weak’ (30%, ⊥), ‘moderate’ (75%, ♦) and ‘strong’ (90%, ⊤) vaccine efficacy. See Section 2 for full details. M, male; F, female.

Fig. 4

Number of vaccinations per HIV infection averted over 10 and 20 years, by city (all ages). The modelled scenario assumes an increase from 0% to 70% vaccine coverage over 5 years in 14–29-year olds using a vaccine with 10-year duration of effect on susceptibility and reactivation in males and females. Three scenarios are shown corresponding to the ‘weak’ (30%, ⊤), ‘moderate’ (75%, ♦) and ‘strong’ (90%, ⊥) vaccine efficacy. See Section 2 for full details.