HIV Epidemic in Asia: Implications for HIV Vaccine and Other Prevention Trials

Abstract

An overall decrease of HIV prevalence is now observed in several key Asian countries due to effective prevention programs. The decrease in HIV prevalence and incidence may further improve with the scale-up of combination prevention interventions. The implementation of future prevention trials then faces important challenges. The opportunity to identify heterosexual populations at high risk such as female sex workers may rapidly wane. With unabating HIV epidemics among men who have sex with men (MSM) and transgender (TG) populations, an effective vaccine would likely be the only option to turn the epidemic. It is more likely that efficacy trials will occur among MSM and TG because their higher HIV incidence permits smaller and less costly trials. The constantly evolving patterns of HIV-1 diversity in the region suggest close monitoring of the molecular HIV epidemic in potential target populations for HIV vaccine efficacy trials. CRF01_AE remains predominant in southeast Asian countries and MSM populations in China. This relatively steady pattern is conducive to regional efficacy trials, and as efficacy warrants, to regional licensure. While vaccines inducing nonneutralizing antibodies have promise against HIV acquisition, vaccines designed to induce broadly neutralizing antibodies and cell-mediated immune responses of greater breadth and depth in the mucosal compartments should be considered for testing in MSM and TG. The rationale and design of efficacy trials of combination prevention modalities such as HIV vaccine and preexposure prophylaxis (PrEP) remain hypothetical, require high adherence to PrEP, are more costly, and present new regulatory challenges. The prioritization of prevention interventions should be driven by the HIV epidemic and decided by the country-specific health and regulatory authorities. Modeling the impact and cost-benefit may help this decision process.

FIG. 1.

HIV epidemic in Asia and the Pacific, 2013. Proportion by country of people living with HIV and of new HIV infections. UNAIDS Gap Report 2014.

FIG. 2.

HIV-1 molecular epidemiology in Asia. Partial and full genome of HIV-1 sequences obtained from the Los Alamos National Laboratory HIV database (www.hiv.lanl.gov) and the U.S. Military HIV Research Program (MHRP); HIV-1 subtyping data from the MHRP (personal communication, unpublished data) were used to compile circulating subtype distributions by country. (A) Geographic and temporal distribution of circulating HIV-1 subtypes by country for 2000–2007 and 2008–2014. (B) Relative percentage changes in HIV-1 subtype prevalence for selected countries and subtypes from 2000–2007 to 2008–2014. Bangladesh, Myanmar, Mongolia, Macau, Nepal, and Philippines are omitted due to insufficient data.

FIG. 3.

Proportion of new HIV infections by mode of transmission, Thailand, 1985–2030. Thailand Working Group on HIV/AIDS Projection.

FIG. 4.

Geographic distribution of cumulative HIV/AIDS cases in China. China AIDS Response Progress Report, Ministry of Health of the People's Republic of China, UNAIDS, 2012.

FIG. 5.

HIV prevalence and incidence in men who have sex with men (MSM) and people who inject drugs (PWID), India, 2012–2013. The MSM study was conducted in 12 cities and the PWID study was conducted in 15 cities.