How low can you go: the impact of a modestly effective HIV vaccine compared with male circumcision.

OBJECTIVE

The first evidence of modest effectiveness of an HIV vaccine was demonstrated by the RV144 trial in Thailand in 2009. Although promising, this vaccine has largely been dismissed because it only had 30% efficacy. In contrast, male circumcision is widely supported and has approximately twice the efficacy, but can only be targeted to half of the population. We question the vaccine efficacy required before being considered in prevention strategies.

DESIGN

We forecast the expected population-level impact of implementing circumcision among males compared with a 30% effective vaccine among males and females.

METHODS

A mathematical transmission model was developed to describe the HIV epidemics in two different settings, Thailand and South Africa, and to forecast the expected impact of circumcision or vaccine interventions.

RESULTS

Interventions using a vaccine with 30% efficacy would likely have a greater population benefit than male circumcision because a proportion of males are already circumcised, thus diminishing the potential target population. Both males and females will receive considerable benefit from vaccination (for example, 33% of infections averted for males and 36% for females in South Africa), whereas females will receive only moderate benefit from male circumcision (for example, 47% of infections averted for males and 19% for females in South Africa). In both settings, it would likely take a number of years before the interventions could have a noticeable impact on HIV epidemics.

CONCLUSION

A moderately effective vaccine, such as the one demonstrated in the RV144 trial, may have a potential role in public health programs.