Predicting the level of vaccine-induced cross-immunity necessary to eliminate HIV epidemics composed of multiple subtypes.

In a very interesting study, Kiwanuka et al. [1] report significant differences in the rates of transmission associated with different HIV-1 subtypes in Rakai, Uganda. Controlling for other factors, they find the transmission rate of subtype A to be nearly double that of subtype D. The authors suggest that differential transmission rates among subtypes are important for: (i) HIV vaccine development and testing, (ii) understanding the dynamics of HIV-1 epidemics in different geographical regions and (iii) projections of the pandemic.