A Functional Vaccine Against HIV: Lenacapavir Demands A New Prevention Infrastructure Steven N. Leonard April 16, 2026

https://www.healthaffairs.org/content/forefront/functional-vaccine-against-hiv-lenacapavir-demands-new-prevention-infrastructure When the results of the PURPOSE 1 and PURPOSE 2 trials were published in the New England Journal of Medicine in 2024, I felt something I had not expected to feel about HIV in my lifetime: genuine awe—not at progress but at the possibility of an end. PURPOSE 1 reported zero infections. Not fewer infections. Zero, among more than 2,100 women receiving twice-yearly subcutaneous injections of lenacapavir. PURPOSE 2 confirmed it across a broader, more diverse global population: a 96 percent reduction in HIV incidence, with superiority over daily oral PrEP. Taken together, 100 percent efficacy in one trial and 96 percent in another.