The Lancet last Friday published the 52-week results of APPROACH, an HIV vaccine whose 28-week results, reported by aidsmap.com last year, were sufficiently impressive for it to be taken forward into a human efficacy trial among 2600 young women in southern Africa.
These latest results provided more details of the immune responses to the vaccine, which is already being taken forward into the phase 2b efficacy trial, the Imbokodo or HVTN705 trial (this is the second efficacy trial now to be happening: the HVTN 702 trial started at the end of 2016).
What has excited special interest with APPROACH is that a parallel trial conducted in rhesus monkeys, with a vaccine designed to closely mimic the human one, and which produced immune responses similar to those in humans, protected two-thirds (67%) of monkeys challenged with six rectal doses of a highly pathogenic Simian Immunodeficiency Virus analogous to HIV. The efficacy against each single challenge was 94%.
It’s important to emphasise that the immune responses produced by both the human and the monkey vaccines tailed off over time (though somewhat more slowly in humans) and that we do not know how long the immunity produced by this vaccine, which requires four doses spaced over a year, may last. Previous vaccine concepts have produced promising results in animals but have failed in humans. But the APPROACH study at least suggests that we are getting nearer to having a vaccine with useful efficacy.