The seventh major HIV vaccine efficacy trial will begin enrollment in southern Africa in November, aidsmap reports. The Phase IIb/III HVTN 702 trial was first announced in May. Initial, encouraging findings of a pilot study, HVTN 100, of the vaccine were recently presented at the 21st International AIDS Conference in Durban, South Africa (AIDS 2016).

The vaccine under investigation is a retooled version of the one that in 2009 was associated with a 31 percent reduction in HIV risk, compared with a placebo, in the RV144 vaccine study, conducted in Thailand. That risk reduction applied to the 3.5-year period of the study, whereas during the first year the vaccine reduced HIV risk by 60 percent. (In other words, the vaccine’s protection was initially substantial but was not durable.)

The HVTN 702 trial will enroll approximately 5,400 men and women 18 to 34 years old who are at risk of contracting HIV. At least 40 percent of the participants will be male and at least 40 percent will be female.

The RV144 vaccine was modified for this new trial to apply to HIV subtype C, which is predominant in southern Africa, rather than subtypes B and E, which are the most prevalent in Thailand. The researchers do not know whether the retooled vaccine, if effective, will also work for other subtypes.

The ongoing HVTN 100 vaccine trial, which is being conducted at five sites in South Africa, is using a “prime-boost” method. It begins with two shots, given a month apart, of a prime vaccine and continues with one shot each of the prime and the boost components at months three, six and 12. A total of 210 people have received the vaccine; 42 received a placebo.

The results of HVTN 100 presented at AIDS 2016 concern the first 6.5 months of the study, so participants have not yet received the 12-month shot. The vaccine has met various criteria that show it stimulates the immune system and justify the launch of the more advanced trial, HVTN 702.

To read the aidsmap article, click here.

To read the conference abstract, click here.

To download the presentation slides, click here.