Large phase 3 HIV vaccine study in south Africa is stopped early due to lack of efficacy

Simon Collins, HIV i-Base

On 3 February, the US National Institute for AIDS and Immune Disorders (NIAID) issued a press release about the early stopping of a large HIV vaccine study due to lack of efficacy. [1]

Since 2015, the phase 3 HVTN 702 (Uhambo) study had randomised 5407 HIV negative volunteers to either receive a prime-boost vaccination adapted for HIV clade C or a matched placebo injection, with six injections planned over 18 months. The study was being run in 14 sites in South Africa.

The vaccine regimen included of two experimental vaccines: a canarypox vector-based vaccine called ALVAC-HIV and a two-component gp120 protein subunit vaccine with an adjuvant to enhance the body’s immune response to the vaccine (both modified from those found to have a modest effect in the Thai RV144 vaccine study). 

On 23 January 2020, an interim analysis by the studies independent Data and Safety Monitoring Board (DSMB) reported 129 vs 123 HIV new infections in the vaccine vs placebo recipients, and recommended that the study be closed early.

NIAID followed the DSMB recommendation and has stopped any further injections, although safety follow-up with continue.


Although this is disappointing news, several other large HIV prevention studies are ongoing.

These include the phase 3 Imbokodo and Mosaico studies using a mosaic vaccine developed by Janssen (results due 2022) and the AMP studies using the bNAb VRC01 (results due end 2020).

The press statement also noted that participants in HVTN 702 were able to use daily PrEP (as this is currently standard of care in South Africa), although this has not been allowed for Imbokodo and Mosaico or in the South African VRC01 study.


  1. NIAID press release. Experimental HIV vaccine regimen ineffective in preventing HIV. (03 February 2020).
  2. NIH press statement. NIH and partners launch HIV vaccine efficacy study. (30 November 2017).
  3. NIH press statement. NIH and partners to launch HIV vaccine efficacy trial in the Americas and Europe. (15 July 2019).
  4. NIH launches large clinical trials of antibody-based HIV prevention. (7 April 2016).

Links to other websites are current at date of posting but not maintained.