Hopes for an effective vaccine against HIV have been dashed again after the Phase 2b/3 study, named HVTN 702 or Uhambo that was conducted in South Africa had to be stopped after no evidence of efficacy could be found.

According to Medical Research Council president Prof Glenda Gray who led the study this is a huge disappointment as years of study went into the development of the trial vaccine. The $104 million trail was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health in die US.

The HVTN 702 study enrolled 5407 HIV-negative volunteers at 14 sites across South Africa. The study population consisted of sexually active men and women aged 18 to 35 years. The study volunteers were randomly assigned to receive either the investigational vaccine regimen or placebo injections. Study participants received six injections over 18 months. As with all NIAID-sponsored HIV prevention trials, the safety of HVTN 702 study participants was closely monitored throughout the trial, and participants were offered the local standard of care for preventing HIV, including access to oral pre-exposure prophylaxis (PrEP).

The trial tested an investigational prime-boost vaccine regimen based on the only vaccine regimen ever to show protection from HIV—the regimen tested in the RV144 clinical trial in Thailand led by the U.S. Military HIV Research Program and the Thai Ministry of Health. For HVTN 702, the vaccine regimen was adapted to the HIV subtype Clade C most common in southern Africa, where the pandemic is most pervasive. 

NIAID says the decision to abandon the trial is based on data of the January 23, 2020 interim analysis that examined data from 2694 volunteers who received the investigational vaccine regimen and 2689 volunteers who received the placebo injection. The analysis looked at how many participants were diagnosed with HIV after at least 60% of the participants had been in the study for more than 18 months — enough time for the vaccine regimen to stimulate an immune response. In this analysis, 129 HIV infections occurred among the vaccine recipients, and 123 HIV infections occurred among the placebo recipients.

Based on these findings, the Data and Safety Monitoring Board (DSMB) concluded that the investigational vaccines had not shown any efficacy. The DSMB recommended that no further vaccinations be administered and that participants remain in the study for follow-up. The report noted there was no significant evidence of either decreased or increased infection rates with vaccination. 

“An HIV vaccine is essential to end the global pandemic, and we hoped this vaccine candidate would work. Regrettably, it does not,” said NIAID Director Anthony Fauci. “Research continues on other approaches to a safe and effective HIV vaccine, which I still believe can be achieved.”

“The people of South Africa have made history by answering this important scientific question. Sadly, we wish the answer was different,” said Prof Gray.  “We will continue to explore promising avenues for preventing HIV with other vaccines and tools, both in South Africa and around the world.

Source: https://www.nih.gov/news-events/news-releases/experimental-hiv-vaccine-regimen-ineffective-preventing-hiv