HIV Vaccine Tested in Thailand now Offers Some Hope in South African Study

Sep 22, 2019 | AIDS, HIV, South African Medical Research Council, Vaccine

An experimental vaccine called RV144 was initially tested in Thailand with modest impact has shown more promise in a South African study. The study was published in the peer-reviewed journal Science Translational Medicine Journal under the leadership of Professor Glenda Gray, president of the South African Medical Research Council as reported in the Citizen in South Africa.

What is RV144?

The RV144 program has been sponsored by the United States Military HIV Research Program (MHRP). Most recently an EV144 study was sponsored by the U.S. Army and conducted by the Thailand Ministry of Public Health. MHRP provided overall project leadership, provided overall project leadership, and the Armed Forces Research Institute of Medical Sciences (AFRIMS) helped execute the trial.

Follow up Research

MHRP began a small clinical study, RV305, in April 2012 in Thailand to evaluate re-boosting in volunteers who participated in the RV144 study. The results were published in 2017 and shows that boosting RV144 volunteers 6-8 years later with ADISVAX B/E vaccine resulted in higher immune responses that were seen immediately after RV144. Another clinical study, RV306, began in September 2013 using the RV144 vaccine regimen to compare additional vaccine boosts and gather more immunogenicity data in 360 volunteers.

The South Africa Program

The Pox-Protein Public-Private Partnership (P5) represents a public-private collaborative team that initiated a follow-up program using a similar vaccine regimen in Southern Africa and initiated Phase I clinical trials by early 2015. The research program seeks to bolster protection from the virus by adding an extra vaccine boost and better adjuvants in the South African studies. 

The new work, based on the first HIV vaccine trials a decade ago, showed promise but wasn’t good enough for production. The investigators learned that the vaccine’s efficacy diminished if booster vaccines were not included (booster does is an extra administration of the vaccine after the preliminary dose—it effectively enhances the effect of the vaccine).

The study included 100 men and women between the ages of 18 and 40 from Cape Town, Kerksdrop and Soweto. This time the participants were given the booster shots and were followed longer than a year. The first goal of the study was to not determine the participants’ immune system response to the vaccine.


There are different subtypes of HIV known as clades (e.g. subtypes). The vaccine was designed for the Thailand clades, where the predominant ones are known as B and E. In South Africa the dominant clades are C. Despite this the investigators did not change the vaccine to tailor it to the South African clade.

South African Participant Immune Response

To the surprise of the investigative team, the participant population in South Africa experienced stronger immune responses than the Thai population—a bigger surprise because the clades in Thailand and South Africa are different.

Challenges with HIV Vaccines

The types of HIV circulating locally not to mention genetic factors can influence the immune response in a study. Regional differences in elements such as clades raise the possibility that different regions of the world may require separate types of HIV vaccine based on the local circulating strain.

Investigator Comments

Professor Glenda Gray, president of the South African Medical Research Council notes that “No one has been cured naturally, so we operate in the dark. We play catch-up the whole time. So we look at the parts of the virus which do not change the whole time and try to focus on that.”

HIV Crisis Continues

Improvements aside in HIV prevention, approximately 1.8 million people contract HIV in 2018 alone reported a press statement by the HIV Vaccine Trials Network. In South Africa, 220,000 people are estimated to have contracted HIV last year reports the country’s main AIDS model, however, the number of infections is declining.

Lead Research/Investigator

Professor Glenda Gray, President of the South African Medical Research Council