Injection | Dr PS Sahana Kadamtala Howrah via Photopin
Vaccines protect us from serious illnesses like mumps, polio and rubella. These diseases, which used to be harmful, are today are no longer a threat in situations where child vaccinations are routine. However, an HIV vaccine remains elusive. The Desmond Tutu HIV Foundation (DTHF) is conducting HIV vaccine trials in the hope that one day we will have an effective HIV vaccine to prevent HIV infection.
The arrival of an HIV vaccine would be a critical turning point in the history of the virus. South Africa has a high HIV burden: nearly 20% of adults are HIV positive. Whilst prevention tools and treatment are available and effective, a vaccine would be a game changer in reducing new HIV infections.
The DTHF is a site for the latest vaccine trial, HTVN 702, which will assess the safety and efficacy of a preventative HIV vaccine among South African adults. The study began in 2016 and is predicted to run for approximately five years. The vaccine is designed to protect HIV-negative people by enabling them to resist infection if they ever come in contact with the virus. Each patient receives a series of injections at five different time points. These include DNA vaccines that rallies the body’s defences against the virus, and injections where a protein is added that gives the immune system an extra boost.
At the end of the trial, the success of the vaccine will be evaluated based on the number of new HIV infections in two different cohorts, comparing patients who received the working vaccine and the placebo.
HIV is especially tricky for the human immune system to eliminate. Each time the virus replicates, it changes slightly. Additionally, the virus hides inside the cells designed to fight it (the immune cells). The HIV vaccine introduces antibodies to the bloodstream that can ‘see past’ HIV’s disguise and neutralise it.
Explanation on why an HIV vaccine is difficult to produce | NIAID
There has only been one HIV vaccine trial that has shown some efficacy so far; a Thai study, RV144, which started in 2003. This trial gave patients a series of HIV vaccines then tested the rates of HIV around three years later. The rate of HIV in the volunteers who received the vaccine was 31% lower than those who received the placebo. The Thai study used a vaccine designed to combat Clade B type HIV; however, in South Africa the epidemic is dominated by Clade C type virus. South African scientists have adapted the Thai RV144 virus to target Clade C. This is the vaccine that will be administered in the current HVTN 702 trial.
Dr Danielle Crida, senior medical officer of the DTHF, commented on the undergoing trial. “We are following by giving a boost at 12 months, so we are hoping that it will be more effective than the Thai vaccine.” Crida hopes that the extra ‘boost’ will increase the efficacy of the Southern African vaccine. She also noted that “We are aiming for a 50-60% efficacy.” If this can be achieved, it would be a huge advancement in the fight against HIV.
