Almost 40 years after the discovery that HIV causes AIDS and 36 years after the first attempt to create a vaccine against the virus, there is still no working vaccine. Although Acquired Immunodeficiency Syndrome is no longer a death sentence, doctors are keen to create a medicine that will make HIV largely disappear.

Experts hope that the PrEPVacc trial, symbolically called "the last roll of the dice", will bring positive results and eventually a working vaccine.

As we can read on cnn.com, only one clinical trial from 2009 showed modest effectiveness at preventing HIV infection. The efficacy of the vaccine from that time was around 30%. Experts emphasise that each of the two new vaccines being tested at the moment will need to achieve an efficacy of at least 70% in order to be deemed successful.

CNN reports that one vaccine combines fragments of synthetic HIV DNA with a protein base, while the other combines DNA, MVA (a weakened smallpox virus) and a protein base.

"This is an evolution, not a revolution. These are both regimens that have never gone into efficacy study before. These vaccines are the best that medical science can currently provide," said Jonathan Weber, lead applicant and coordinator of PrEPVacc and director of the Imperial College Academic Health Science Centre in an interview with cnn.com .

Volunteers to take part in the vaccine trial began to be sought in December 2020. In March 2023, the last of its 1,513 participants were registered. All of them come from South Africa, Uganda and Tanzania and are aged between 18 and 40 years. It was decided to study people from the aforementioned countries because they have very high rates of AIDS among adults.

"These countries already have experience doing HIV prevention studies, not only vaccine trials, have established very good connections with the communities, and have the infrastructure we require," said PrEPVacc trial director Eugene Ruzagira.

As reported by cnn.com, each study participant receives four injections of either vaccine A or B or a saline placebo over 48-week schedule. They also get a special series of PrEP injections taken daily until week 26. This is when immunity is expected to peak. The US Centers for Disease Control and Prevention reports that PrEP, taken regularly and as prescribed, reduces the risk of contracting HIV through sex by approximately 99%, and among people injecting drugs by at least 74%.

After 26 weeks, trial participants are given the option to access the tested vaccine from public health facilities. Unfortunately, it appears that not everyone is switching to long-term use of the drug, also due to shortages in pharmacies.

Research on the vaccine will continue until 2024. Doctors report that at the Verulam research centre, more than half of the participants have already received all the injections. Project members are regularly tested and have daily access to specialists.

If the tested vaccines prove to be effective, further research will be needed and will most likely involve multiple international partners. If, on the other hand, the discovery of an HIV preparation fails, it will be necessary to start all over again.

"In this decade, it will be the last roll of the dice. My prediction is there won’t be another efficacy study of an HIV vaccine until the 2030s," Jonathan Weber said.

Source: cnn.com