An update to the US National Institutes of Health Clinical Trial registry reports that Moderna’s experimental HIV vaccine will begin human trials as early as today (19th of August). Moderna was among the first to develop a vaccine to COVID-19 in 2020. It is hoped that its mRNA technology will once again help in fighting one of science’s most challenging viruses.

The phase 1 trial expected to run until May 2023 will recruit 56 healthy participants between the ages of 18 and 50. Four groups will participate in the trial, with two groups receiving a mix of the two versions of the vaccine and the two others receiving just one. The trial will evaluate the safety of the vaccine and its efficacy in producing a range of neutralizing antibodies against HIV.

If the vaccines passes this phase they will still need to pass through phase 2 and 3 trials to determine their efficacy in a greater population.

The two versions of the vaccine developed by Moderna, mRNA-1644 and mRNA-1644v2-core aim to combat the challenges faced by previous attempts to tackle the virus. HIV lingers in the body for years before developing into AIDS. In this time the virus frequently mutates, becoming almost unrecognisable to antibodies.

The vaccines in question induce broadly neutralizing antibodies at levels not reported in previous vaccines. These antibodies target numerous HIV variants and neutralize parts of the virus that are changed minimally by mutation.

Albeit such mRNA technology was successful in generating high levels of antibodies against COVID-19, experts have emphasized that vaccinating against HIV will not be as straightforward. Ultimately it is believed that multiple vaccines will be required to elicit a sufficient immune response to protect against HIV, which is considerably more effective in avoiding the body’s defences than COVID-19.

Immunologist at Imperial College London, Robin Shattock, described the movement of Moderna’s HIV vaccine to human trials as “exciting” and “a potential first step forward on a very long journey”.

“Moderna are testing a complicated concept which starts the immune response against HIV. It gets you to first base but it’s not a home run. Essentially we recognise that you need a series of vaccines to induce a response that gives you the breadth needed to neutralise HIV.

“It’s quite likely that their technology may allow them to start to look at that process, but we’re a very long way away from an effective vaccine.”

Moderna’s endeavours to create a HIV vaccine are a part of the international Aids Vaccine Initiative and the Bill and Melinda Gates Foundation. Today 38 million people are living with HIV while two million new infections are reported each year.