Wednesday May 18 was World Aids Vaccine Day 2022, which has been marked every year since 1998 to raise awareness of the ongoing fight for a vaccine against the disease.
Of course, HIV treatments have advanced tremendously over the years, and those who have access to the right treatment can live a normal lifespan.
However, across most of the world, these treatments are either not available or only available to a few - which makes the effort to develop a vaccine all the more important.
Since HIV was first documented in 1983, an estimated 36.3 million people around the world have died of Aids. But why are we still waiting for an effective vaccine to emerge?
Why isn't there a vaccine against Aids yet?
The US government in 1984 predicted that a vaccine for HIV would be available within just two years. But nearly four decades later, there is - as yet - no sign of one.
Scientists succeeded in developing a vaccine against the coronavirus in less than a year, and despite subsequent mutations of the virus, vaccines remain highly effective against severe illness and death from Covid-19.
But experts say that developing a vaccine for HIV is a very different proposition.
One important reason why an effective vaccine against HIV hasn’t yet been developed is the sheer complexity of the virus itself, and its tendency to mutate rapidly.
Writing for The Conversation , Ronald C. Desrosiers - professor of pathology at the University of Miami Miller School of Medicine - explained that the “biological properties that HIV has evolved make development of a successful vaccine very, very difficult”.
The virus has “an ability to generate and to tolerate many mutations in its genetic information”, he noted, adding that there was “an enormous amount of variation among strains of the virus not only from one individual to another but even within a single individual”.
“Everyone knows that people need to get revaccinated against influenza virus each season because of season-to-season variability in the influenza strain that is circulating,” he wrote.
“Well, the variability of HIV within a single infected individual exceeds the entire worldwide sequence variability in the influenza virus during an entire season.”
Dr Desrosiers added that HIV has “incredible ability to shield itself from recognition by antibodies”. As a result, people infected with HIV “typically have only very weak neutralising activity against the virus”, further complicating efforts to develop a vaccine.
He insisted, however, that humanity "must not give up" on finding a vaccine for HIV. Scientists continue to explore various methods in the hope of one day devising a vaccine that provides effective protection against the virus.
