Highly effective antiviral treatments for HIV are available, but those living with the virus must take them for the rest of their life, and the long-term health effects of infection remain challenging.
In addition, access to prevention and treatment services is limited in some parts of the world.
The World Health Organization (WHO) estimates that, as a result, there were 1.7 million new infections with HIV in 2019, and 690,000 people died from HIV-related causes.
Despite decades of work, scientists have failed to develop an effective vaccine against the virus.
The reason for this is that most of the surface of the virus is densely coated with sugar molecules that do not trigger an immune response, and the parts that are exposed are highly variable.
As with SARS-CoV-2, which is the virus that causes COVID-19, HIV uses spike proteins on its outer surface to gain entry to its host cells.