December 1 – World AIDS Day. Almost half a century ago, the human immunodeficiency virus HIV/AIDS was discovered, but there is still no vaccine against it. Why not?

Just a few months after the world learned about the new coronavirus SARS-CoV-2, many promising candidate vaccines appeared. It is hoped that next year, and maybe this year too, the world will receive its first coronavirus vaccine. Meanwhile, there is still no vaccine against the human immunodeficiency virus (HIV/AIDS), which was detected about 40 years ago. Why not? The answer is simple: the human immunodeficiency virus is a chameleon among all other viruses, it is constantly changing, mutating, which negates all attempts by scientists to create an HIV vaccine.

What does the human immunodeficiency virus look like?

HIV/AIDS vaccine: why hasn't it been invented so far?

Human immunodeficiency virus has a complex three-dimensional surface structure, with half of it covered with a sugar shell, glycolized, as scientists say. It is glycolized surfaces that block the vaccine action.
Had HIV behaved like other viruses, this would have made it much easier for the vaccine developer. But the human immunodeficiency virus is constantly and very quickly changing its envelope. To defeat this virus, the immune system has to recognize it, but its rapid mutation means that the immunity does not see it as a danger.
The human immunodeficiency virus belongs to the retrovirus group. They have the ability to store their DNA gene in a human cell. Scientists have been trying for years to understand how retroviruses multiply in order to develop a strategy to combat them. But so far, to no avail.

Which vaccines are being developed against HIV

HIV/AIDS vaccine: why hasn't it been invented so far?

The development of a vaccine called HVTN 7026, which began in 2016 in South Africa, was very promising. 5407 HIV-negative people aged 18 to 35 years participated in the vaccine’s trials. The vaccine used the Prime Boost method, in which two vaccines were combined. With the first (Prime) vaccine, a person received a different serum than with the second (Boost) vaccine. Thus, the chances for the immune system should have doubled, but this did not happen.
The basis for HVTN 7026 was the RV 144 vaccine. It is the only serum that showed a rather modest 31 percent efficacy level during the trials in Thailand. It is true that this vaccine can only protect a person from the virus for a few months. In February 2020, its trials were interrupted because there was no obvious success.
The next attempt to develop an HIV/AIDS vaccine was Project MOSAICO. It was also based on the method of combining the two vaccines. MOSAICO vaccine was tested on monkeys and the results were promising. With this vaccine, the risk of HIV/AIDS infection in 90 percent of cases could have been reduced. Since late 2019, the United States has been running clinical trials with this vaccine. 3,800 people are participating in it.
A third vaccine is being developed under the name IMBOKODO. Its trials involve 2,600 people from various African countries. The effectiveness of the vaccine is still 67 percent. Its trials will end in February 2022.
So far, scientists are confident that any vaccine developed will not provide 100 percent protection against HIV. But a vaccine that provides 60 to 70 percent protection would be considered a success. Until then, the only option left is to treat HIV/AIDS with antiretroviral drugs.

Why pre-exposure prophylaxis is important

Since a vaccine against the human immunodeficiency virus has not yet been invented, high hopes are placed on HIV/AIDS drug prevention, the so-called pre-exposure prophylaxis, which is a preventive measure to prevent HIV transmission carried out by an HIV-negative partner. Currently, scientists are looking for an alternative to the pills that need to be taken every day. This includes injections or implants, which contribute to the accumulation of the necessary preparation against the virus in the body.