The only ongoing advanced (“phase 3”) trial of an HIV vaccine was terminated following disappointing results in clinical trials, marking yet another failure in the development of vaccines against the AIDS-related virus. Janssen, the vaccine division of Johnson & Johnson, announced this week it was halting a trial involving 3,900 volunteers across North America, South America and Europe and about 50 centers for treatment administration and control. .
The negative result adds to that of dozens of other experimental HIV vaccines developed in recent decades and which were then discarded. Various observers believe that the new outcome takes research back three to five years, considering that new vaccines are still under development and it will be some time before clinical trials start to verify their safety and efficacy.
The now-interrupted clinical trial was called Mosaico and was started in 2019, using a particular vaccine that contained a variety (a “mosaic”, in fact) of components against some subtypes of HIV, among the most widespread and found in most infections . However, the tests had shown that the administration did not lead to an adequate immune response, especially as regards the production of neutralizing antibodies, important in making a certain pathogen, such as a virus, harmless.
Preliminary data analysis led the independent clinical trial control group to declare the vaccine safe, but unable to prevent more HIV infections than a do-nothing substance (placebo). Consequently, the interruption of the clinical trial was recommended for ethical and practical reasons. Something similar happened in 2021 with another vaccine study, carried out in some sub-Saharan African countries.
At least at first, Mosaico seemed to be directed towards more promising results given the data collected in the previous phases of the experiment (“phase 1” and “phase 2”), which involved fewer people and whose main objective was to verify system security. Previously, at least five other experimental HIV vaccines had failed in nine clinical trials that had reached ‘phase 3’, confirming how difficult it is to develop a long overdue vaccine.
When HIV was first identified as the cause of AIDS in the early 1980s, it was thought that a vaccine against the virus could be developed relatively quickly, as had been the case for several other diseases in previous decades. . However, a few years were enough for it to become evident how difficult it was to achieve this. HIV tends to mutate quickly, eluding our body’s immune defenses and making it difficult to use a vaccine, especially if it is calibrated on some specific characteristics of the virus. In addition, HIV has many subtypes and creates ‘reservoirs’ in the body, which can remain dormant for years without AIDS developing.
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It is estimated that HIV infects around 1.5 million people each year and causes 650,000 deaths. According to the most shared estimates, over 75 million people have died since the beginning of the AIDS epidemic, especially in less economically advanced countries, where it is more difficult to obtain adequate treatment to keep the disease under control and there is not always great awareness of the prevention. Some types of drugs such as antiviral drugs prevent the virus from continuing to multiply in people who have it. Some treatments consist of periodically taking pills or undergoing injections and transfusions. Since there is no cure, the treatment must be carried out for life and in some subjects it can lead to adverse effects, both in the short and in the long term.
In addition to reducing the risk of infection, an effective HIV vaccine would be an important benefit for countries where treatments are not accessible because they are too expensive, or where they cannot be provided adequately following patients. Interest in a vaccine therefore remains high, even if the new negative result will have repercussions on the development of new solutions.
– Read also: We need to talk differently about HIV
Various experts have begun to ask themselves whether a change of approach is necessary, starting precisely from rethinking techniques and methods for inducing an adequate immune response. A new area that could offer some promising results comes from messenger RNA vaccines, such as those used against the coronavirus in these pandemic years. Some trials are already underway, but we will still have to wait for the start of clinical trials, which in turn will take some time before being able to verify the effectiveness of the new approach.
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