A major clinical trial of two new HIV vaccine combinations in Africa has been halted after an interim analysis showed they had little or no chance of preventing infection.
The trial, known as PrEPVacc, involved more than 3,000 volunteers from Uganda, Tanzania, Mozambique, and South Africa who were at high risk of acquiring HIV. They received four injections of either one of the two vaccine regimens or a placebo over a year.
The vaccines were designed to stimulate the immune system’s killer T cells, which can destroy virus-infected cells, and target regions of the HIV that are common across different strains. The hope was that they would offer better protection than the only vaccine that has shown some efficacy so far, the RV144 vaccine tested in Thailand in 2009, which reduced the risk of infection by about 30%.
However, an independent data monitoring committee found that the PrEPVacc vaccines were unlikely to show any significant benefit over the placebo, based on the number of infections that occurred in the trial. The committee recommended stopping the vaccinations but continuing to follow up with the participants and evaluate the use of a daily pill to prevent HIV, known as pre-exposure prophylaxis (PrEP).
The researchers expressed their disappointment, but also their gratitude to the volunteers and the communities that took part in the trial. They said the results would provide valuable information for future HIV vaccine development.
Dr. Eugene Ruzagira, the trial director from the Uganda Virus Research Institute, said: “Vaccinations to PrEPVacc trial participants have been stopped because an analysis of the data collected so far by our independent data-monitoring committee has led them to conclude that there is little or no chance of demonstrating that the vaccines we are testing are reducing the risk of acquiring HIV.”
Prof Glenda Gray, the chief investigator of PrEPVacc at the South African Medical Research Council, said: “It is a goal that must have even greater urgency now that no HIV vaccines are being trialed for efficacy anywhere in the world. We have come so far in our HIV-prevention journey, but we must look to a new generation of vaccine approaches and technology to take us forward again.”
The PrEPVacc trial was part of a larger initiative called the European and Developing Countries Clinical Trials Partnership (EDCTP), which aims to accelerate the development of new or improved drugs, vaccines, and diagnostics for diseases that affect low- and middle-income countries. The trial was funded by a €15 million grant from the European Union and supported by several research institutions, pharmaceutical companies, and health organizations.
According to the World Health Organization, 37.7 million people were living with HIV globally in 2020, and 1.5 million new infections. Sub-Saharan Africa remains the most affected region, accounting for 66% of all people living with HIV and 69% of new infections.
Despite the setback, the researchers and their partners remain committed to finding an effective and safe HIV vaccine, which they believe is essential to end the AIDS epidemic. They also stressed the importance of continuing to use the existing prevention methods, such as condoms, PrEP, voluntary medical male circumcision, and antiretroviral therapy.
Dr Ruzagira, speaking at an AIDS conference in Zimbabwe, said: “The scientific hurdles are high, but I have equally high hopes that an HIV vaccine will be developed one day.”
Source: International Business Times
