Promising HIV vaccine fails in a large-scale clinical trial

By Angela Betsaida B. Laguipo, BSNFeb 4 2020

The human immune deficiency virus (HIV) is an infectious disease that can lead to immunosuppression called acquired immunodeficiency syndrome (AIDS). For decades, scientists race to discover a vaccine that can help prevent the spread of the virus. The latest trial testing a new experimental vaccine in South Africa end in disappointment after deeming ineffective in preventing infection.

The National Institute of Allergy and Infectious Diseases (NIAID), which is part of the National Institutes of Health, has recommended stopping the administration of the vaccine in its HVTN 702 clinical trial of an experimental HIV vaccine. Developed by Sanofi Pasteur and GSK, the vaccine is a promising new vaccine aimed to prevent HIV infection, a disease that affected 75 million people and causing the death of 32 million people across the globe.

Vials are filled in an HIV vaccine laboratory. Fred Hutchinson Cancer Research Center

The vaccine

The vaccine study involved a new experimental vaccine regimen in a large efficacy study called the HVTN 702 or the Uhambo study. In the study, they used two experimental vaccines against HIV – ALVAC-HIV (vCP2438) and Bivalent Subtype C gp120/MF59, which were supplied by the manufacturers.

The two vaccines were created from synthetic or man-made copies of HIV pieces, and do not contain killed HIV or parts taken from the virus. In terms of safety, the vaccines are completely safe since they can’t cause HIV infection or AIDS.

The manufacturer of ALVAC vCP2438 created the vaccine using a virus called canarypox, which is designed to alert the body to produce proteins that look like those found in HIV. These proteins may trigger the immune system, which prepares the body to recognize the same proteins in HIV when infection or exposure happens in the future.

The Bivalent Subtype C gp120 vaccine came from two proteins, which are also similar to the proteins found in HIV. Both vaccines work by producing an immune response, so the next time exposure to HIV occurs, the immune system will kill the virus.

“Uhambo is a series of studies leading us to a safe and effective HIV vaccine. HVTN 702 is the latest research study in the Uhambo series. Uhambo means journey, and we are on a journey to find a safe and effective vaccine that will protect people from HIV,” the Uhambo organization said on its website.

The clinical trial

The efficacy study started in October 2016, enrolling about 5,407 sexually active, HIV-uninfected men and women who are from 18 to 35 years old at 14 locations across South Africa. The team randomly assigned half of the participants to receive a pair of the HIV vaccines, while the other half received placebo shots.

The experimental group received six injections over 18 months, and they were closely monitored throughout the study. They had been offered a local standard of care to prevent HIV, which included access to oral pre-exposure prophylaxis (PrEP).

The study was scheduled to last until July 2022, but upon the analysis of an independent monitoring board last Jan. 23, they decided that the safety and efficacy results showed that the vaccines failed to prevent infection.

The interim analysis used data from 2,694 people in the experimental group and 2,689 people from the placebo group. The analysis examined how many people were diagnosed with HIV after at least 60 percent of the participants had been in the trial for more than 18 months, which is a period ample enough to trigger an immune response.

They found that 129 HIV infections happened among the experimental group who received the vaccines, and 123 infections in the placebo recipients, showing that the vaccines were not effective in preventing infection. The independent data and safety monitoring board (DSMB) recommended to stop the trial and no further vaccinations will be given.

The participants are also recommended to stay in the study for follow-up and monitoring.

“The people of South Africa have made history by answering this important scientific question. Sadly, we wish the answer was different,” Glenda Gray, HVTN 702 Protocol Chair, said in a statement.

“We will continue to explore promising avenues for preventing HIV with other vaccines and tools, both in South Africa and around the world,” she added.