Researchers announced on Tuesday that an advanced study for a vaccine against HIV in Africa was closed after data showed that the doses offered limited protection against the virus. The vaccine, produced by Johnson & Johnson, is one of many that offer little defense against the HIV, one of medicine’s thorniest opponents. One of the vaccine candidates even increased the risk of infection.
Another study was stopped last year in South Africa after a different experimental vaccine failed to provide sufficient protection. About 1.5 million people were infected with HIV around the world in 2020, and 38 million are living with the infection.
Scientists were dismayed by this latest failure. “I should be used to it by now, but you never are – you still put your heart and soul into it,” said Dr. Glenda Gray, the study’s principal investigator and head of the South African Medical Research Council.
Gray has been working for more than 15 years on developing an HIV vaccine. Totally new approaches may be needed. Moderna announced earlier in August that it would test a vaccine based on the mRNA platform used to create its coronavirus vaccine.
The study, called Imbokodo, tested an experimental vaccine on 2,600 young women considered at high risk for HIV infection in five countries in sub-Saharan Africa. Women and girls accounted for nearly two-thirds of new infections in the region in the last year.
The study was funded by Johnson & Johnson, the Bill and Melinda Gates Foundation and the National Institutes of Health. The vaccine used an adenovirus called Ad26, modified to transport fragments of four HIV subtypes into the body in hopes of eliciting an immune response that could protect against infection.
Mitchel Warren, executive director of AVAC, a group that advocates and lobbies for AIDS prevention and treatment, said the study’s cancellation was “a wash of reality” amid enthusiasm for new vaccine technologies.
“It’s a great reminder that HIV is a pathogen unlike any other in its complexity,” he said. “We know the platform worked, but what did we put on it?” Because this virus is infecting the exact same immune system that we’re trying to boost with a vaccine.”
Participants in the Imbokodo study, which began in 2017, received two initial doses and two boosters over the course of a year. The researchers tracked the numbers of new infections in the placebo groups and the vaccinated group from the seventh month (one month after the third dose) to the twenty-fourth month.
Over two years, 63 of the 1109 participants who received the placebo became infected with HIV, compared with 51 of the 1079 participants who received the vaccine – giving the vaccine an efficacy rate of 25%. Previous studies, including one carried out in Thailand, have indicated that the types of antibodies this vaccine produced may be sufficient to provide good protection against HIV at least initially.
“But in South Africa, the high HIV incidence rates mean you need something much more potent,” Gray said. “The types of immune responses induced simply weren’t enough to stop the high infection rates we see in Africa”
When disappointing data showed a low efficacy rate, guidelines established before the study called for the study to be terminated. A vaccine that offered only 25% protection risked giving women a “false sense of security,” Gray said.
But a parallel study using a different interaction from this vaccine will continue, Johnson & Johnson said. It is being tested on men who have sex with men and transgender people in eight countries including Poland, Brazil and the United States. This study, called Mosaico, is testing the vaccine against different HIV subtypes in different populations, and could produce different efficacy results.
Gray said the lesson of the failed study is to find out why it worked for 25% of people who were protected and not others, and then try to translate those clues into a prescription for a future vaccine. / TRANSLATION LÍVIA BUELONI GONÇALVES