An advanced HIV vaccine study in Africa was halted after data showed the gunfire offered limited protection from the virus, researchers said Tuesday.
The vaccine manufactured by Johnson & Johnson is one in a long line that offers little protection against HIV, one of medicine’s most persistent adversaries. One vaccine candidate even increased the risk of infection.
Another study was stopped in South Africa last year after another experimental vaccine did not provide adequate protection. In 2020 around 1.5 million people worldwide were infected with HIV, and 38 million are living with the infection.
Scientists were dismayed by the recent failure.
“I should be used to it by now, but you are never used to it – you are still involved with it, heart and soul,” said Dr. Glenda Gray, the study’s lead investigator and chair of the South African Medical Research Council. Dr. Gray has been developing an HIV vaccine for over 15 years.
Completely new approaches may be required. This month, Moderna announced that it would test a vaccine based on the mRNA platform used to develop the company’s coronavirus vaccine.
The study, called Imbokodo, tested an experimental vaccine on 2,600 young women who are at high risk for HIV infection in five sub-Saharan African countries. Women and girls made up almost two-thirds of new HIV infections in the region last year.
The study was funded by Johnson & Johnson, the Bill and Melinda Gates Foundation, and the National Institutes of Health.
The vaccine was based on an adenovirus called Ad26, which was modified to carry fragments of four HIV subtypes into the body in hopes of generating an immune response that could fight off infection.
Mitchell Warren, executive director of AVAC, an advocacy group committed to AIDS prevention and treatment, said the study’s cancellation was a “reality check” amid the excitement about new vaccine technologies.
“It’s a great reminder that HIV is a pathogen that is like no other in its complexity,” he said. “We know the platform worked, but what are we putting into it? Because this virus infects exactly the same immune system that we want to strengthen with a vaccine. “
The participants in the Imbokodo study, which began in 2017, received two initial syringes and two boosters over the course of a year. The researchers tracked the number of new infections in the placebo and vaccine groups from the seventh month (one month after the third vaccination) to the 24th month.
Over a two-year period, 63 out of 1,109 people who received the placebo were infected with HIV, compared with 51 out of 1,079 people who received the vaccine – giving the vaccine a 25 percent effectiveness rate.
Previous studies, including one in Thailand, had shown that the type of antibodies this vaccine produced might be enough to offer good protection against HIV, at least for an initial period.
“But in South Africa, the higher incidence of HIV means you need something much more effective,” said Dr. Gray. “The induced immune responses just weren’t enough to stop the high attack rates we see in Africa.”
If the disappointing data showed a low rate of effectiveness, pre-study guidelines dictated that it should be discontinued. A vaccine that offered only 25 percent protection risked giving women a “false sense of security,” said Dr. Gray.
But a parallel study using a different iteration of this vaccine will continue, Johnson & Johnson said. It’s 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 subtypes of HIV in different populations and could produce different efficacy results.
Dr. Gray said the lesson from the failed attempt is to find out why it worked for the 25 percent of people who were protected rather than the others, and then to try to turn those clues into a prescription for a future vaccine, too translate.