Infectious Disease

Results of “really disappointing” HIV vaccine study published

March 24, 2021

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Gray does not report any relevant financial information. In the study you will find all relevant financial information from all other authors.

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The researchers released data from a late-stage clinical trial of a once promising HIV vaccine candidate more than a year after the trial was stopped prematurely because the vaccine did not prevent infection.

The researchers found nearly identical infection rates in patients in the HVTN 702 study, regardless of whether they received the HIV vaccination schedule or the placebo.

HIV Vaccine Failed Infographic

Source: Gray GE et al. N Engl J Med. 2021; doi: 10.1056 / NEJMoa2031499.

“The high incidence of HIV-1 that we observed in our study shows the relentless aspect of the epidemic, especially among young women,” said the chairman of the HVTN 702 protocol Glenda E. Gray, MBBCH, FCPAED, The President and CEO of the South African Medical Research Council and colleagues wrote in the New England Journal of Medicine. “More than ever, an effective vaccine is needed to prevent the acquisition of HIV-1 in different populations.”

Gray and colleagues enrolled 5,404 HIV-negative adults in South Africa to test a vaccine based on a regimen found to be around 31% effective during the RV144 vaccine study in Thailand more than a decade ago. Researchers randomly assigned participants in the new study to either receive the vaccination schedule – injections of a canarypox vector-based vaccine called ALVAC-HIV at months 0 and 1, followed by four booster injections of ALVAC-HIV with the divalent subtype C gp120-. MF59 adjuvant during months 3, 6, 12, and 18 – or a placebo.

A total of 2,704 adults received the vaccine and the remaining 2,700 received a placebo. The primary outcome of the study was HIV-1 infection between randomization and 24 months.

According to the results, there were 138 infections in the vaccine arm and 133 in the placebo arm (HR = 1.02; 95% CI, 0.81-1.3).

The researchers wrote that one of the study’s main limitations was the inability to compare the regimens used in the RV144 study, which produced only short-lived CD4 and T-cell responses, and the HVTN 702 study.

“Additional studies of the immunological properties and virus sequences are underway to improve our understanding of the findings and implications for this research area,” wrote Gray and colleagues. “Given the differences between the vaccines and the immune responses they generate, as well as the differences in the level of virus exposure and the extent of matching, it will be difficult to determine which factor or combination of factors is responsible for the different efficacy outcomes in the two studies between the vaccines and the exposing viruses, as well as host genetics and other host factors. “

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Paul A. Volberding, MD

Paul A. Volberding

The world needs an effective HIV vaccine. This is the case more than three decades after HIV was discovered and the promise of vaccine delivery within two years at the first international AIDS conference in 1985. Despite a tremendous (and expensive) effort, only one candidate vaccine trial, RV144, conducted in Thailand and published in 2009, even reported modest efficacy.

The current study in South Africa was based in part on this earlier work, but with additional elements aimed at increasing the benefit in preventing infection in a region with a high prevalence of HIV subtype C and a much higher background incidence of HIV. More than 5,400 young, uninfected adults took part in the study (ALVAC-HIV and divalent subtype C gp 120-MF59). Half received the active vaccine and the rest received a placebo. They were then followed up for new cases of HIV infection. Despite preliminary evidence in previous small studies on the immunogenicity of this approach, the current study was definitely negative. The number of infections in each group was almost identical and the viral load after infection was not decreased in the recipients of the active vaccine. This is truly disappointing and underscores the urgent need to further facilitate access to ART and PrEP of all types and other prevention strategies as we continue to search for an effective vaccine. Given the remarkable success in developing SARS-CoV-2 vaccines and newer technologies used in these efforts, we can remain confident. However, this is not an encouraging development.

Paul A. Volberding, MD

Editor-in-Chief, Infectious Disease News

Professor emeritus for medicine

University of California, San Francisco

Disclosure: Volberding reports on advising Gilead Sciences and chairing a Merck supervisory board on data security.

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