According to a report published in the March 25 issue of the New England Journal of Medicine, a canarypox-protein HIV vaccine regimen (ALVAC-HIV) plus bivalent subtype C gp120-MF59 adjuvant does not prevent HIV-1 infection among adults in South Africa.

In a phase 2b-3 trial in South Africa, Glenda E. Gray, M.B., B.Ch., from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues randomly allocated 5,404 adults without HIV-1 infection to receive canarypox-protein HIV vaccine or placebo (2,704 and 2,700 participants, respectively). Injections of ALVAC-HIV were given at months 0 and 1, followed by injections of ALVAC-HIV plus bivalent subtype C gp120-MF59 adjuvant boosters at months 3, 6, 12, and 18.

Prespecified requirements for nonefficacy were reached at an interim review in January 2020, according to the researchers, and further vaccinations were subsequently halted. The vaccine and placebo groups both had a similar rate of adverse effects. During the 24-month follow-up, HIV-1 infection was observed in 138 and 133 participants in the vaccine and placebo classes, respectively (hazard ratio, 1.02; 95 percent confidence interval, 0.81 to 1.30; P = 0.84).

The authors write, “Despite promising immunogenicity, this canarypox-protein HIV vaccine regimen was not successful in preventing HIV-1 infection in our trial population in South Africa.” “The high HIV-1 incidence we saw in our study exemplifies the epidemic’s unrelenting existence, especially among young women.”

Novartis Vaccines and Diagnostics, which is now part of GlaxoSmithKline Biologicals, sponsored the research and also contributed financially to the trial participants’ preexposure prophylaxis.