HCV vaccine regimen fails to prevent chronic infections
WASHINGTON — An investigational vaccine regimen failed to prevent chronic hepatitis C virus infection in a cohort of at-risk adults, according to results of a clinical trial presented at IDWeek.
Recently, study findings published in The Lancet suggested the WHO goal to eliminate HCV globally by 2030 will be “narrowly missed.” A vaccine, researchers said, will be crucial to elimination efforts.
Andrea L. Cox, MD, PhD, a professor of medicine at Johns Hopkins University, and colleagues conducted the first prophylactic HCV vaccine efficacy trial — a randomized, multicenter, double-blind, placebo-controlled study called Vaccine is Prevention. The vaccine regimen is based on viral vectors, consisting of a recombinant chimpanzee adenovirus 3 vector vaccine prime followed by a recombinant modified vaccinia Ankara virus boost. In the study, 455 participants aged 18 to 45 years who injected drugs received either the vaccine regimen or placebo at days 0 and 56.
The study took place at three sites in the United States — the University of California, San Francisco, Johns Hopkins and the University of New Mexico, Cox said.
According to the researchers, the overall incidence of HCV infection at 6 months was 13 infections per 100 person-years. This is substantially lower than the incidence in the background populations of the study sites, Cox said, probably because of “aggressive counseling and referral to drug treatment and needle exchange programs” during the trial.
Cox and colleagues found no difference in the development of chronic infection between the vaccine and placebo arms, with 14 cases in each. The regimen’s efficacy in preventing chronic infection was –0.53 (95% CI, –2.5 to 0.34).
However, the vaccine regimen blunted the peak HCV RNA level in recipients 1 month after vaccination compared with placebo — a statistically significant finding, Cox noted. In terms of immunogenicity, the vaccine regimen induced an immune response in 78% of recipients, which is a less robust response that what was observed in an earlier study of healthy volunteers, she said.
According to the researchers, there were no safety signals in the study, and the regimen was well-tolerated, with no serious vaccine-related adverse events.
“There remains a significant need for vaccine to interrupt transmission, and it will be critical for achieving WHO elimination goals,” Cox said. “Testing vaccines in [people who inject drugs] is possible, but additional strategies will need to be considered — ideally, with information gained from this vaccine, informing future vaccine design.” – by John Schoen
Cox AL, et al. Abstract LB10. Presented at: IDWeek; Oct. 2-6, 2019; Washington.
Disclosure: Cox reports no relevant financial disclosures.