Here's What You Need to Know About the Clostridium difficile Vaccine Efficacy Trial

Richard Haupt, MD, MPH, vice president of Medical Development at Pfizer Vaccines, sheds light on the Clostridium difficile Vaccine Efficacy Trial (CLOVER).

Interview Transcript (modified slightly for readability):

“CLOVER is the brand name, if you will, for our phase 3 clinical efficacy and safety study, and it stands for CLostridium difficile Vaccine Efficacy TRial, so it’s an acronym of that. That trial is a phase 3 trial that began in the first quarter of this year, 2017. We are enrolling subjects 50 years of age and older who are at higher risk for CDI. It’s a global study; we’re in over 20 countries around the world and we plan to enroll somewhere around 16,000 subjects. And again, this study is designed to demonstrate that our vaccine, which targets toxins A and B of C. difficile, is both safe and effective. Because it’s a clinical endpoint study, and what I mean by that is we’re assessing the ability of the vaccine to [help] prevent clinical disease—so actual cases of Clostridium difficile infection—it’s a much larger study, and that’s why we need to enroll over 16,000 subjects in the trial.

It’s what’s called an endpoint-driven trial, which means that we don’t have a necessarily a [set] time for when it stops; it’s based on accruing a certain number of events or cases in the trial, and so, how quickly those cases occur, or how slowly they occur, will define the end-timing of that clinical trial. And so, hopefully, if we’ve identified the right subjects and can enroll as quickly as possible, we’ll get the results sooner rather than later. But we have no results right now; we’re in the middle of the trial, and [we’re] enrolling and waiting for endpoints to occur.”