C. diff is a bacterium that causes severe diarrhea and inflammation of the colon. It is especially prevalent in hospitals and long-term care facilities and is one of the most common health care–associated infections in the United States. According to the National Foundation for Infectious Diseases, nearly 500,000 Americans develop C. diff infections each year, leading to approximately 30,000 deaths.
“It’s always better to prevent C. diff than to treat it … It can be life threatening.” — Kristen Pierce, M.D.
C. diff spreads through spores, which become active after being swallowed and reaching the intestines. Most healthy people do not become infected when exposed to C. diff, because a healthy gut microbiome helps protect against infection by supporting the body’s natural defenses. Antibiotics can disrupt those protective bacteria, increasing the risk of illness. Alcohol-based hand sanitizers do not kill C. diff spores, but handwashing with soap and water helps prevent infection.
While C. diff can affect anyone, older adults are at greatest risk, particularly those who have recently used antibiotics or experienced extended hospital stays. Additional risk factors include a weakened immune system and prior C. diff infections.
Although treatments for C. diff infections are available, recurrence is common. Many people who develop C. diff experience repeated infections, making prevention a critical public health goal. That’s why a vaccine to prevent it is crucial, says infectious disease physician Kristen Pierce, M.D., the study’s principal investigator in Vermont.
“It’s always better to prevent C. diff than to treat it, and so it’s really important to find a good vaccine,” says Dr. Pierce, professor of medicine and co-director of the Vaccine Testing Center at the Robert Larner, M.D. College of Medicine at the University of Vermont. “It’s not just diarrhea; it can be life threatening.”
Beyond physical symptoms, C. diff can also have profound social and emotional impacts. Severe diarrhea can be painful and isolating; concerns about transmitting the infection can disrupt patients’ daily activities and relationships.
Previous studies have shown that the C. diff investigational vaccine, developed by Pfizer, is safe, tolerable, and effective. The current Phase 3 study will further evaluate the vaccine’s safety and whether it can prevent C. diff infection or reduce illness severity in adults age 65 and older.
Participants will be randomly assigned to receive either two doses of the vaccine or a placebo. Participation may last up to three and a half years and will include in-person visits, telephone check-ins with research staff, and reporting of loose stool episodes. Participants may receive up to $1,320 in compensation.
To learn more about the study and determine eligibility, visit the Department of Microbiology and Molecular Genetics Volunteer webpage, call (802) 656-0013, or email UVMVTC@uvm.edu.