Stories

CHR Tests Pfizer Vaccine to Protect Older Adults

By Jill Pope, Communications Lead

In January 2026, CHR saw its first participant for the BEETHOVEN Study, a new clinical trial sponsored by Pfizer. The study is led by Distinguished Investigator Richard Mularski, MD, and will test a vaccine to protect against Clostridioides difficile (C. diff) infection among people age 65 and older.

C. diff is a leading cause of infections in hospitals, nursing homes, and long-term care facilities. People who become infected can suffer from severe diarrhea, fever, and nausea, and infections can be life-threatening. People age 65 and older and those who have recently taken antibiotics are at higher risk.

“Infections from C. diff are surprisingly common—500,000 are estimated yearly in the U.S. to become infected and this disease carries significant burden,” Dr. Mularski said. “Because standard alcohol-based hand cleaners don’t kill the bacteria and spread is catastrophic in care facilities, patients are placed in closed-off rooms and staff wear special gowns and gloves to care for them, causing isolation both from providers and their family. The public health concerns make it hard for patients to leave a hospital to go to a nursing home due to restrictions placed on infected patients.”

C. diff can also pose a very serious health risk, Dr. Mularski said. “Many patients have recurrence of infections, significant symptoms including weight loss and pain, and up to one in eleven over the age of 65 die within a month of infection. Recently, I’ve seen two patients die of C diff. I kept thinking, what if we already had an effective vaccine?”

Pfizer hopes to change that with the BEETHOVEN Study, a large, Phase 3 clinical trial that aims to enroll 32,000 adults age 65 and older in the U.S., Argentina, the U.K., and Japan. The goal is to learn how effective the C. diff vaccine is in decreasing infections and to evaluate the safety of the vaccine.

In the new clinical trial, participants will be randomly assigned (by chance) to receive either the C. diff vaccine or a placebo. They will attend at least five study visits; at two visits, they will receive either a vaccine dose or placebo (saline). They will use an e-diary to check in and report any diarrhea symptoms weekly for up to three and a half years, and they may be asked to collect and return stool samples.

CHR began recruiting participants for the trial in December 2025. “Our site hopes to enroll 900 patients in 18 months, which is ambitious, but we're off to a great start,” said Cassie Boisvert, the study’s project manager. “We've been pleasantly surprised by the amount of interest.” The study team has already conducted more than 50 participant visits, making CHR the trial’s fourth leading recruitment site.

Some of the early interest has come from Kaiser Permanente Northwest (KPNW) health plan members who participated in a previous C. diff vaccine trial called CLOVER, also sponsored by Pfizer. The vaccine tested in that trial showed promise but didn’t reduce infection.

Even so, CHR’s success in enrolling participants paid off. “Because CHR was the highest enrolling site in the CLOVER trial, Pfizer approached us about a year ahead of the [new] trial start,” Boisvert said. “There's a lot of interest from past participants. There were about 450—and half of them that received placebo in the past are eligible to participate in BEETHOVEN.”

KPNW members who may be eligible to participate are identified using medical records and will receive an email and a letter about the study. Says Boisvert, “When members get our e-mail or our letter, they get a link to a survey to see if they're eligible. I think patients appreciate the option of the brief survey to express interest versus having to compose an e-mail or give us a call.” She adds, “We haven't had to do any cold calling yet, which has been pretty outstanding. We're trying to just reach out to a large number of people and capture interested patients.”

CHR is actively recruiting for the BEETHOVEN study. You may be eligible if you are a KPNW member age 65 or older. Find out more here.