C. difficile Vaccine Candidate Reported Safe for Seniors

A recent phase 2 clinical study reported the Clostridium difficile (C. difficile) vaccine candidate PF-06425090, was reported safe, well-tolerated and immunogenic in healthy seniors. 

This is good news since there is not a C. difficile vaccine available today. 

The Pfizer vaccine tested in this study was designed to induce high levels of C. difficile toxin-neutralizing antibodies. 

This study found the PF-06425090 vaccine to be immunogenic when administered to healthy adults aged 65 to 85 years at either 100- or 200-μg dose levels, delivered at 0, 1, and 6 months or 1, 8, and 30 days. 

The month regimen, particularly at the 200-μg dose level, induced more robust and persistent immune responses when compared with the ‘day’ regimen. 

Immune responses for both dose levels in the month regimen were much higher post-dose 3, particularly for toxin B, and remained elevated above baseline through 12 months post-dose 3 at both dose levels. 

Baseline seropositivity was associated with greater immune responses, particularly for toxin B. 

This study was conducted from July 2015 through March 2017, in 855 healthy adults aged 65-85 years from 15 centers. The participants were randomized 3:3:1 to receive the vaccine (100 or 200 μg) or placebo at 0, 1, and 6 months (month regimen) or 1, 8, and 30 days (day regimen). 

Several ongoing and recently completed studies will further evaluate immune persistence, response to a booster, and inform the use of this vaccine. 

Overall, this study demonstrated encouraging tolerability and immunogenicity, supporting the continued development of the PF-06425090 C. difficile vaccine for seniors. The 200-μg dose level was selected for development in an ongoing phase 3 studies.

C. difficile caused almost half a million infections among patients in the United States in a single year, according to a study released by the Centers for Disease Control and Prevention (CDC). 

Approximately 29,000 patients died within 30 days of the initial diagnosis of C. difficile.  Of those, about 15,000 deaths were estimated to be directly attributable to C. difficile infections, making C. difficile a very important cause of infectious disease death in the United States.   

C. difficile causes an inflammation of the colon and deadly diarrhea.

More than 80 percent of the deaths associated with C. difficile occurred among Americans aged 65 years or older, says the CDC.

Approximately two-thirds of the C. difficile infections were found to be associated with an inpatient stay in a health care facility, but only 24 percent of the total cases occurred among patients while they were hospitalized.  

Almost as many cases occurred in nursing homes as in hospitals, and the remainder of the healthcare-associated cases occurred among patients who were recently discharged from a health care facility.  

More than 80 percent of the deaths associated with C. difficile occurred among Americans aged 65 years or older, says the CDC.