Sanofi Pasteur, the vaccines division of the sanofi-aventis Group, has expanded its phase-II clinical study of a vaccine against Clostridium difficile infection (CDI) into the United States. The trial started in the United Kingdom earlier this year.

The incidence of CDI has increased significantly in recent years in both North America and Europe. CDI-related treatments in these two regions of the world are estimated to be costing more than US$ 7 billion a year. The recent emergence and spread of a hyper-virulent strain of C.difficile further highlights the importance of tackling CDI.

“While the target indication for the vaccine is prevention, this trial - in recently infected patients - aims to provide early proof-of-concept of a vaccine approach to preventing recurring infection,” said Michel DeWilde, senior vice president, Research and Development, Sanofi Pasteur. “Recurring infection occurs in at least 20 percent of patients experiencing a first CDI episode and even higher frequency in those who have had multiple episodes,” he explained.

CDI is among the most common causes of nosocomial (hospital-acquired) infection in North America and Europe. Current treatment of C.difficile infection involves the use of one of the two antibiotics recommended for CDI management. The trial is investigating the safety and efficacy of Sanofi Pasteur’s CDI candidate vaccine in the US population.

“Non-antibiotic approaches for managing CDI are badly needed since antibiotics alter the gut micro-flora and permit the infection in the first place,” said Dr DeWilde. “There is also considerable concern about the emergence of antibiotic-resistance in various bacterial species, including C.difficile. Vaccination has the potential to be a very effective strategy to combat the gastrointestinal symptoms caused by C.difficile in conjunction with better antibiotic stewardship and infection control practices,” he added.

Sanofi Pasteur’s candidate vaccine uses a toxoid-based approach, which has been used extensively in licensed vaccines against tetanus, diphtheria and pertussis (whooping cough). This candidate vaccine has successfully completed phase I clinical trials in more than 200 participants to evaluate its safety and immunogenicity.

C.difficile is an anaerobic spore-forming bacterium, present asymptomatically in approximately 60 per cent of infants but only approximately three percent of healthy adults.