 This study assessed the safety and immunogenicity of costridium difficile vaccine in healthy Japanese adults aged 40 to 75 years old, finding high seroconversion rates for both toxin A and B, with lower response to toxin B evaluated using TNA. The proportion of participants with solicited local reactions, systemic reactions, and unsolicited reactions were 67.6%, 19.1% and 20.6%, respectively, with most adverse reactions being mild to moderate in intensity and resolving by three to six days post-vaccination. No withdrawals due to adverse events or serious adverse events occurred. This article was authored by Osomomotsuoka, Doval M Patel, Shinsasaki, and others.