Background: After a successful experiment in rats with anaerobic vaccine in combating peritonitis in the model of ceacal ligation and puncture to prevent sudden death, it was decided to undergo a clinical study. Material and methods: 445 patients who underwent major and semimajor operations were vaccinated each with 0.25 mL of covexin 10 before operation. Results: Infection of the wounds occurred in 24 of 445 patients (5.4 %). Infection occurred in 7 of 202 who underwent breast operations, mostly for breast cancer including axillary dissection (3.5 %). Infection occurred in 2 of 50 who underwent major operation for colorectal cancer (4%). 3 of 43 patients who underwent major operation for urinary bladder cancer developed wound infection (7.0%). Other operations for other sites were associated with a low incidence of wound infection compared to historical control. Although, it was a large series of major operations, not a single case developed multiple organ failure syndrome. Discussion: Because of success of anaerobic vaccination in combating post-operative wound infection, we recommend that researchers in this field to start similar clinical trials. Because multiple organ dysfunction syndrome was not encountered in this series, a possible etiology of the syndrome may be due to toxins released from anaerobic sepsis in small bowl. Conclusion: Vaccination with anaerobic vaccine was successful in reducing post-operative wound infection to about half of historical control. Key words: wound infection, anaerobic vaccine, and anaerobic infection. No. S19/P4, page 90, Microbiology Society Annual Conference 2016, Liverpool, UK.