Objective To investigate the vaccination rate of Coronavirus Disease 2019 (COVID-19) vaccine in patients undergoing cardiac mechanical valve replacement and to evaluate its effect on international normalized ratio (INR) value. MethodsWe investigated 132 patients who had received cardiac mechanical valve replacement and followed up in the Department of Cardiovascular Surgery, West China Hospital of Sichuan University from May to October 2021. There were 51 males and 81 females aged 26-72 (53.01±9.51) years. ResultsThe vaccination coverage rate was 53.8%. Among the 61 unvaccinated patients, concerns about heart side-effects were the main reason. The average INR of the first review after vaccination was higher than that of the last review before vaccination, with a difference of 0.40±0.72 (P<0.001). ConclusionThe vaccination rate of patients after cardiac mechanical valve replacement is low. At the same time, COVID-19 vaccine may increase INR value, and it is suggested that patients should increase the frequency of review and adjust warfarin dosage after vaccination.