摘要Objective:To determine the frequency and severity of the breakthrough infections and the associated factors in Malaysia.Methods:This cross-sectional study was conducted among the adult general population in Malaysia who completed at least one dose of vaccination.The validated online questionnaires were used for data collection between December 2022 to February 2023.The participants were recruited by a convenient sampling method.The data were analysed by descriptive statistics,and logistic regression by using SPSS(Version 27).Qualitative data from open-ended questions were analysed as thematic analysis by using RQDA software.Results:A total of 524 participants'data were analyzed and 77.5%of them completed three doses of COVID-19 vaccination.Breakthrough infections after vaccination were reported in 57.3%of the participants.Age group of 18 and 30 years(a OR 2.32,95%CI 1.01-5.32)and other ethnicities(aOR 2.00,95%CI 1.02-3.93)significantly associated with the occurrence of breakthrough infections.A total of 35.5%of the participants were not willing to take another booster dose in the future because of their attitudes towards fear of long-term side effects,lack of trust to the vaccine,less susceptibility to severe infection,belief in natural immunity,and myths.Conclusions:Future public health policies and interventions should be focused on disseminating the information about safety of booster doses of vaccine,management and re-assurance of side effects,and targeted vaccination to the working(younger age group)and ethnic minorities.