zahra khazir - Department of nursing, Tabas school of Nursing, Birjand University of Medical Sciences, Birjand, Iran.
hamideh kouhpeikar - Vice chancellery of Treatment ، Torbat Heydariyeh University of Medical Sciences، Torbat Heydariyeh،Iran.
erfan javanmardi - MS of Biostatistics, Clinical Research Development Unit, "The Persian Gulf Martyrs" Hospital, Bushehr University of Medical Sciences, Bushehr, Iran
morad ali Zareipour - Department of Public Health, School of Health, Khoy University of Medical Sciences, Khoy, Iran
monireh gholamian - BSC in Public Health, Tabas Health Center, Birjand University of Medical Sciences, Birjand, Iran

Due to reduced levels of antibody provided by vaccines or the emergence of variants COVID-۱۹ infections have re-emerged in many countries. A considerable supplementary intervention is recommended including an additional dose of vaccination. The present study aimed to investigate the predictors of the willingness to receivethe third dose of COVID-۱۹ vaccine based on the health belief model (HBM) constructs among people referring to health centers in South Khorasan province. In this cross-sectional-analytical study, ۲۸۳ people over ۱۸ years in South Khorasan province were randomly selected by multi-stage cluster sampling method. The data were collected using a researcher-made questionnaire including demographic information and health status, knowledge about COVID-۱۹ and the third dose of the vaccine, as well as a questionnaire on based HBM constructs through self-report. Finally, the data were analyzed using Chi-square, and multivariate logistic regression. The mean age of the study participants was ۳۶.۵۷±۱۱.۵۶ with range of ۱۸-۶۶ years. The results of multivariate logistic regression analysis showed that gender (P=۰.۰۱۲), marital status(P=۰.۰۳۸), occupation (P=۰.۰۱۳), and constructs of perceived severity (P=۰.۰۰۵), and cues to action (P=۰.۰۱۸), had a significant direct effect and the construct of perceived barriers (P=۰.۰۱۰) had a significant inverse effect on the willingness to acceptance the third dose of the vaccine. Also, the predictor variables explained about ۶۷.۷% of the tendency to receive the third dose of the vaccine. The current study suggests that enhancing the perceived severity of Covid-۱۹, along with healthcareproviders recommendation to receive the vaccine and reducing perceived barriers, can effectivelyencourage individuals to receive the third dose of the Covid-۱۹ vaccine. These findings can be utilized to develop interventions aimed at promoting the uptake of the booster dose of the Covid-۱۹ vaccine.key words: COVID-۱۹, Barriers, Booster, Vaccine

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