The efficient transmission of severe acute respiratory syndrome-2 coronavirus(SARS-CoV-2)from patients to health care workers or family members has been a worrisome and prominent feature of the ongoing outbreak.On the basis of clinical practice and in-vitro studies,we postulated that post-exposure prophylaxis(PEP)using Arbidol is associated with decreased infection among individuals exposed to confirmed cases of COVID-19 infection.We conducted a retrospective cohort study on family members and health care workers who were exposed to patients confirmed to have SARS-CoV-2 infection by real-time RT-PCR and chest computed tomography(CT)from January 1 to January 16,2020.The last follow-up date was Feb.26,2020.The emergence of fever and/or respiratory symptoms after exposure to the primary case was collected.The correlations between post-exposure prophylaxis and infection in household contacts and health care workers were respectively analyzed.A total of 66 members in 27 families and 124 health care workers had evidence of close exposure to patients with confirmed COVID-19.The Cox regression based on the data of the family members and health care workers with Arbidol or not showed that Arbidol PEP was a protective factor against the development of COVID-19(HR 0.025,95％CI 0.003-0.209,P=0.0006 for family members and HR 0.056,95％CI 0.005-0.662,P=0.0221 for health care workers).Our findings suggest Arbidol could reduce the infection risk of the novel coronavirus in hospital and family settings.This treatment should be promoted for PEP use and should be the subject of further investigation.