Estimation of outpatient SARS-CoV-2 reinfection and recurrence rates and associated factors among COVID-19 hospitalized patients over one-year old: a multicenter retrospective cohort study

IntroductionReinfection with SARS-Cov-2 after recovery can occur that most of them don't require hospitalization. The aim of this study is estimation of out-patient COVID-19 reinfection and recurrence rates and its associated factors among Iranian patients with history of confirmed SARS-Cov-2 infection and hospitalization.MethodsThis study is a retrospective cohort conducted from May 2021 to May 2022 in Iran. The national Medical Care Monitoring Center (MCMC) database, obtained from the Ministry of Health and Medical Education, includes all information about confirmed COVID-19 patients who are hospitalized and diagnosed during the pandemic. Using probability proportional to size sampling from 31 provinces, 1,532 patients over one years of age with a history of hospitalization in the MCMC data are randomly selected. After that, interviews by phone are performed with all of the selected patients using a researcher-made questionnaire about the occurrence of overall reinfection without considering the time of infection occurrence, reinfection occurring at least 90 days after the discharge and recurrence (occurring within 90 days after discharge). Univariate and multivariable Cox regression analyses are performed to assess the factors associated with each index. All of the analyses are performed using Stata software version 16.ResultsIn general, 1,532 phone calls are made, out of which 1,095 individuals are willing to participate in the study (response rate similar or equal to 71%). After assessing the 1,095 patients with a positive history of COVID-19, the rates of non-hospitalized overall SARS-Cov-2 reinfection, reinfection and recurrence are 122.64, 114.09, and 8.55 per 1,000 person-years, respectively. The age range of 19-64 years (aHR:3.93, 95%CI : 1.24-12.41) and COVID-19-related healthcare worker (aHR: 3.67, 95%CI: 1.77-7.61) are identified as risk factors for reinfection, while having comorbidity, being fully vaccinated, and having a partial pressure of oxygen (PaO2) >= 93 mmHg during the initial infection are identified as factors that reduce the risk of non-hospitalized reinfection.ConclusionReinfection due to COVID-19 is possible because of the weakened immune system for various reasons and the mutation of the virus. Vaccination, timely boosters, and adherence to preventive measures can help mitigate this risk.