Reinfection following COVID-19 is possi- ble, but rare, according to a study published in Clinical Infectious Diseases. Investigators assessed the rate of reinfection, associated factors, and mortality during follow up in 9,119 patients with SARS-CoV-2. Patients received serial tests in one of 62 healthcare facilities between December 1, 2019 and November 13, 2020. Reinfection was defi ned as two positive tests during an interval of more than 90 days follow- ing resolution of fi rst infection determined by two or more consecutive negative tests. Rein- fection occurred in 0.7% of patients. e mean period between two positive tests was 116 days. Asthma (odds ratio [OR], 1.9) and nicotine dependence/tobacco use (OR, 2.7) were asso- ciated with reinfection. Compared with the primary infection, there was a signifi cantly lower rate of pneumonia, heart failure, and acute kid- ney injury during reinfection, although two deaths were associated with reinfection. “ is is one of the largest studies of its kind in the US, and the important message here is that COVID-19 reinfection after an initial case is possible, and the duration of immunity that an initial infection provides is not completely clear,” the lead author said in a statement.