Cases of reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported worldwide. We investigated reinfection cases in a set of more than 30,000 samples, and the SARS-CoV-2 genomes from selected samples from four patients with at least two positive diagnoses with an interval ≥ 45 days between tests were sequenced and analyzed. Comparative genomic and phylogenetic analysis confirmed three reinfection cases and suggested that the fourth one was caused by a virus of the same lineage. Viral sequencing is crucial for understanding the natural course of reinfections and for planning public health strategies for management of COVID-19.