Information on the long-term immunity conferred by infection with SARS-CoV-2 is scant. Patients tested for COVID-19 infection via PCR at one health system in Ohio and Florida from March 12, 2020 to February 24, 2021 were included. During the study period, 612,611 tests were collected from 386,336 individuals (average age 51.4 ± 22.4 years, 54.5% female), with a 9.9% overall positivity rate. In this retrospective cohort, patients who initially tested positive for COVID-19 were less likely to be subsequently tested or test positive than those who initially tested negative during the same time period. Most reinfected patients were asymptomatic. Protection of prior infection against symptomatic disease was 85%, and even including asymptomatic cases, protection offered against reinfection was 82%. Few patients were hospitalized following reinfection, and none with COVID-related symptoms required intensive care, suggesting a high level of protection against severe disease. Six months after infection, protection against symptomatic disease exceeded 90%. This measure of reinfection may have overestimated the actual reinfection rate, because some patients may continue to shed virus for many months, it can be difficult to differentiate between reinfection and persistent shedding. In light of these findings, as well as other evidence of the persistence of immunity after infection, the CDC may wish to revisit its recommendation to immediately vaccinate previously infected individuals. Based on this study, patients with known history of infection could consider delaying vaccination for at least 8 months, freeing up vaccine to protect the most vulnerable.