Burden of PCR-Confirmed SARS-CoV-2 Reinfection in the U.S. Veterans Administration, March 2020 - January 2022

An essential precondition for successful "herd immunity" strategies for the control of SARS-CoV-2 is that reinfection with the virus be relatively rare. Some infection control, prioritization, and testing strategies for SARS-CoV-2 were designed on the premise of rare re-infection. The U.S. Veterans Health Administration (VHA) includes 171 medical centers and 1,112 outpatient sites of care, with widespread SARS-CoV-2 test availability. We used the VHAs unified, longitudinal electronic health record to measure the frequency of re-infection with SARS-CoV-2 at least 90 days after initial diagnosis We identified 308,051 initial cases of SARS-CoV-2 infection diagnosed in VHA between March 2020 and January 2022; 58,456 (19.0%) were associated with VHA hospitalizations. A second PCR-positive test occurred in 9,203 patients in VA at least 90-days after their first positive test in VHA; 1,562 (17.0%) were associated with VHA hospitalizations. An additional 189 cases were identified as PCR-positive a third time at least 90-days after their second PCR-positive infection in VHA; 49 (25.9%) were associated with VHA hospitalizations. The absolute number of re-infections increased from less than 500 per month through November 2021, to over 4,000 per month in January 2022.