The objective of this contract is to develop infrastructure to collect data of various types and from various sources in order to perform critical analyses using an integrated set of linked data representing commercial longitudinal laboratory test results at the patient level for SARS CoV-2 Nucleic Acid Amplification Test (NAAT) and antibody testing to assess the impact of known SARS-CoV-2 seropositivity on the rate of subsequent re-infection with a cohort study design using Real World Data (RWD). The data will be analyzed to determine whether antibodies to SARS-CoV-2 are protective against re-infection, and if so, how long that protection last. While vaccine-related clinical trials are underway, results are likely to be slower than potential analyses using RWD. The cohort is defined as all patients tested for SARS-CoV-2 antibodies that can be followed longitudinally (for a minimum of one year). The longitudinal analysis will be conducted using data from commercial lab test results linked to data (beginning with data pulled from January 2020 through present with monthly downloads to the Government for the Period of Performance over four months) from claims for inpatient, outpatient and pharmacy data, hospital chargemaster data representing detailed services received during an inpatient hospital admission, and EMR data from outpatient facilities both integrated with a health care system as well as for community practices.