Inclusion Criteria:  18 years of age or older. Ability to provide informed consent. Enrollment within one day (before or after) of receipt of COVID-19 vaccine. Willingness to be evaluated (including collection of blood and nasopharyngeal samples) during the prescribed study visits and/or during acute illness consistent with SARS-CoV-2 infection during the study period. Willingness to allow storage of biological samples for research testing as outlined in this protocol.  Exclusion Criteria:  Any acute or chronic condition that, in the opinion of the investigator, is a contraindication to participation in this study; for example, acute febrile illness. Inability to comply with study visits.