EPICC (Epidemiology, Immunology, and Clinical Characteristics of Emerging Infectious Diseases with Pandemic Potential) Study. The overall study is available to adult (≥18 years old) DoD active and non-active duty service members and beneficiaries who are eligible to receive care in the MHS and either meet criteria to be tested for COVID-19 or have received a vaccine for COVID-19. You may only participate in this cognitive assessment sub-study if you are enrolled in the main study, have met sub-study eligibility, and have consented to participate.