U.S. Navy Hospital Corpsman 1st Class Ernesto Santa Ana, with the Naval Medical Research Center, collects blood samples from a Marine participant with the COVID-19 Health Action Response for Marines (CHARM) study on Camp Johnson, N.C., Mar. 3, 2021. - U.S. Navy Hospital Corpsman 1st Class Ernesto Santa Ana, with the Naval Medical Research Center, collects blood samples from a Marine participant with the COVID-19 Health Action Response for Marines (CHARM) study on Camp Johnson, N.C., Mar. 3, 2021.