We plan to recruit 130 non-pregnant subjects including Health Care Workers, which refer to anyone who works in the hospital, into each active arm and 65 healthy, non-pregnant subjects including Health Care Workers into each placebo arm for a total of 390 study subjects from 4 study sites in Bangkok and Nonthaburi province, Thailand: (i) Faculty of Medicine Siriraj Hospital, (ii) Bamrasnaradura Infectious Diseases Institute, (iii) Chest Disease Institute, and (iv) Hospital for Tropical Diseases.