4. Healthy as judged by the Investigator or designee and determined by complete general physical examination, vital signs, clinical laboratory tests, and medical history conducted no more than 30 days prior to study vaccine administration. Subjects with a pre-existing chronic disease will be allowed to participate if the disease is stable and, according to the Investigator's judgment, the condition is unlikely to confound the results of the study or pose additional risk to the subject by participating in the study. Stable disease is generally defined as no new onset of exacerbation of pre-existing chronic disease 6 months prior to immunization. Based on the Investigator's judgment, a subject with more recent stabilization of a disease could also be eligible.