Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of mRNA-1944 in Healthy Adults

Inclusion Criteria: * Male or female ≥ 18 and ≤ 50 years of age * Weight of 50 to 100 kg, inclusive * In good general health as determined by medical history, clinical laboratory assessments, ECG results, vital sign measurements, and physical examination findings at screening * Has access to consistent and reliable means of contact and agrees to stay in contact with the study site for the duration of the study Exclusion Criteria: * Any acute or chronic clinically significant disease, as determined by physical examination or laboratory screening tests * Elevated liver function tests or safety laboratory test results * Positive screening test for the presence of anti-CHIKV IgG * Administration of another investigational study involving any investigational product within 60 days or 5 half-lives, whichever is longer * Has received any live attenuated or inactive vaccines within 4 weeks prior to check-in, or plans to receive any vaccine during the study * Known or suspected immune-mediated disease or immunosuppressive condition (including lymphoproliferative disorders) * Any neurologic disorder * History of idiopathic urticaria * Any bleeding disorder that is considered a contraindication to study drug infusion or blood collection * Receipt of immunoglobulins, a monoclonal antibody or any blood products within the preceding 6 months * Any acute illness at the time of enrollment * A positive test result for drugs of abuse * A positive test result for hepatitis B surface antigen, hepatitis C virus antibody, or human immunodeficiency virus type 1 or 2 antibodies * A history of active cancer (malignancy) in the last 3 years * Donation of ≥ 450 mL blood or blood products within 30 days of study drug infusion