Patient Inclusion Criteria

Inclusion - 18 to 49 years of age - Body mass index between 18 and 35 kg/m2 - In good health as determined by medical history - Female subjects must be non pregnant and non lactating and meet one of the following criteria: a) post menopausal b) surgically sterile - Women of childbearing potential must agree to be heterosexually inactive or agree to consistently use any of the following methods of contraception from at least 21 days prior to enrollment and through 3 months after the final vaccination - Male subjects must use an acceptable method of birth control throughout the entire study and agree to refrain from donation of sperm from the time of first vaccination until 3 months following the last vaccination - Agrees to comply with the study procedures and provides written informed consent - Has access to a consistent and reliable means of telephone contact and agrees to stay in contact with the study site for the duration of the study, to provide updated contact information as necessary, and has no current plans to move from the study area for the duration of the study Exclusion - Any ongoing, symptomatic acute or chronic illness requiring medical or surgical care - A history of active cancer (malignancy) in the last 10 years - Female of childbearing potential and has a positive pregnancy test at screening or on the day of vaccination - Administration of an investigational product within 60 days, or 5 half-lives, whichever is longer - Administration of any live attenuated vaccines within 4 weeks before enrollment or inactive vaccines within 2 weeks before enrollment, or plans to receive any vaccine during the active vaccination period - Prior administration of a vaccine for Zika or dengue vaccine, a history of confirmed Zika or dengue infection, or has lived in or visited any Zika-endemic area greater than 4 weeks in duration - Prior administration of investigational agent using formulations similar to mRNA-1325 - A history of hypersensitivity or serious reactions to previous vaccinations - Any known or suspected autoimmune disease or immunosuppressive condition, acquired or congenital, as determined by medical history and/or physical examination - A history of inflammatory arthritis - Any neurologic disorder - A history of febrile disease with arthritis or arthralgia within 2 weeks of dose administration. - Prior administration of immunoglobulins and/or any blood products within the 3 months preceding the administration of the study drug or plans to receive such products at any time during the study - Any chronic administration of an immunosuppressant or other immune modifying drug - Any acute illness at the time of enrollment - Any significant disorder of coagulation requiring ongoing or intermittent treatment - A history of idiopathic urticaria - A history of alcohol abuse or drug addiction - A positive test result for drugs of abuse - The subject has any abnormality or permanent body art (eg, tattoo) that, in the opinion of the investigator, would obstruct the ability to observe local reactions at the injection site - Any condition that, in the opinion of the investigator, would pose a health risk to the subject if enrolled or could interfere with evaluation of the study drug or interpretation of study results - A positive test result for hepatitis B surface antigen, hepatitis C virus antibody, or human immunodeficiency virus types 1 or 2 antibodies - Donation of blood or blood products > 450 mL within 30 days of dosing. - Abnormal vital signs or screening safety laboratory test results including liver enzyme tests - Is an employee or first degree relative of the Sponsor, CRO, or study site personnel

Patient Exclusion Criteria

Inclusion - 18 to 49 years of age - Body mass index between 18 and 35 kg/m2 - In good health as determined by medical history - Female subjects must be non pregnant and non lactating and meet one of the following criteria: a) post menopausal b) surgically sterile - Women of childbearing potential must agree to be heterosexually inactive or agree to consistently use any of the following methods of contraception from at least 21 days prior to enrollment and through 3 months after the final vaccination - Male subjects must use an acceptable method of birth control throughout the entire study and agree to refrain from donation of sperm from the time of first vaccination until 3 months following the last vaccination - Agrees to comply with the study procedures and provides written informed consent - Has access to a consistent and reliable means of telephone contact and agrees to stay in contact with the study site for the duration of the study, to provide updated contact information as necessary, and has no current plans to move from the study area for the duration of the study Exclusion - Any ongoing, symptomatic acute or chronic illness requiring medical or surgical care - A history of active cancer (malignancy) in the last 10 years - Female of childbearing potential and has a positive pregnancy test at screening or on the day of vaccination - Administration of an investigational product within 60 days, or 5 half-lives, whichever is longer - Administration of any live attenuated vaccines within 4 weeks before enrollment or inactive vaccines within 2 weeks before enrollment, or plans to receive any vaccine during the active vaccination period - Prior administration of a vaccine for Zika or dengue vaccine, a history of confirmed Zika or dengue infection, or has lived in or visited any Zika-endemic area greater than 4 weeks in duration - Prior administration of investigational agent using formulations similar to mRNA-1325 - A history of hypersensitivity or serious reactions to previous vaccinations - Any known or suspected autoimmune disease or immunosuppressive condition, acquired or congenital, as determined by medical history and/or physical examination - A history of inflammatory arthritis - Any neurologic disorder - A history of febrile disease with arthritis or arthralgia within 2 weeks of dose administration. - Prior administration of immunoglobulins and/or any blood products within the 3 months preceding the administration of the study drug or plans to receive such products at any time during the study - Any chronic administration of an immunosuppressant or other immune modifying drug - Any acute illness at the time of enrollment - Any significant disorder of coagulation requiring ongoing or intermittent treatment - A history of idiopathic urticaria - A history of alcohol abuse or drug addiction - A positive test result for drugs of abuse - The subject has any abnormality or permanent body art (eg, tattoo) that, in the opinion of the investigator, would obstruct the ability to observe local reactions at the injection site - Any condition that, in the opinion of the investigator, would pose a health risk to the subject if enrolled or could interfere with evaluation of the study drug or interpretation of study results - A positive test result for hepatitis B surface antigen, hepatitis C virus antibody, or human immunodeficiency virus types 1 or 2 antibodies - Donation of blood or blood products > 450 mL within 30 days of dosing. - Abnormal vital signs or screening safety laboratory test results including liver enzyme tests - Is an employee or first degree relative of the Sponsor, CRO, or study site personnel