Age and Sex: 1. Male or female participants ≥6 months to <12 years of age, at the time of randomization, at Visit 1. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.

Age and Sex: 1. Male or female participants ≥6 months to <12 years of age, at the time of randomization, at Visit 1. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.

Age and Sex: 1. Male or female participants between ≥6 months and <12 years of age, at the time of randomization, at Visit 1 for the dose finding/selecteddose evaluation and between ≥5 and <30 years of age, at the time of randomization, at Visit 1 for the lower-dose evaluation. For the obtaining-serum samples-for-potential-troponin I testing portion of the study: Male or female participants between ≥5 and <16 years of age. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant or participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant or participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.

Age and Sex: 1. Male or female participants between ≥6 months and <12 years of age, at the time of randomization, at Visit 1 for the dose finding/selecteddose evaluation and between ≥5 and <30 years of age, at the time of randomization, at Visit 1 for the lower-dose evaluation. For the obtaining-serum samples-for-potential-troponin I testing portion of the study: Male or female participants between ≥5 and <16 years of age. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant or participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant or participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.

Age and Sex: 1. Male or female participants ≥6 months to <12 years of age, at the time of randomization, at Visit 1. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.

Age and Sex: 1. Male or female participants ≥6 months to <12 years of age, at the time of randomization, at Visit 1. Refer to Appendix 4 for reproductive criteria for male (Section 10.4.1) and female (Section 10.4.2) participants. Type of Participant and Disease Characteristics: 2. Participants’ parent(s)/legal guardian(s) and participants, as age appropriate, who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. 3. Healthy participants who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study. Note: Healthy participants with preexisting stable disease, defined as disease not requiring significant change in the therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included. Phase 2/3: Specific criteria for such participants with known stable infection with HIV, HCV, or HBV can be found in Section 10.7. 4. Participants are expected to be available for the duration of the study and whose parent(s)/legal guardian can be contacted by telephone during study participation. 5. Negative urine pregnancy test for female participants who are biologically capable of having children. 6. Female participant of childbearing potential or male participant able to father children who is willing to use a highly effective method of contraception as outlined in this protocol for at least 28 days after the last dose of study intervention if at risk of pregnancy with her/his partner, or female participant not of childbearing potential or male participant not able to father children. Informed Consent: 7. The participant’s parent(s)/legal guardian is capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the ICD and in this protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written). The investigator, or a person designated by the investigator, will obtain written or electronically signed informed consent (and assent) from each study participant’s legal guardian (as defined in Appendix 1) and the participant’s assent, when applicable, before any study-specific activity is performed. All legal guardians should be fully informed, and participants should be informed to the fullest extent possible, about the study in language and terms they are able to understand. The investigator will retain the original copy of each participant's signed consent/assent document.