A potential subject who meets any of the following criteria will be excluded from participation in this study: Down syndrome cohort History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (e.g. anaphylaxis) to any component of the study intervention(s). Organ transplant recipients Active malignancy or completion of treatment for malignancy in previous 3 months Infection with Human Immunodeficiency Virus (HIV) Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection. Healthy control cohort As in Down Syndrome cohort Plus Active medical care for inherited or acquired immune deficiency Any severe comorbidity for which regular medical care is needed (e.g. heart failure, COPD, diabetes)

A potential subject who meets any of the following criteria will be excluded from participation in this study: Down syndrome cohort History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (e.g. anaphylaxis) to any component of the study intervention(s). Organ transplant recipients Active malignancy or completion of treatment for malignancy in previous 3 months Infection with Human Immunodeficiency Virus (HIV) Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection. Healthy control cohort As in Down Syndrome cohort Plus Active medical care for inherited or acquired immune deficiency Any severe comorbidity for which regular medical care is needed (e.g. heart failure, COPD, diabetes)