Subjects are eligible for the study if all of the following apply: Willing to receive routine COVID-19 vaccination with Pfizer, Moderna or AstraZeneca vaccine. Age: ≥16 years or <16 years once vaccine is recommended for routine use in this age group Either Down syndrome or household contacts without Down syndrome of participant with Down syndrome

Subjects are eligible for the study if all of the following apply: Willing to receive routine COVID-19 vaccination with Pfizer, Moderna or AstraZeneca vaccine. Age: ≥16 years or <16 years once vaccine is recommended for routine use in this age group Either Down syndrome or household contacts without Down syndrome of participant with Down syndrome