You have to be at least 18 years old for the Moderna study and I couldn't find an upper limit. The AstraZeneca study allows subjects as young as 5 yrs old.
Randomization will be stratified based on age and, if they are < 65 years of age, based on the presence or absence of risk factors for severe illness from COVID-19 based on CDC recommendation as of Mar 2020. There will be 3 strata for randomization: ≥ 65 years, < 65 years and categorized to be at increased risk (“at risk”) for the complications of COVID-19, and < 65 years “not at risk”. Risk will be defined based on the study participants’ relevant past and current medical history. At least 25% of enrolled participants, but not more than 40%, will be either ≥ 65 years of age or < 65 years of age and “at risk” at Screening.
Participants who are < 65 years old will be categorized as at risk for severe COVID-19 illness if they have at least 1 of the following risk factors at Screening:
Chronic lung disease (eg, emphysema and chronic bronchitis, idiopathic pulmonary fibrosis, and cystic fibrosis) or moderate to severe asthma
Significant cardiac disease (eg, heart failure, coronary artery disease, congenital heart disease, cardiomyopathies, and pulmonary hypertension)
Severe obesity (body mass index ≥ 40 kg/m2)
Diabetes (Type 1, Type 2 or gestational)
Liver disease
Human Immunodeficiency Virus (HIV) infection