The primary series for those with health immune systems:
Pfizer is a two dose series, spaced at least 21 days apart
Moderna is a two dose series, spaced at least 28 days apart
J&J is a single dose
The primary series for those who are moderately to severely immunocompromised is a 3 dose series:
Pfizer is a 3 dose series. 21 days between dose 1 and dose 2; and 28 days between dose 2 and dose 3
Moderna is a 3 dose series. 28 days between each dose