Pfizer vaccine available for individuals 12 years and older. Second dose Pfizer should be given at 21 days after first shot, but may be given as early as 17 days. Immunocompromised individuals should consult their doctor to confirm their eligibility for a third dose. Third dose for immunocompromised should not be given earlier than 28 days after the second dose. Booster dose for 65 and over or high risk populations should be given no earlier than 6 months after second dose