Middlesex-London Health Unit - Walk-in Pop-Up Vaccination Clinics The clinics below are open to anyone 12 years of age and older to receive their first or second dose. No appointment is needed. If your 1st dose was Pfizer or Moderna, pick any date more than 28 days after your first dose. If your 1st dose was AstraZeneca, pick any date more than 8 weeks after your first dose. No health card is required.