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Second Dose Interval - Highest-risk health conditions

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COVID-19 Vaccination Clinic

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Special Considerations on Second Dose Intervals

For individuals with highest-risk health conditions, only the following highest-risk populations are eligible to receive the COVID-19 vaccine at the shortened dose interval of 28 days (for both Moderna and Pfizer-BioNTech COVID-19 Vaccines) or 12 weeks for AstraZeneca.

  • Transplant recipients (including solid organ transplants and hematopoietic stem cell transplants)
  • Individuals undergoing hemodialysis or peritoneal dialysis
  • Individuals with malignant hematologic disorders and non-hematologic malignant solid tumors receiving active treatment (chemotherapy, targeted therapies, immunotherapy) excluding individuals receiving solely hormonal therapy or radiation therapy
  • Those taking anti-CD20 agent medication (for example, rituximab, ocrelizumab, ofatumumab)

Essential caregivers will not be eligible for the shortened second dose interval. 

This patient group will require a letter or form from their clinician to confirm that they are eligible to receive a second dose appointment at the 28-day interval, identifying the reason for exception. The letter or form should be presented at both the first and second appointments to confirm that they are eligible to get a second dose appointment at the shortened dose interval.

If you have already received a first dose of COVID-19 vaccine, then you must provide your clinician with the proof of vaccination slip. Individuals will need to receive the second dose of the same COVID-19 vaccine received at first dose.

Patients who have scheduled 1st vaccination in Ministry Vaccination Tool who are required to change 2nd dose to 28 day interval

Please follow these instructions

If the patient has already received a first dose of COVID-19 vaccine, the patient must provide their clinician with their proof of vaccination slip to complete this form. This form (or similar letter from the clinician) must be presented at their second dose appointment to confirm eligibility for second dose at the 28-day interval. Patients must contact the hospital, pharmacy, or Public Health Unit where they received their first dose to arrange their second dose at the shorter interval and will need to receive the same COVID-19 vaccine received at first dose.

  • Niagara Health (905-378-4647, Ext. 49099) for vaccination at Seymour-Hannah Sports and Entertainment Centre
  • Niagara Region Public Health (905-688-8248, press 7 then press 2) for all Public Health clinic locations


Niagara Health System