Third dose

If you are eligible due to a medical condition that requires a doctor's referral or eligible prescription, you can get a third dose 8 weeks after your second. If you are eligible for another reason (e.g. 70+, healthcare workers) you can get a third dose 6 months (24 weeks, or 168 days) after your last dose. If you come to a clinic before enough time has passed since your second dose, you will not be able to proceed with the appointment. Check your eligibility with our third dose calculator.

Currently, two doses of a Health Canada approved vaccine (any combination of Astra Zeneca, Moderna and Pfizer) is considered by Ontario to be a complete COVID-19 vaccination series. You are considered fully vaccinated 14 days after your second dose at this time.

A third dose is an additional shot of vaccine that helps you maintain and lengthen your protection against COVID-19. When you get a third dose, you're helping protect you and the people around you from COVID-19. Third doses, or booster doses, are currently prioritized for those most at risk of serious illness from COVID-19 infection, including older adults and people with certain health conditions. At this time, only specific populations are eligible for third doses

The COVID-19 vaccines are safe and highly effective at preventing severe illness, hospitalization, and death from COVID-19, however protection may gradually decline over time. This lower effectiveness is likely due to the combination of decreasing protection as time passes since getting vaccinated, as well as the greater infectiousness of the Delta variant.

Learn more about third dose eligibility and guidance from the Ministry.

Vaccine dose calculator

Use the HPPH COVID-19 vaccine dose calculator to find out the earliest date you are eligible for your next dose of vaccine.

Vaccine dose calculator

Third dose eligibility

Please review the eligible groups below carefully. At this time, individuals who are eligible for a third dose are only able to book a third dose appointment based on the required interval between their second and third doses. Some groups (e.g. 70+, healthcare workers) are eligible six months after their second dose. Other groups, who are eligible due to specific medical conditions and treatments, are eligible as early as two months after their second dose.

Groups eligible as of November 3, 2021:

Based on the recommendation of the Chief Medical Officer of Health and in alignment with the National Advisory Committee on Immunization’s (NACI) recent recommendation, the province will begin offering booster doses of the COVID-19 vaccine to the following vulnerable populations if at least six months have passed since their last dose. 

People belonging to one of the following groups are eligible to receive a booster dose if at least six months (168 days minimum) have passed since their second dose:

  • Designated essential caregivers in congregate settings (including long-term care home and retirement home staff and designated caregivers);
  • Individuals who received a complete series of a viral vector vaccine (two doses of the AstraZeneca vaccine or one dose of the Janssen vaccine); and
  • First Nation, Inuit and Métis adults and their non-Indigenous household members.
*List of health care workers eligible for booster doses

Regulated health professionals and any staff member, contract worker, student/trainee, registered volunteer, or other designated essential caregivers currently working in-person in a health care organization, including workers that are not providing direct patient care and are frequently in the patient environment (i.e. cleaning staff, research staff, other administrative staff) are included in the below:

  • All hospital and acute care staff including:
    • Critical Care Units, Emergency Departments and Urgent Care Departments, COVID-19 Medical Units, Code Blue Teams, rapid response teams
    • General internal medicine and other specialists, Surgical care, Obstetrics
  • All patient-facing health care workers/staff involved in the COVID-19 response:
    • COVID-19 Specimen Collection Centers, COVID-19 Isolation Centers
    • Mobile Testing Teams, COVID-19 Laboratory Services, Teams supporting outbreak response (e.g., IPAC teams supporting outbreak management, inspectors in the patient environment)
    • COVID-19 vaccine clinics and mobile immunization teams
    • Current members of Ontario’s Emergency Medical Assistance Team (EMAT)
  • Medical First Responders (ORNGE, paramedics, firefighters providing medical first response, police and special constables providing medical first response as part of their regular duties).
  • Health care workers and designated essential caregivers in congregate settings (assisted living, correctional settings, shelters, LTCHs/RHs, supportive housing, hospices and palliative care settings, etc.)
  • Home and community health care workers, providing in-person care, including:
    • Needle exchange/syringe programs & supervised consumption and treatment services
    • Indigenous health care service providers including but not limited to: Aboriginal Health Access Centers, Indigenous Community Health Centers, Indigenous Interprofessional Primary Care Teams, and Indigenous Nurse Practitioner-Led Clinics
    • Community health centres, chronic homecare, birth centres, dentistry and dental hygiene, Pharmacies, Primary care, Walk-in clinics, gynecology/obstetrics, Midwifery, Nurse practitioner-led clinics/Contract nursing agencies, Otolaryngology (ENT), medical and surgical specialities, medical transport, laboratory services, independent health facilities, health care providers in developmental services, mental health and addictions services
    • Health care workers in schools/daycare/campus, sexual health clinics, community diagnostic imaging, dietary/nutrition, audiology, naturopathy, holistic care, chiropractic, chronic pain clinics, kinesiology/physiotherapy, occupational therapy, psychiatry, acupuncture, registered massage therapy, psychotherapy, social work, public health

Health conditions: Individuals who are immunocompromised 

Individuals with the following medical conditions who are considered at most risk of serious illness remain eligible for a third dose, at least 8 weeks after their second dose

Please note: before receiving your third dose you must speak with your healthcare provider.

  • Individuals receiving active treatment (e.g., chemotherapy, targeted therapies, immunotherapy) for solid tumour or hematologic malignancies.
  • Recipients of solid-organ transplant and taking immunosuppressive therapy.
  • Recipients of chimeric antigen receptor (CAR) T-cell therapy or hematopoietic stem cell transplant (within 2 years of transplantation or taking immunosuppression therapy).
  • Individuals with moderate to severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome).
  • Individuals with stage 3 or advanced untreated HIV infection and those with acquired immunodeficiency syndrome.
  • Individuals receiving active treatment with the following categories of immunosuppressive therapies: anti-B cell therapies (monoclonal antibodies targeting CD19, CD20 and CD22), high-dose systemic corticosteroids, alkylating agents, antimetabolites, or tumor-necrosis factor (TNF) inhibitors and other biologic agents that are significantly immunosuppressive.

Please speak with your healthcare provider about your third dose eligibility and to receive a referral form. Your healthcare provider will discuss administration timing of your third dose, in order to optimize the immune response from the vaccine series.

Long-term care and retirement homes

Third dose immunizations have been provided at all eligible Long-Term Care Homes and licensed Retirement Homes in Huron Perth.  Public Health Units are able to work with partner ministries to determine eligible senior congregate settings as well.

How to get your third dose if you are eligible

If you are eligible and meet the required time interval between doses, you can get your third dose through any of the following settings:

  • Your primary care provider
  • Select pharmacies: COVID-19 pharmacy vaccine locations
    • Please note that your treating healthcare provider will need to contact the pharmacy first if you are eligible for a third dose based on a medical condition. 
  • An HPPH vaccination clinic
    • Visit our Get a Vaccination page to book an appointment online, or call our booking line at 1-833-753-2098. 
    • Please note you will be required to provide documentation from your healthcare provider, or you will be asked to attest to your medical condition that makes you eligible and that you have received direction from your HCP to receive a third dose.

Timing with other vaccinations

COVID-19 vaccines can be given at the same time or any time before or after another vaccine. This means you do not have to worry about timing between your COVID-19 vaccination and other vaccines, like the influenza vaccine or other childhood immunizations.

Vaccine types

All third doses will be mRNA vaccines. You will receive either the Moderna or Pfizer (mRNA) vaccine for your third dose. These vaccines are interchangeable. If you received AstraZeneca for your first or second dose, you will receive Moderna or Pfizer for your third dose.

Vaccine side effects

There are no additional risks to getting a third dose. Overall most reported side effects have been mild to moderate. Common vaccine side effects may include redness, soreness and swelling at the injection site, chills, fatigue, joint pain, headache, mild fever, muscle aches. Serious side effects are rare but may occur.

For more information visit our About Vaccines page.