To further increase COVID-19 vaccination rates, City of Hamilton Public Health Services has launched the Ask at Every Visit: Minimal Contact COVID-19 Vaccine Intervention. Below are resources provided to support health professionals in asking clients about their vaccination status, employing the Ask-Advise-Assess-Assist model.

In addition to the resources from Public Health, Dr. Kati Ivanyi has prepared an email message for primary care practices. Please feel free to use or adapt as you see fit:

For further reference, please see Public Health Services policy for Ask at Every Visit: Minimal Contact COVID-19 Vaccine Intervention

The Ontario Ministry of Health has prepared a fact sheet about vaccine interchangeability.

A Safe and Effective Second Dose (English) June 21, 2021

Une seconde dose sécuritaire et efficace (French) June 21, 2021

NACI made a statement on June 1 regarding interchangeability of vaccines. This may be of particular interest to patients who have received the AstraZeneca vaccine for their first dose and may have concerns about the second.

Interchangeability of Authorized COVID-19 Vaccines
From the Public Health Agency of Canada
June 1, 2021


  • The Public Health Agency of Canada released, on June 1st, 2021, updated recommendations from the National Advisory Committee on Immunization (NACI) on the interchangeability of authorized COVID-19 vaccines (also referred to as ‘mixed vaccine schedules’). These recommendations are based on current scientific evidence and NACI’s expert opinion.
  • The interchangeability of vaccines means you could receive one vaccine product for your first dose and a different vaccine product for your second dose to complete your two-dose vaccine series.
  • With first doses well underway, provinces and territories are now accelerating the offer of second doses of COVID-19 vaccines. NACI’s advice on mixed vaccine schedules provides provinces and territories with options to manage their COVID-19 vaccine programs.
  • NACI recommends that:
    • Persons who received a first dose of the AstraZeneca/COVISHIELD vaccine may receive either AstraZeneca/COVISHIELD vaccine or an mRNA vaccine (Pfizer-BioNTech or Moderna) for their second dose, unless contraindicated.
    • Persons who received a first dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) should be offered the same mRNA vaccine for their second dose. If the same mRNA vaccine is not readily available or unknown, another mRNA vaccine can be considered interchangeable and should be offered to complete the vaccine series.
  • In making their recommendation to offer mRNA as the second dose following a first dose of AstraZeneca/COVIDSHIELD, NACI considered:
    • The risk of severe blood clots with low blood platelets associated with the AstraZeneca viral vector vaccine but not the mRNA (Pfizer-BioNTech or Moderna) vaccines;
    • The possibility of increased short-term side effects when using mixed COVID-19 vaccine schedules; and
    • Available data on the immune responses produced by a first dose of the AstraZeneca vaccine followed by a second dose of the Pfizer-BioNTech vaccine.

To see the Rapid Response, please visit NACI rapid response: Interchangeability of COVID-19 vaccines.


  • This is not a new concept. Similar vaccines from different manufacturers are used when vaccine supply or public health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others.
  • mRNA and AstraZeneca/COVISHIELD vaccines are both available in Canada and there will be sufficient supply of both types of vaccine to provide second doses. Getting the same vaccine for the first and second dose or a mixed schedule are both considered valid options, and both will count as a completed series. Individuals should consider talking to a healthcare professional for help with understanding information to support informed individual decision-making on vaccination.
  • Severe blood clots with low blood platelets, a condition referred to as Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT), has been associated with the use of viral vector vaccines (AstraZeneca/COVISHIELD, Janssen). Because of this rare but serious adverse event, several European countries, including Denmark, Finland, France, Germany, Norway, Spain and Sweden, began offering a second dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) to those who received a first dose of the AstraZeneca/COVISHIELD viral vector vaccine.
  • Recent studies on the safety of and one study on the immune responses produced using mixed COVID-19 vaccine schedules provide the evidence for vaccine interchangeability – a study from Germany and a clinical trial from the United Kingdom report on the safety of mixed schedules, and a Spanish trial reports both the safety and immune responses produced from mixed COVID-19 vaccine schedules.
    • Current evidence suggests a first dose of the AstraZeneca vaccine followed by a second dose of mRNA vaccine (Pfizer-BioNTech was used in studies) has a good safety profile at shorter (4-week) and longer (8- to 12-week) intervals.
    • There is a possibility of increased short-term side effects when using mixed COVID-19 vaccine schedules, including headache, fatigue and feeling generally ill. This was particularly noted with a short interval of 4 weeks between the first and second dose. These side effects are temporary and resolve without complications.
    • The rate of VITT after the second dose of AstraZeneca/COVISHIELD vaccine appears to be lower than with the first dose but has increased over time, with current estimates of approximately 1 per 600,000 people vaccinated.
    • There is evidence that providing an mRNA vaccine after AstraZeneca vaccine will boost the immune response, which is what we expect from a second dose.
    • More results from ongoing studies, including Canadian data, on using mixed COVID-19 vaccine schedules are expected in the coming months. NACI continues to closely monitor evolving evidence on mixed COVID-19 vaccine schedules and will update recommendations as needed.

Download the full PDF from PHAC.

For the latest information on clotting risk (VITP) and AstraZeneca vaccine from Canadian Science Table. See summary of key points in “Adverse Reactions” section and full link to science table evidence summary May 10 2021 here.

Vaccines at a glance

From the Centre for Effective Practice
Version 2.0 Mar 18, 2021

More in-depth information on each topic below table.

Updated information is highlighted.

Pfizer Moderna AstraZeneca Janssen (J & J)
Trial efficacy Overall efficacy rate (clinical trial data) 95.00% 94.10% 59.90% 66.90%
Efficacy rate against severe disease >1-14 days after dose 2: 75-100% 14 days after dose 2: 100% After dose 2: 100% 28 days after dose: 85.4%
Number of trial participants who developed severe disease 1 vaccine/9 placebo 0 vaccine/30 placebo 0 vaccine/8 placebo 4 weeks after: 5 vaccine/34 placebo
Variants Against variants without E484K mutation (higher transmission) Likely similar to overall Likely similar to overall Likely similar to overall Unknown
Against variants with E484K mutation (higher transmission, increased severity) Likely reduced Likely reduced Likely reduced Likely reduced
Variant-specific vaccine development underway Y Y Y Y
Type Type mRNA mRNA Viral vector Viral vector
Contain live virus? N N N N
Ethics Tested in diverse racial/ethnic populations? Y Y Y Y
Admin Number of shots 2 2 2 1
Minimum interval between shots 21 days 28 days 12 weeks
Specific pops Children 12-15* 16-18 N N
Adults > 65 Y Y Y Y
Pregnant/breastfeeding Y Y Y Y
Immunocompromised Y Y Y Y
AEFI Rate of serious adverse events in Canada 0.009% 0.009% Pending Pending
Common side effects** Pain at injection site Y Y Y Y
Fatigue Y Y Y Y
Headache Y Y Y Y
Muscle pain Y Y Y Y
Chills Y Y Y Y
Joint pain Y Y Y Y
Fever Y Y Y Y
Nausea, vomiting or diarrhea N N Y Y (nausea)

Vaccines in depth

Trial efficacy Due to the difference in efficacy between vaccines, some are asking if it’s possible to get the AZ/Janssen vaccine first, and then a ‘booster shot’ with an mRNA vaccine at a later date. We don’t know yet what the effect of a “mix and match” approach would be. It’s not recommended right now, as the effect on safety and efficacy of immune protection is unknown. We’ll keep you updated at Vaccine Emerging Evidence (CEP)
Variants Research is ongoing into the effect of the vaccines against the variants. Janssen’s clinical trial was the only one that included an assessment of efficacy against certain variants, and then only against moderate to severe disease. Other studies are testing antibodies taken from vaccine recipients to determine their ability to neutralize synthetic spike proteins. However, neutralization studies may not be an accurate proxy for vaccine efficacy: it is possible for a person with a reduced neutralizing antibody response to be fully immune. We will not know how effective the other vaccines are against the variants until more research is done. For study details and updates, see Emerging Evidence: Vaccines and variants (CEP)
Type As none of the vaccines contain live virus, reassure patients that they cannot cause COVID-19. For more information about how the vaccines work, see Types of COVID-19 Vaccines (CEP), and for more answers to patient questions about the vaccines, see Ensuring Patient Confidence in Vaccines (CEP)
Ethics One contributor to low vaccine confidence in BIPOC communities is the historic exclusion of these communities from medical research – or the inclusion without informed consent. It’s important that each vaccine trial included consenting participants of diverse racial and ethnic backgrounds. For more resources on understanding vaccine confidence in BIPOC communities, see Ensuring Patient Confidence in Vaccines (CEP)
Admin The dosage interval for each vaccine is a minimum interval. In order to vaccinate as many people as possible with a first dose, a recent recommendation from NACI encourages extending the interval to as long as four months between doses. For more information, see Vaccine Administration (CEP)
*To receive the Pfizer vaccine, children 12-15 must meet certain criteria including high risk for severe COVID-19. Studies on vaccine efficacy in children as young as 6 months are currently underway. See “Do the vaccines work in children?” (CEP)
Pregnant/breastfeeding individuals can receive the vaccine with informed consent. For more information see Emerging Evidence: Pregnant and breastfeeding individuals (CEP) Immunocompromised can receive the vaccine with informed consent. For more information see Emerging Evidence: Immunocompromised populations
AEFI After delaying use, the European Medicines Agency declared the AZ vaccine safe to use. Analysis of ~17 million doses found the rate of blood clots after taking the AZ vaccine was the same as the rate in the general public. Allergies: CSACI identifies the risk for serious allergic reaction for all vaccines as low. For more information, including who should see an allergist before vaccination, see Emerging evidence: Adverse events (CEP)
Share our patient after-care guide, including how to treat side effects: CEP After-care sheet (color); CEP After-care sheet (greyscale)
**Some patients given the Moderna vaccine may experience delayed localized injection site reactions ~8 days post vaccination including erythema, induration, and tenderness. These typically resolve within 4 to 5 days without the use of antibiotics. See Emerging evidence: Adverse events (CEP)

For more detailed information about side effects for each vaccine, see Pfizer, Moderna, AstraZeneca and Janssen (CEP)

Download pdf from the Centre for Effective Practice.

The OCFP have provided a really useful summary of guidance on vaccines and special populations for family physicians:

The OCFP has compiled current recommendations from various specialty groups to help guide vaccine discussions and decisions with special populations – such as those at risk of serious illness from COVID-19, as well as those groups excluded from clinical trials. Our thanks to Dr. Zainab Abdurrahman, Pediatric and Adult Allergist, and Pediatric Immunologist, for her input and review of this material.

Also see: COVID-19 Vaccines FAQs for Family Physicians (OCFP, April 1, 2021)

This information is specific to currently available mRNA vaccines: Pfizer-BioNTech and Moderna.

The Ministry of Health’s vaccination recommendations for special populations highlight the need for informed consent in certain populations, based on risk/benefit discussions.

The MOH pre-screening assessment tool and COVID-19 vaccine screening and consent form can help determine conditions and concerns prior to vaccination.

Who should not be vaccinated

  • People who have ever had a severe allergic reaction (i.e., anaphylaxis) to a previous dose of an mRNA COVID-19 vaccine or any of its ingredients should not receive the vaccine.
  • As a precautionary measure, acutely ill people should not receive the vaccine.
  • Individuals with symptoms of confirmed or suspected COVID-19 infection should defer vaccination until recovered.
  • Individuals who have received another vaccine in the past 14 days should not receive the vaccine.
  • Updated guidance (page 6) states the Pfizer-BioNTech vaccine may be offered to individuals 12 to 15 years of age who are at very high risk of severe outcomes of COVID19 and/or are at increased risk of exposure.

Current Information about Dose Interval and Exemptions for Highest Risk Conditions

The OCFP summarises the new guidance on dose intervals:

Given limited real-world data, in recommending the extended interval NACI says it looked at evidence from studies on efficacy and effectiveness of the vaccines in preventing outcomes such as infection, symptomatic disease, hospitalizations and death from COVID-19 and that “short term sustained protection is consistent with immunological principles and vaccine science”. The objective in giving up a short-interval second dose is to allow additional people to be vaccinated and potentially save a life or avoid hospitalization.

The Vaccine Clinical Advisory Group (VCAG) (March 26, 2021) has recommended two exceptions to the extended dose interval:

  1. Transplant recipients (including solid organ transplants and hematopoietic stem cell transplants)
  2. Those with malignant hematologic disorders and non-hematologic malignant solid tumors receiving active treatment (chemotherapy, targeted therapies, immunotherapy) or diagnosed less than a year ago.
  3. People with neurologic disorders in which respiratory function may be compromised  (eg MND, myasthenia gravis, MS)
  4. Kidney disease with eGFR <30
  5. One essential caregiver for any individual in the above group

Based on research around timing of immunization and immune response, these individuals are recommended to follow the dosing intervals in the product monographs. The VCAG has said it will continue to evaluate the recommended 16-week interval for the elderly and pregnant women.

See guide to vaccination clinic process for these patients.

Vaccine Clinical Advisory Group (VCAG) Recommendations on Exceptions to Extended Dose Intervals for COVID-19 vaccines. (Ministry of Health)

Other Timing Dosing FAQs

Q. How long should a patient wait after and before another vaccine before getting the COVID-19 vaccine? A waiting period after or before getting another type of vaccine is recommended so that any side effects from one vaccine are not confused with side effects of another. The recommendation is to wait 14 days after receiving another vaccine, and 28 days before giving another vaccine.

Q. What is the best timing for the COVID-19 vaccine around routine allergy shots or immunization of allergen immunotherapy? Allergy shots are not vaccines. There is no definitive guideline but most allergists advise to avoid the shots on the same day, and the American Academy of Allergy, Asthma and Immunology recommends a 48-hour interval between shots, so that immediate or delayed reactions to either injection can be monitored.

Q. How long after having had COVID-19 can one get the vaccine? Patients who are acutely ill should not get the vaccine. The current recommendation is that “people with current infection should wait until they have recovered from the acute illness and are eligible to discontinue isolation.”

Q. Should a patient who had COVID-19 previously still receive the full course of the two-dose vaccine (versus a single only)? For now, those who have previously had COVID should get a full course of the vaccine. It is still uncertain how long antibodies last.

Special Populations

Allergic reaction to previous dose or component of the vaccine: Patients who have had a severe allergy/anaphylaxis to a previous dose or any component of the vaccine and those who have an allergic reaction within 4 hours of receiving a previous dose of the vaccine or any of its components need written documentation of counselling, including a vaccination plan from an allergist / immunologist.

As needed for your patients, you can use eConsult for COVID-19 vaccine allergy related consultations, or refer your patient to this list of allergists / immunologists prepared by the MOH

The Canadian Society of Allergy and Clinical Immunology identifies the risk for serious allergic reaction as low and states, “the majority of individuals with a history of allergy will be able to safely receive vaccination for COVID-19”. This includes those with a history of serious allergic reactions or anaphylaxis to substances that are not an ingredient in this vaccine, and those with food allergy, eczema, allergic rhinitis (hayfever), asthma, or stinging insect allergy.

An extended period of observation of 30 minutes post vaccination is recommended for individuals with a history of severe allergic reaction (i.e., anaphylaxis) not related to vaccines or injectable medications.

Polyethylene glycol (PEG) has been identified as a potential allergen in the Pfizer-BioNTech vaccine but has not been confirmed as the cause of reaction for reported adverse reactions. PEG is found in many common over-the-counter medications (brand names Tylenol EZ tabs, Benadryl, Advil Liqui-gel and Reactine, for example) cosmetics and some food and drink; no cases of anaphylaxis to PEG in foods and drinks have been reported, according to the CSACI. People with a suspected hypersensitivity or who have had an immediate allergic reaction to PEG or polysorbate (the latter is not an ingredient in either vaccine but closely related to PEG) should not get either vaccine without being evaluated by an allergist-immunologist.

The Society of Obstetricians and Gynaecologists of Canada states that “the documented risk of not getting the COVID-19 vaccine outweighs the theorized and undescribed risk of being vaccinated during pregnancy or while breastfeeding and vaccination should be offered.” The MOH recommendations highlight that mRNA vaccines are not live vaccines are not expected to be a risk to the breastfeeding infant. This COVID-19 vaccine information sheet from Unity Health may be helpful as an aid for shared decision making with this population.

Verbal attestation by the patient of counselling by a healthcare provider familiar with the pregnancy must be documented before the vaccine is offered to a pregnant individual.

I am Pregnant or Breastfeeding. Should I get the COVID-19 Vaccine? (Provincial Council for Maternal and Child Health)

Cancer is a very broad and heterogenous set of diseases and cancer treatments also vary in terms of impact on the immune system. The Canadian Cancer Society has not yet released specific guidance on COVID-19 vaccines but addresses the question of immunization generally with this statement: “Talk to your doctor or health care team if you have questions about immunizations during or after cancer treatment. Avoid vaccinations if you are being treated for cancer. …. Inactivated vaccines don’t pose a safety risk but likely won’t work as well if your immune system isn’t working properly”.

For your patients with cancer, particularly if they are actively receiving cancer treatments, best to consult with their oncologist about risks/benefits of vaccination.

Specific immunosuppressed patients requiring verbal attestation that they have received counselling about risks benefits from their primary provider are those: receiving stem cell therapy, CAR-T therapy, chemotherapy, immune checkpoint inhibitors, monoclonal antibodies (e.g., rituximab) and other targeted agents (e.g., CD4/6 inhibitors, PARP inhibitors).

Children under the age of 18 (Moderna and AstraZeneca) and under the age of 16 (PfizerBioNTech) were not part of the original clinical trials. The Pfizer-BioNTech vaccine may be offered to individuals 12 to 15 years of age who are at very high risk of severe outcomes of COVID-19 (e.g., due to a pre-existing medical condition known to be associated with increased risk of hospitalization or mortality) AND/OR are at increased risk of exposure (e.g., due to living in a congregate care facility). Currently, Moderna is conducting trials in children age six months to 11 years, and Pfizer in children 12 to 15 years old; Johnson & Johnson has said it also plans to test in children.

Diabetes Canada “encourages people living with type 1 or type 2 diabetes to receive the COVID-19 vaccine when it is accessible and with consultation with your healthcare provider.” It notes that “adults with diabetes (type 1 and type 2) who contract COVID-19 are at greater risk of serious complications … and almost three times more likely to die in hospital.”

Toronto Centre for Liver Disease: “People living with liver disease are strongly encouraged to get vaccinated against COVID-19. This includes those with hepatitis B, hepatitis C, fatty liver, PBC, PSC, AIH, cirrhosis and other chronic liver diseases as well as those waiting for liver transplant and those who have already received a liver transplant.” 1

1 The OCFP thanks Dr. Hemant Shah, Director of Clinical Practice for Toronto Centre for Liver Disease – Francis Family Liver Clinic at UHN, for sharing this resource. The document is available in various languages on the clinic website.

“There is no reason to suspect that adverse events will be any different than in the general population” and the “potential benefits of vaccine likely outweigh theoretical risks.” (Canadian Society of Transplantation). CST also lists several recommendations for optimum vaccine efficacy.

Vaccination is recommended for high-risk rheumatology patients. Specifically, the Canadian Rheumatology Association states that people older than 70 should be considered for the vaccine regardless of the underlying condition, as should those who are at high risk for more severe illness, including those who are on corticosteroids. Those younger than 70 should be considered on a case-by-case basis and patients on DMARDs “do not appear to be at higher risk for more severe illness with COVID-19.”

Of note, there is currently no data to make a recommendation of whether DMARDs should be withheld during COVID-19 vaccination. Concerns for potential disease flare should be considered when making these decisions.

The American College of Rhuematology have provided a useful table of suggestions for withholding times for some DMARDs around vaccination: COVID-19 Vaccine Clinical Guidance Summary for Patients with Rheumatic and Musculoskeletal Diseases (American College of Rheumatology)

The Canadian Association of Gastroenterology endorses CDC guidelines for receiving the mRNA vaccines and makes its recommendations based on the “certainty of evidence”: in patients with IBD who are not on immunosuppression therapy, CAG recommends the vaccine be given; in patients who are on immunosuppression therapy, CAG suggests that vaccine be given.

Crohn’s and Colitis Canada notes the that non-live vaccines are widely recommended for immunocompromised individuals, including people with IBD on immunosuppressing medications. Its recommendation is that: “People with IBD, whether on immunosuppressive medications or not, should be offered the COVID-19 vaccine after informed consent,” and further noting, “Reduced effectiveness due to immune suppression is NOT a reason to avoid these COVID-19 vaccines.”

The Canadian Network of MS Clinics “feels strongly that immunization should be considered in all persons with MS”. Its guidance for people living with MS also states that people with progressive MS and others with MS and a higher risk for hospitalization due to COVID-19 should consider getting the vaccine as soon as it becomes available to them.

GBS is not contraindicated for COVID-19 vaccination, according to the GBS|CIDP Foundation. It points to the CDC statement that “persons who have previously had GBS may receive an mRNA COVID-19 vaccine.”

A small number of cases of Bell’s Palsy were reported in the Pfizer-BioNTech vaccine study but, as noted in this Ottawa Public Health patient FAQ and by others, a direct connection has not been established. The CDC notes also that the “Food and Drug Administration (FDA) does not consider these to be above the rate in the general population” and has not concluded these cases were caused by the vaccination. Individuals who previously had Bell’s Palsy may receive an mRNA COVID-19 vaccine.

This Neurology Today article offers a good summary of the current findings on MS, GBS and Bell’s Palsy.

The Platelet Disorder Support Association (PDSA) notes that the occurrence of severe thrombocytopenia in a person who received the vaccine is the “first such event reported after over 5 million vaccinations”, and that it is “uncertain whether the vaccination is causal or coincidental.” In summary, PDSA says the opinion of its medical advisors is: “our patients with ITP should not be hesitant to be vaccinated based on all available information.

We have also added the Thrombosis Society guidance on COVID-19 Vaccines and Anticoagulation. They emphasize that anticoagulant therapy should not be a barrier to the administration of the coronavirus vaccine and any bleeding risk due to anticoagulant therapy that may result in a hematoma (muscle bruise) at the vaccine injection site is greatly outweighed by the benefits of the vaccine.

For patients on warfarin:

  • We encourage patients who are receiving warfarin treatment to receive vaccinations, including the COVID-19 vaccine.
  • There is a small risk of bruising at the vaccination injection site, but we do not expect any serious effects related to being on blood thinning treatment.
  • We suggest that after the vaccine injection prolonged pressure for 3 to 5 minutes is applied to the injection site to reduce bruising.
  • There is no need to measure the blood thinning level (INR test) just before receiving a vaccination; you should continue INR testing according to the schedule recommended by your doctor.

For patients on a newer blood thinner, one of apixaban (Eliquis), dabigatran (Pradaxa), edoxaban (Lixiana), or rivaroxaban (Xarelto)

  • We encourage patients who are receiving blood thinning (anticoagulant) treatment to receive vaccinations, including the COVID-19 vaccine.
  • There is a small risk of bruising at the vaccination injection site, but we do not expect any serious effects related to being on blood thinning treatment.
  • We suggest that after the vaccine injection prolonged pressure for 3 to 5 minutes is applied to the injection site to reduce bruising.

For patients on aspirin or a similar drug because of a previous heart attack or stroke

  • We encourage patients who are receiving aspirin or similar drugs like clopidogrel (Plavix) or ticagrelor (Brillinta) to receive vaccinations, including the COVID-19 vaccine.
  • There is a small risk of bruising at the vaccination injection site, but we do not expect any serious effects related to being on blood thinning treatment.
  • We suggest that after the vaccine injection prolonged pressure for 3 to 5 minutes is applied to the injection site to reduce bruising.

COVID-19 vaccination and osteoporosis drug therapy (Recommendations from Osteoporosis Canada Rapid Response Team)

The AstraZeneca COVID-19 vaccine appears to be associated with autoimmune thrombosis that mimics heparin-induced thrombocytopenia.

The United Kingdom, European Union, and Scandinavian countries have reported rare cases of cerebral sinus vein thrombosis (CSVT) and thrombocytopenia in patients who received the AstraZeneca COVID-19 vaccine. The majority of affected patients thus far are women under the age of 55 years, and CSVT seems to occur 4 to 20 days after vaccination. The Paul Ehrlich Institute has demonstrated that affected individuals in Germany have antibodies that induce massive platelet activation, reducing the platelet count and causing thrombosis. This phenomenon mimics heparin-induced thrombocytopenia (HIT) yet it does not require heparin as a trigger. It has been named Vaccine-induced Thrombotic Thrombocytopenia (VITT).

To date, millions of AstraZeneca COVID-19 vaccine doses have been administered worldwide, with suspected cases of Vaccine-induced Thrombotic Thrombocytopenia (VITT) occurring in only a small fraction of vaccinated individuals. However, there is growing evidence of a causal link with the vaccine. The incidence of VITT appears to be between 1 in 125,000 and 1 in 1 million.

There is no evidence that the AstraZeneca COVID-19 vaccine increases the overall risk of thrombosis (e.g., deep vein thromboses, pulmonary emboli, myocardial infarction, stroke) beyond what is seen in the general population despite the observed increases in CSVT, as the risk of CSVT is orders of magnitude lower than the risk of other thromboses. The AstraZeneca COVID-19 vaccine is highly effective in preventing COVID-19, which also carries a high risk of thrombosis; 1 in 5 patients hospitalized with COVID-19 develops venous thrombosis.3 

At this time, it is not clear if certain patients are predisposed to VITT. The cases to date are predominantly in younger women, and so vaccines have been temporarily suspended in those under 55 in Canada.

Since VITTis immune-mediated, an individual with a thrombophilia, a family history of blood clots, or a personal history of arterial or venous clots would likely not be at increased of VITT. Accordingly, there are no new contraindications to receiving the AstraZeneca vaccine. 

Recognition, Diagnosis and Management of VITT

This is the Canadian Science Table Algorithm for VITT recognition and management.

Family Medicine’s role is to recognize the symptoms, check the timeframe criteria and then refer as CBC is needed in under 2 hours to support emergent pathway to treatment.

Read the Canadian Science Table Full Report here

AstraZeneca COVIShield Clotting Risk and Effectiveness Information (McMaster Family Health Team, updated April 26, 2021)

A summary report of COVID-19 vaccine adverse reactions in Canada is available weekly on the Public Health Ontario website.

To report an adverse event following COVID-19 vaccine

  1. Complete an AEFI Reporting Form
  2. Send it to your local public health unit

For Hamilton this is:
Fax: 905-546-4078
Hamilton Public Health Services
110 King St. West, 2nd Floor
Hamilton, ON  
L8P 4S6

There are Adverse Effects of Special Interest for COVID-19 vaccines that have been identified to date by the Public Health Agency of Canada and World Health Organization. (They are selected based on a theoretical rationale for a possible association with COVID-19 vaccines, not due to events or other findings from COVID-19 vaccine clinical trials.)

These include: Multisystem Inflammatory Syndrome in Children, Acute Respiratory Distress Syndrome,

Acute Cardiovascular Injury (esp. myocarditis, pericarditis), Coagulation Disorders, Acute Kidney Injury,

Acute Liver Injury, Anosmia and/or Ageusia, Chilblain – like Lesions, Single Organ Cutaneous Vasculitis, Erythema Multiforme, Vaccine-associated Enhanced Disease (A physician-diagnosed illness occurring in an individual who receives a vaccine and is subsequently infected with the pathogen that the vaccine is meant to protect against.)

More detail is provided here:

Adverse Events of Special Interest (Public Health Ontario Technical Brief)

Questions about COVID-19 vaccines?

There is also detailed information about specific vaccines for clinicians in the CEP link in the “other resources” tab in this section.

  • Patients should discuss any personal medical questions related to the vaccine with their health care provider ie. If they are unsure about their allergies, if they have autoimmune or immunosuppressed conditions, if they are pregnant, or who need to discuss getting the vaccine. (See the “Special Populations” tab in this vaccines section on hfam for resources for these discussions)

For patients asking how/when do I get the vaccine in Ontario?

  • Vaccines are being sequenced by the highest risk of contracting COVID-19, and guided by the Province. Information on when the next groups to be vaccinated in Hamilton and answers to frequently asked COVID vaccines questions is  available on City of Hamilton website
  • Patients who are eligible can book online here
  • Other members of the public cannot book appointments to get the COVID-19 vaccine at this time

COVID-19 Vaccine After-Care Sheet (Centre for Effective Practice)

February 24, 2021

From Hamilton Public Health Services

Subject: Community healthcare workers can now register for COVID-19 vaccination in Hamilton

All community healthcare workers (see list below) who live and/or work in Hamilton are can now register for COVID-19 vaccination. Once registered, individuals will be called for a COVID-19 vaccination appointment, the appointments bookings are not allocated in order of registration, but rather are based on prioritization outline in the Province of Ontario’s COVID-19: Guidance for Prioritizing Health Care Workers for COVID-19 Vaccination. Healthcare workers will be contacted for an appointment in upcoming weeks or months as individuals become eligible.  We appreciate your patience during this process.

Hospital workers should not register through this site but continue to use the process outlined by their employer.

Online registration is now available by visiting Registration is a necessary first step prior to booking an appointment.

Once registered, the healthcare worker will be contacted to by phone to book their appointment and confirm the clinic location. Healthcare workers will be contacted for an appointment in upcoming weeks or months as individuals become eligible. Vaccine appointments will begin on Friday, February 26 at Hamilton Health Science’s fixed-site vaccination clinic. Please note, that community healthcare workers will be asked for proof of employment when arriving to receive their vaccination. If this this is not provided, they will not receive their vaccine.  A list of accepted “proof of employment” examples will be included in the verification email at booking.

Registration is not currently available to the public. Information on registration for other populations will be available as we receive more information from the Province.

We are asking for your help to pass this message along today to your networks that have community healthcare workers.  

For more information about the COVID-19 vaccine:

Who is eligible?

All health care workers are eligible. Staff working within a health care organization (e.g. physician’s office, clinic) are also eligible to register for vaccine. For the purposes of this vaccine prioritization, ‘health care worker’ is defined as: 

  • Anyone working or volunteering in a health care organization (includes regulated health professionals as well as staff not providing direct patient care such as cleaning, food or administration services) 
  • Any worker providing healthcare services or direct patient service in a setting outside of a health care organization

Source: COVID-19: Guidance for Prioritizing Health Care Workers for COVID-19 Vaccination

Health care workers in the following settings who live or work in Hamilton are eligible to register for COVID-19 vaccination:

  • Adult day programs for seniors
  • Assisted living
  • Birth Centre
  • Campus health / Student health centre
  • Community based specialist
  • Community diagnostic imaging
  • Community Health Centre
  • Correctional facilities
  • COVID-19 Isolation Centre
  • COVID-19 laboratory services
  • COVID-19 Testing locations: Assessment Centre, mobile testing team, community testing location
  • COVID-19 vaccination clinic
  • Daycare/School health care worker
  • Death investigation professionals
  • Dental office
  • Developmental Services
  • Dietary/Nutrition
  • Gynecology/obstetrics
  • Hamilton Fire Department
  • Hamilton Paramedic Services
  • Home and community care
  • Hospice and palliative care
  • Independent health facilities (e.g. Optometry, Opticianry, Podiatry, Audiology, medical and surgical specialists)
  • Indigenous Community Health Centre
  • Mental health and additions services
  • Midwifery
  • Naturopathy/Holistic Care
  • Needle exchange/syringe programs
  • Non-acute rehabilitation and therapy clinics, including chiropractic, chronic pain, kinesiology, occupational therapy, physiotherapy, psychiatry, psychology, psychotherapy, registered massage therapy, acupuncture, other therapy)
  • Nurse-Practitioner-led clinics
  • Nursing agencies – contract
  • Other health care services for Indigenous populations
  • Other laboratory services
  • Otolaryngology (ENT)
  • Pharmacy
  • Primary care clinics — such as physician’s offices, walk-in clinics
  • Public health
  • Residential facilities
  • Respirology (Respiratory Therapy)
  • Sexual health clinics
  • Shelters
  • Social Work
  • Supervised consumption sites
  • Supportive housing

Injection Technique and SIRVA (Bancsi, Houle and Grindrod, Canadian Family Physician)