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 latest information about COVID-19 vaccines in Hamilton, including how to book an appointment, can be found on the City of Hamilton website.

FAQ: Working at the Hamilton COVID-19 Vaccine Clinics

Bivalent boosters are recommended over monovalent boosters.

Recommendations for booster doses, intervals, bivalent brands approved for different ages and timing after COVID infection can be found here in the Ministry of Health COVID-19 Vaccine Guidance (The table of contents has “jump links” to sections).

There are VERY FEW, IF ANY justifications for exemption. Dr. Kati Ivanyi has kindly provided the detailed information below:

There are likely to be very few medical exemptions to COVID-19 vaccination. The largest group of individuals who receive a medical exception will be those with severe allergic reactions or anaphylaxis to a previous dose of a COVID-19 vaccine or to any of its components and who have been assessed by an allergist/ immunologist to review methods for possible (re)administration of a COVID-19 vaccine. There are existing protocols to administer COVID-19 vaccines to individuals with other types of allergies. These other types of allergies do not on their own constitute the grounds for a medical exemption. 

  • Individuals who have had an allergic reaction within 4 hours and/or anaphylaxis that occurred with a vaccine or injectable medication that does not contain a Version 1.0 (August 18, 2021) MINISTRY OF HEALTH Page 6 of 21 component or cross-reacting component of the COVID-19 vaccines can receive the COVID-19 vaccine followed by observation for a minimum of 30 minutes. 
  • Individuals with a history of significant allergic reactions and/or anaphylaxis to any food, drug, venom, latex or other allergens not related to the COVID-19 vaccine can receive the COVID-19 vaccine followed by observation for a minimum of 15 minutes. Individuals with allergy issues like allergic rhinitis, asthma and eczema can receive the vaccine followed by observation for a minimum of 15 minutes 

Another group of individuals who may receive a medical exemption are those who are delaying their second dose because of a diagnosed episode of myocarditis/pericarditis after receipt of an initial dose of an mRNA vaccine. 

In some instances, the medical reason for the person not being vaccinated may be time-limited (e.g., timing around a procedure or other medical treatment). The Directive requires that the note from the physician/nurse practitioner specifies whether the reason is permanent or time-limited. If time-limited, the note should indicate how long it is expected to last. Covered Organizations should communicate this requirement to anyone who is planning on submitting proof of a medical reason. 

Proof must be provided by either a physician or a nurse practitioner (note: A nurse practitioner is a registered nurse who holds an extended certificate of registration under the Nursing Act, 1991). 

Referral and consultation support for Physicians and Nurse Practitioners is available through Ontario’s eConsult Service and OTN Hub. 

More information about Medical Exemptions can be found in the Vaccine Information Sheets and Special Populations Documents available on the ministry’s website.

Here is a statement from CPSO on exemptions.

Here is a Sample Statement of Medical Exemption form.

Here is a resource about COVID-19 Vaccine Medical Exemptions (Focused Communications, September 26, 2021).

This directive provides guidance and specifies the requirements for various workplace settings providing care.
Resource Guide for Directive 6.

1. From Lifelabs:

The following limitations of COVID-19 antibody testing should be considered:

  • Positive antibody (serology) test results do not infer immunity and protection from re-infection
  • Serology results should not be used to exclude active infection
  • Antibody testing performed < 3 weeks after onset of symptoms has reduced clinical sensitivity and may lead to false negative results
  • Rare false positive results may be due to cross-reactivity with other coronaviruses
  • Immunosuppressed individuals or those with mild disease may not produce measurable antibody levels
  • Some studies indicate that a small percentage of people infected with SARS-CoV-2 (<4%) do not have detectable antibodies.
  • The COVID-19 antibody test currently offered by LifeLabs cannot detect antibodies generated after vaccination.

2. From MOHLTC: Case Definitions and Disease Specific Information

Laboratory-based serology testing: detects antibodies to SARS-CoV-2

Purpose: Serology testing is available for clinical use under specific clinical indications:

  • Patients presenting with symptoms compatible with Multisystem Inflammatory Syndrome in Children (MIS-C) or Adults (MIS-A) who do not have laboratory confirmation of COVID-19 by molecular testing.
  • Testing may be considered for patients with severe illness who have tested negative for COVID-19 by molecular testing and where serology testing would help inform clinical management and/or public health action. Serology testing for these patients requires consultation and approval by the testing laboratory.

Serology should NOT be used for screening and diagnosis of acute COVID-19 infection, determining immune status, vaccination status.

3. From Public Health Ontario 

Coronavirus Disease 2019 (COVID-19) – Serology

COVID-19 serology should not be used as a diagnostic test, except in very rare circumstances, due to the potential for false negative and false positive results. SARS-CoV-2 antibodies do not correlate with recovery or infectivity. Serology also cannot be used to assess whether a person is immune to COVID-19 or to determine their COVID-19 vaccination status.

Testing Indications

This test is intended for use as an aid in determining if a patient with an adaptive immune response has been previously exposed to SARS-CoV-2. Currently, it is not known whether the presence of SARS-CoV-2 IgG antibodies correlates with immunity. It can take at least 7-14 days from symptom onset to develop a measurable SARS-CoV-2 IgG response with some individuals never seroconverting. In evaluations at PHO, the highest sensitivity of the assay was seen at >14-21 days from symptom onset. Further, the duration of the IgG response is variable, with a reduction in IgG levels and seronegativity in as little as 2-3 months in some patients.  Additional information about COVID-19 serology testing can be found here: What We Know So Far – COVID-19 and Serology Testing.  

In patients with a low pretest probability (e.g. no high-risk exposure or symptoms compatible with COVID-19), there is a risk that a positive COVID-19 serology result is a false positive, even with high test specificity. Conversely, there is an increased risk of a false negative result if serum is taken too early (i.e., <2-3 weeks after symptom onset) or too late (i.e. antibody waning), from a patient with a mild infection, or if the patient is immunocompromised. Given these caveats and significant gaps in our understanding of the immune response in COVID-19, serology testing has very limited clinical value for individual patients. Detection of viral RNA by molecular testing, such as PCR, is the gold standard for diagnosing COVID-19 in suspected patients. If the patient is symptomatic, a respiratory specimen should be tested by COVID-19 PCR Testing. 

Currently, the limited clinical value for individual patient testing precludes the widespread use of COVID-19 serology as a clinical diagnostic tool. It may be considered for clinical use as an adjunct to COVID-19 PCR testing in:

  • Patients suspected to have multisystem inflammatory syndrome in children (MIS-C) or adults (MIS-A) with a negative, indeterminate, or inconclusive PCR test result or who were not tested

Other clinical scenarios of severe illness with negative PCR tests, where serology results may be helpful for clinical management and/or public health action, will be considered following consultation and approval by a PHO Microbiologist before specimen collection. 

Specimens submitted for testing for indications other than MIS-C/MIS-A or without prior approval will be rejected.

Serology should NOT be used for:

  • The diagnosis of acute infection, reinfection, or determining the infectivity of the patient
  • Determining immune status of the patient (i.e. protection against future infection)
  • Determining COVID-19 vaccination status of the patient or serological response to vaccination


SARS-CoV-2 IgG testing should NOT be used to determine a patient’s immune status, vaccination status, or infectivity. Results should be interpreted in the context of clinical and exposure history.

A negative SARS-CoV-2 IgG test result:

  • Does not rule out current or previous SARS-CoV-2 infection
  • If clinical suspicion is high, consider retesting in 2-3 weeks
  • Negative results may occur if the specimen is collected too soon or too late following infection, if the patient is immunocompromised, or if the patient is too young to produce an effective adaptive immune response (eg. neonate)

A positive COVID-19 IgG test result:

  • Indicates recent or prior infection with SARS-CoV-2 virus
  • An individual with evidence of seroconversion over a 4-week interval, regardless of nucleic acid amplification testing (e.g. real-time PCR), is considered a “confirmed” case if the individual has not received a COVID-19 vaccination
  • An individual with antibody detected in a single serum specimen is considered a “probable” case if they have not yet received a COVID-19 vaccination AND had symptoms of COVID-19 AND had a high-risk exposure or epidemiological link AND antibody was detected within four weeks of symptom onset1
  • False-positive results may occur from cross-reaction due to prior infection with other human coronaviruses, including SARS-CoV-1 and certain seasonal coronaviruses (e.g. human coronavirus OC43) 

If the patient is symptomatic, a respiratory specimen should be collected and tested for SARS-CoV-2 using a molecular assay.

There is currently no data available to determine if these commercial assays can or cannot detect IgG antibodies produced in response to infection by SARS-CoV-2 variants of concern (VOCs).  

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.

Comparative brand information can be found on the Centre for Effective Practice website.

PrOTCT Framework for the COVID-19 vaccine discussion (Centre for Effective Practice)

FAQ COVID mRNA Vaccines for Children (Focused Communication, November 8, 2021)

Public Health Services Quick Reference Tool for Staff

Health Care Provider Toolkit

Health Care Provider Toolkit: COVID-19 Vaccines for Ages 5-11

Translated Vaccine Fact Sheets (Ages 5-11) (City of Hamilton) (French, Spanish, Arabic, Simplified Chinese)

I am pregnant or breastfeeding. Should I get the COVID-19 vaccine? (Provincial Council for Maternal and Child Health, January 25, 2022)

More information on vaccines in children can be found in Section 11: Guidance on Vaccines and Special Populations / Children and adolescents age 18-24

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

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.

Current Information about Dose Interval

Primary series and booster intervals vary depending on age and immune status and can be found in the section in Ministry of Health COVID-19 Vaccine Guidance (the table of contents has “jump links” to section)

Timing Dosing FAQs

Q. How long should a patient wait after and before another vaccine before getting the COVID-19 vaccine? On September 28, NACI updated the recommendation on the timing of COVID-19 and non COVID-19 vaccines administration. NACI now recommends that COVID-19 vaccines may be given at the same time as, or any time before or after, other vaccines, including live, non-live, adjuvanted or unadjuvanted vaccines.

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 until they have recovered. It is recommended that people who have had a COVID infection wait for a period for time before getting their first or next vaccination. Recommended intervals vary according to whether the vaccine is part of the primary or a booster, and the patients immune status, and can be found in the Ministry of Health COVID-19 Vaccine Guidance (the table of contents has “jump links” to section).

Q. Should a patient who had COVID-19 previously still receive the full course? 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.

For additional information on immunodeficiency conditions, consult the COVID-19 resources on the Canadian Society of Allergy and Clinical Immunology webpage.

Recommendation: Since all Health Canada authorized COVID-19 vaccines are not live vaccines, they are considered safe in these groups, however there is limited data on efficacy. Individuals who were immunocompromised due to disease or treatment were excluded from some of the Phase III trials for COVID-19 vaccines available at present and those with autoimmune conditions had very small representation.

A. Individuals in the authorized age group with autoimmune conditions, immunodeficiency conditions or those immunosuppressed due to disease or treatment including 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 etc.) should be offered the vaccine. These individuals are strongly encouraged to speak with their treating health care provider regarding the timing of vaccination in relation to therapy for their underlying health condition and/or treatment modification in view of possible decreased vaccine effectiveness with the use of immunosuppressive therapy.

B. All other individuals in the authorized age group with autoimmune conditions, immunodeficiency conditions or those immunosuppressed due to disease or treatment may choose to receive the vaccine. These individuals may choose to consult with their health care provider prior to vaccination (for example, to discuss immunosuppressive medication management/timing in relation to their vaccination).

For frequently asked questions about COVID-19 vaccine and adult cancer patients, consult Cancer Care Ontario.

Public Health Measures

Getting a full series of a COVID-19 vaccine is an important step in protecting this population from COVID-19. The effectiveness of the COVID-19 vaccines is not yet well understood in those who are immunocompromised and continues to be studied. No vaccine is 100% effective, and reduced effectiveness has been noted for variants. Measures can be taken to enhance protection against COVID-19 for those who are immunocompromised:

  • It is recommended that all people with whom the individual regularly comes into close contact (e.g. family, friends) complete a full vaccine series (i.e. “ring vaccination”).
  • It is recommended to consider the risks of catching COVID-19 or passing it on to others when meeting with those outside the individual’s household. Strategies to reduce the risk include:
    • Meeting outside if possible
    • When meeting inside, ensure the space is well ventilated, for example by opening up windows, doors, or other actions to increase fresh air
    • Limiting the size of the gathering and considering the vaccination status of others that will attend.
  • It is recommended that immunocompromised individuals follow Public Health measures that have been shown to reduce the risk of COVID-19 transmission, even after immunization. These recommendations may continue for immunocompromised individuals even after they have been lifted for the general population. This includes mask wearing and physical distancing. A well fitting, well-constructed non-medical mask that includes a filter layer is recommended, or a medical mask if one is available.
  • Individuals are encouraged to speak with their health care provider as needed to assess the risks in their clinical context.

The latest recommendations on vaccination during pregnancy and breastfeeding plus decision making resources can be found in the Ministry of Health COVID-19 Vaccine Guidance document. Note there is a longer recommended interval after COVID infection for vaccination in pregnancy.

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).

For frequently asked questions about COVID-19 vaccine and adult cancer patients, consult Cancer Care Ontario.

Primary series and booster intervals and authorized brands vary depending on age and immune status  and can be found in the table in the Ministry of Health COVID-19 Vaccine Guidance document.

Information for patients on vaccines in children aged 5-11

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.

For additional information on organ transplantation, consult the Canadian Society of Transplantation statement on COVID-19 vaccination.

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.

The Crohn’s and Colitis Canada COVID-19 and IBD Task Force recommends all of these COVID-19 vaccines be administered to patients with IBD at the earliest available opportunity. This one-page IBD info sheet summarizes key points for patients and healthcare providers.

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.

Reports of vaccine-induced prothrombotic immune thrombocytopenia VIPIT), specific to AZ vaccination, prompted NACI’s March 29, 2021 recommendation to suspend AZ vaccine use in people age 55 and younger. This Science Brief on VIPIT from the COVID-19 Science Advisory Table lists the symptoms for which to monitor following vaccination.

In the U.S., where the AZ vaccine is not in use, the medical advisory board of the Platelet Disorder Support Association (PDSA) has stated (Feb.12, 2021) that for people without pre-existing thrombocytopenia/ITP, “the benefit to risk ratio strongly favors vaccination over avoiding vaccination for fear of thrombocytopenia of all eligible adults,” even for those perceived to be at low risk of serious illness from COVID-19. It says the relationship between the cases of severe thrombocytopenia and the vaccine, if any, is uncertain. For patients with pre-existing ITP, PDSA says “it would seem prudent” to consult with a hematologist re platelet counts, and that these patients “should not hesitate to be vaccinated based on all available information but individual patients may choose to consult with their hematologist or another physician before proceeding.”

Thrombosis Canada (TC) states that “people who have COVID-19 are at much higher risk of developing blood clots” than for VIPIT from vaccination and “strongly recommends that people receive vaccinations for COVID-19, including the vaccine made by AstraZeneca.” TC reaffirmed its position to “strongly recommend that all eligible adults receive the AstraZeneca and Johnson & Johnson (Janssen) vaccine, including people with a prior blood clot, those with a blood clotting tendency (e.g., factor V Leiden mutation), and people who are receiving blood thinners as the benefits of receiving the vaccine far outweigh the risks.”

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 overall rate is reported as low, events appear higher in males vs. females, tend to happen within a few days of vaccination and most cases were mild and could be treated conservatively.

CDC data report 12.6 cases per million for second doses of any mRNA vaccine in the 21 days following vaccination per CDC data. A more recent study from Israel among 2.5 million patients who had received at least one dose of the Pfizer mRNA vaccine, the estimated incidence of myocarditis was 2.13 cases per 100,000 persons; the highest incidence was among male patients between the ages of 16 and 29 years (10.68%). Most cases of myocarditis were mild or moderate in severity, and one patient died (patient had a pre-existing cardiac conditions and died of unknown cause after hospital discharge).

Here are several useful documents on myocarditis and COVID-19 vaccines.

This graphic from Unambiguous Science and Science Whiz Liz summarizes the evidence so far.

From NACI (Summary of NACI Updates July 2, 2021):

  • A small number of cases of myocarditis and/or pericarditis following immunization with mRNA COVID-19 vaccines have been reported in Canada and internationally. Internationally, cases have been reported more frequently in adolescents and younger adults under 30 years of age, more often in males than in females, and more frequently after a second dose. The majority of cases have been mild and individuals have recovered quickly.
  • NACI continues to strongly recommend that a complete series with an mRNA vaccine should be offered to all eligible individuals, including those 12 years of age and older. mRNA COVID-19 vaccines provide very good protection against SARS-CoV-2 infection and symptomatic COVID-19 disease, including severe illness, hospitalization and death.
  • People who are offered an mRNA COVID-19 vaccine should be informed of the very rare risk of myocarditis and/or pericarditis following immunization and should be advised to seek immediate medical attention if they develop symptoms, which may include chest pain, shortness of breath, or the feeling of a fast, pounding or fluttering heartbeat. Cases typically occur within a week after the receipt of an mRNA vaccine dose, more commonly after a second dose. Any potential cases should be investigated with medical assessment regardless of timing from vaccination to onset.
  • As a precaution, NACI recommends that individuals who experienced myocarditis and/or pericarditis after a first dose of an mRNA COVID-19 vaccine should wait to receive a second dose until more information is available.

Reports of myocarditis/pericarditis after COVID-19 vaccination: FAQ for health-care providers (SickKids, June 16, 2021)

COVID-19 Vaccine Information Sheet: For Youth (age 12-17) (Ontario Ministry of Health, December 14, 2021)

Vaccine-induced Thrombotic Thrombocytopenia (VITT)

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?

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

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