COVID-19, vaccination and special populations

Human Respiratory System Lungs Anatomy

For those with chronic health conditions, those who are pregnant and immunocompromised patients, the COVID-19 pandemic and the availability of effective vaccines has posed many questions.

The good news is that in the overwhelming number of cases, COVID-19 vaccines approved for use in Canada are both safe and effective. This is especially reassuring for the long list of those with underlying chronic health conditions who are more likely to get severely ill from SARS-COV2 infection.

Chronic conditions

The Centers for Disease Control and Prevention in the US has published a list of these conditions which includes:

  • Cancer (other than superficial skin cancers)
  • Chronic kidney disease
  • Chronic lung disease
  • Dementia
  • Diabetes
  • Heart conditions
  • Transplant patients

Several Canadian medical organizations have published warnings about the increased risk of severe illness from COVID-19 specific to their populations. For example in a guideline published in April, 2020 that remains current, the Canadian Thoracic Society (CTS) stated that longitudinal experience with influenza and initial experience with COVID-19 “suggests that patients with chronic lung disease are at risk for severe complications of SARS-CoV2 infection.”

In April 2021, the CTS produced recommendations on COVID-19 vaccination and noted that for those with chronic medical conditions “no matter which COVID-19 vaccine becomes available to you first, you can feel confident in its ability to protect you, as long as you continue being cautious until positive cases, hospitalizations, and deaths are significantly reduced nationwide.”

COVID-19 vaccines available in Canada have shown their value across a broad spectrum of other populations with pre-existing conditions or special circumstances. The only segment of the population for which currently approved COVID-19 vaccines are contraindicated are those with a history of anaphylaxis after previous administration of thesame vaccine. Vaccines are also contraindicated for those with proven immediate or anaphylactic hypersensitivity to any component of the vaccine or its packaging.

However the CTS and other organizations have also stressed that “vaccines aren’t a silver bullet, especially as the pandemic is ongoing. They must be combined with other public health measures to decrease risk of virus transmission including: frequent hand washing or use of alcohol-based hand sanitizers, wearing face masks, and physical distancing should continue to be observed as per local recommendations.”


When COVID-19 vaccines became available one of the first discussions involved pregnant individuals and whether they could safely be vaccinated.

The Society of Obstetricians and Gynecologists of Canada (SOGC) issued guidelines on the use of COVID-19 vaccines in pregnant women in December, 2020 and reaffirmed them in May, 2021. These guidelines state that “all available COVID-19 vaccines approved in Canada can be used during pregnancy and breastfeeding”, and that pregnant individuals should be offered vaccination at any time during pregnancy or breastfeeding if no contraindications exist.

The SOGC added “the decision to be vaccinated is based on the individual’s personal values, as well as an understanding that the risk of infection and/or morbidity from COVID-19 outweighs the theorized and undescribed risk of being vaccinated during pregnancy or while breastfeeding.” The society cited evidence showing that “compared to non-pregnant women with COVID-19, pregnant women are at increased risk of admission to hospital, critical care and invasive ventilation compared to age-matched peers.”

Noting that pregnant and breastfeeding individuals were excluded from the available Phase II and Phase III studies for the Pfizer-BioNTech and Moderna COVID-19 vaccines, the SOGC said no greater adverse effects were seen in those women who were pregnant and had received the vaccine. The guideline added that “because mRNA vaccines are not considered live virus vaccines, they are not hypothesized to be a risk to the breastfeeding infant.”

Similarly, pregnant and breastfeeding individuals were excluded from the Phase III AstraZeneca Trials, and in the inadvertent pregnancies that were reported there had been no adverse events to date. Preclinical trials with AstraZeneca vaccine did not demonstrate adverse effects on fertility, pregnancy, fetal or postnatal outcomes.

Immunocompromised patients

Immunocompromised patients are at higher risk of more severe symptoms from SARS-CoV2 than the general population. In the early stages of the pandemic and then with the availability of effective vaccines, questions were raised about whether systemic therapies might increase the risk from COVID-19 and/or lessen the effectiveness of COVID-19 vaccines.

Most organizations now feel continuing to use such therapies in this population outweighs any potential risks.

As the Canadian Digestive Health Foundation bluntly states in their advice about COVID-19 on their website: “First and foremost, if you are on a medication that suppresses your immune system, DO NOT STOP TAKING YOUR MEDICATION  (emphasis theirs)We know that with everything going on, this might be your first reaction, but this is absolutely not an option. Stopping any sort of treatment plan without direct guidance from your healthcare provider is dangerous and could land you in the hospital, which is the absolute last place you want to be right now. Please, continue to take your medication and implement extra precautions in your day to day life until the threat has passed.”

The <Canadian Dermatology Association (CDA) policy statement on patients taking systemic therapies published in January, 2021 says “all patients, regardless of ongoing treatment, should receive vaccination unless they have documented, severe allergic reactions to one or more vaccine constituents.” The association does note that while “modest attenuation” of vaccine effectiveness may be expected due to use of some drugs, “only when maximization of vaccine effectiveness is of paramount concern should interruption of systemic therapy be considered.” In addition, the CDA states “there are no additional safety concerns associated with vaccinating patients on systemic therapies.”

In May the Canadian Rheumatology Association (CRA) published a statement recommending any patients who have an autoimmune rheumatic disease, or are immunosuppressed due to treatment, should receive any of the vaccines approved in Canada. The CRA added that “as recommendations change frequently, decisions on which vaccine is appropriate should be based on the most current public health recommendations. Patients should also be counseled about the unknown vaccine safety profile in these populations, in addition to the unknown effectiveness and the potential for lower vaccine response in those who are immunosuppressed.”

In its statement in early July, the National Advisory Committee on Immunization (NACI) states that body “preferentially recommends that a complete vaccine series with an mRNA COVID-19 vaccine should be offered to individuals in the authorized age group with an autoimmune condition,” and that the AstraZeneca vaccine may be used if mRNA vaccines are inaccessible.

In support of this statement, NACI notes “observational studies in individuals with autoimmune conditions indicates that the frequency and severity of adverse events in this population is comparable to that of individuals without autoimmune conditions and what was reported in clinical trials.” As for the impact of immunosuppressive therapies, NACI says observational studies have shown showed diminished or delayed immune responses to the mRNA or AstraZeneca vaccines but that these data are difficult to interpret because of the limited number of participants and the lack of an immunological correlate of protection against SARS-CoV-2 infection.

The Canadian Thoracic Society and the Canadian Society of Allergy and Clinical Immunology state that when it comes to approved COVID vaccines “there is no evidence of safety or efficacy concerns for patient with asthma on biologic therapy.” However they add “The COVID-19 vaccine should not be administered on the same day as a biologic for asthma where possible. Patients with asthma should ideally receive a COVID vaccine 72 hours apart from their regular biologic, to make it easier to tell what injection may have caused a problem if the patient has a reaction.”


Dr. Jean Bourbeau is director of the COPD Clinic and the Pulmonary Rehabilitation Unit at the MUHC Montreal Chest Institute and a past president of the Canadian Thoracic Society. Dr. Alan Kaplan is a family physician in York Region, ON and chair of the Family Physician Airway Group of Canada.
Profil picture of Dr. Jean Bourbeau

About the author

Jean Bourbeau is the Director of the Research Institute MUHC’s Center for Innovative Medicine, the COPD Clinic and the Pulmonary Rehabilitation Unit at the MUHC Montreal Chest Institute. He has been President of the Canadian Thoracic Society. His work and research on COPD, pulmonary rehabilitation, integrated self-management programs for patients with COPD (‘Living Well with COPD’) have had an impact not only in the field of research, but also in clinical practice at the national and international level.

Dr. Jean Bourbeau