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People who are at a higher risk of severe COVID-19 include individuals with poor immune function due to underlying medical conditions or due to immune-suppressant medications. In these populations, risk mitigation measures against COVID-19 are particularly important. This includes non-pharmaceutical interventions such as masking and distancing to prevent infection, as well as following recommended vaccination schedules.

The CITF has funded multiple studies looking at vaccine safety and effectiveness in these populations, including those with HIV, immune-mediated inflammatory diseases such as inflammatory bowel disease and inflammatory arthritis, chronic kidney disease, recipients of solid organ transplants, and people living with or being treated for cancer.

In this synthesis on the state of research on people whose health conditions put them at higher risk of severe COVID-19, we present findings from CITF-funded research to inform protection in this population.

The key takeaways:

  • Vaccines have worked well at generating immune responses and warding off severe disease and death in various immunocompromised populations, though in many cases three doses (not two) should be considered the primary regimen.
  • COVID-19 vaccines have proven to be safe for immunocompromised people.
  • Keeping up to date with the recommended vaccine booster schedule (i.e. a dose every four to six months) is important to sustain adequate levels of protection.
  • Vaccines based on the original virus strain have been less effective in protecting against Omicron compared to earlier variants. The new bivalent vaccines recently approved in Canada may offer greater protection, however it is too early to say for certain for these populations.
  • Because of their vulnerability to infection, it is recommended that immunocompromised people continue to be cautious, wearing masks, physical distancing, and avoiding crowded settings.

The latest findings in people living with HIV (PLWH)

There are nearly 63,000 people living with HIV in Canada (1). The COVID-19 pandemic has substantially affected the lives of PLWH, who frequently face multiple comorbidities and may be at heightened risk for COVID-19 complications, while contending with spillover effects, such as equitable access to treatment and prevention (2).

  1. The initial two-dose COVID-19 vaccine regimen has been effective at inducing immunity in PLWH
    • Results from CITF-funded studies led by Drs. Zabrina Brumme, Mark Brockman, Marc Romney, and Aslam Anis highlight that, three months after a second vaccine dose, HIV infection had no negative effect on COVID-19 vaccine-acquired serological and cellular immunological responses (3). Antibody responses against the receptor-binding domain (RBD) of the spike (S) protein were of similar magnitude and durability in PLWH compared to people without HIV (4).
    • A longer interval between the first and second vaccine dose was associated with higher antibody concentrations immediately after the second dose, both in PLWH and people without HIV, but this impact diminished over time (4).
    • Weaker antibody responses after two doses were generally associated with those who had a higher number of chronic conditions, older age, and immunization with two doses of the AstraZeneca vaccine, regardless of HIV status (4).
    • In an analysis of health administrative data in Ontario led by Dr. Ann Burchell, two doses of COVID-19 mRNA vaccine offered substantial protection against symptomatic illness and hospitalization/death in PLWH prior to the emergence of the Omicron variant. COVID-19 mRNA vaccine effectiveness (VE) does not seem to be lower among PLWH in populations that, for the most part, have regular medical care and/or are taking antiretroviral medication (5). Similarly, as the lead of BC component of this study, Dr. H. Samji and collaborators found similar effectiveness of the vaccine in the comparable PWLH BC population.
    • In a CITF-funded multi-center longitudinal observational cohort of PLWH, Drs. Cecilia Costiniuk, Curtis Cooper, and Aslam Anis found that anti-RBD levels were similar between PLWH and HIV-negative controls at three and six months post second dose. Anti-S IgG levels were also similar at three months after the second dose. However, a lower proportion of PLWH than controls maintained vaccine-induced anti-S IgG immunity six months after the second dose. That said, vaccine-induced IgG was elicited in the vast majority of PLWH, in a similar proportion to those in the control group (manuscript accepted) (6).
    • In multivariable analyses, neither age, immune non-response, multimorbidity, sex, vaccine type or timing between doses were associated with reduced IgG response (manuscript accepted).
  1. Booster doses further strengthen vaccine-induced immunity
    • According to Dr. Mario Ostrowski’s CITF-funded study, serum IgG levels for spike and RBD increased after each vaccine dose (D1<D2<D3). The differences in anti-S and anti-RBD neutralization titers in PLWH were significantly lower than they were in people without HIV after two doses, but attained a level similar to the general population after the third dose.
    • Ostrowski also pointed out that PLWH over the age of 50 had a defective ability to neutralize SARS-CoV-2 after two doses of vaccine, but their neutralizing capacity improved following a booster dose.
    • A third dose of Moderna vaccine induced a more robust antibody response than a third dose of Pfizer vaccine. Prior SARS-CoV-2 infection also increased virus neutralizing antibodies (4).
    • In the study from Drs. Costiniuk, Cooper, and Anis, the proportions of participants achieving comparable anti-RBD and anti-S IgG levels were similar between PLWH and HIV-negative controls at one month post third dose. Given that a slightly lower proportion of PLWH maintained vaccine-induced anti-S IgG immunity six months post second dose, these findings also demonstrate the importance of timely boosting in this population (manuscript accepted).
  1. Other considerations – vaccines remain less efficient against the Omicron strain
    • A third dose boosted antibody responses in PLWH above that which was seen after the second dose (4).
    • Males had a slightly lower antibody response following a third dose of vaccine than females (4).
    • Neutralizing activity against Omicron remained four- to eight-fold lower than against the original (wild-type) SARS-CoV-2 strain in PLWH after both two and three vaccine doses (4).

These results highlight the importance of being up to date with vaccinations and incorporating the bivalent boosters recently approved by Canada’s National Advisory Committee on Immunization (NACI).

The latest findings in people with immune-mediated inflammatory diseases (IMIDs)

More than 7 million Canadians live with immune-mediated inflammatory diseases (IMID). CITF-funded research has studied groups of individuals with rheumatoid arthritis (RA) RA is an autoimmune disease where the immune system attacks healthy cells in your body by mistake, causing inflammation in the joints., ankylosing spondylitis (AS) AS is a type of arthritis that affects the spine., psoriasis An inflammatory skin condition that can also cause arthritis., and inflammatory bowel disease (IBD) Inflammatory bowel disease (IBD) is a term used to describe disorders that cause inflammation of tissues in the gastrointestinal tract. The two most common forms of IBD are Crohn’s disease and ulcerative colitis. . Individuals living with these conditions are often on immunosuppressant therapies, which may reduce their immune system’s response and make them more susceptible to severe SARS-CoV-2 infection (7).

According to the CITF-funded SUCCEED study (Safety and immUnogenicity of Covid-19 vaCcines in systEmic immunE mediated inflammatory Diseases, a national team led by Dr. Sasha Bernatsky, SARS-CoV-2 infections were more likely to occur among people with IMID who were young (i.e. under 50 years old) and resided in lower-income neighborhoods (8).

The following results may apply to those diagnosed with a variety of IMIDs; specifics regarding IBD will be discussed below in a separate section.

  1. Vaccine uptake is high among individuals with IMIDs
    • The total cumulative percentage of individuals in Ontario who received two doses of COVID-19 vaccine was higher in people with IMID (ranging from 83.8-88.2%) than in the general population (77.9%) (8, 9)
    • The cumulative percentage of Canadians who did not come back for a second vaccine dose was also lower among people with IMIDs (between 1.6 and 1.9%) than in the general population (2.4%) (9).
  1. Two doses of vaccines have been proven effective in people with IMIDs, but booster doses are required
    • A SUCCEED study analysis led by Dr. Jessica Widdifield estimated that vaccine effectiveness against hospitalization and/or death after two doses of mRNA vaccine was 92%-97% in people with IMIDs (8).
    • Vinod Chandran, Anne-Claude Gingras and Tania Watts, through their CITF-funded IMPACT study (Immune response after COVID-19 vaccination during maintenance therapy in immune-mediated inflammatory diseases: an observational cohort study), found that two to four weeks following the second dose of vaccine, 100% and 99.2% of individuals with IMIDs seroconverted (i.e., developed antibodies) for both anti-S and anti-RBD IgG, respectively. They also observed an increase in T-cells active against SARS-CoV-2 following the second vaccine dose (10).
    • In the pre-Omicron era, vaccine effectiveness against infection seven days after receiving a third dose ranged from 76% to 96%. (8).
  1. Third vaccine dose provided a promising immune response against Omicron infection

The IMPACT study demonstrated that:

  • Following a third dose of Pfizer or Moderna monovalent vaccine during the Omicron era, 92% of people with IMIDs who had not been infected by SARS-CoV-2 showed greater anti-S and anti-RBD antibody levels than convalescent individuals (those recovering from a SARS-CoV-2 infection) (7).
  • T-cell responses increased after the third dose when compared to the second mRNA vaccine dose. There were no observed differences in T cell responses (specifically IL-2 and IL-4 levels) against the Omicron variant compared to the wild type (7).
  • Analyses underway led by SUCCEED investigator Dr. Dawn Bowdish also highlighted that three doses of mRNA vaccine elicited more robust and durable humoral and cellular immune responses against all SARS-CoV-2 variants, including Omicron.
  1. Effectiveness of vaccination depends on the immunomodulatory treatment

Several treatments are available to people with IMIDs. IMPACT participants received biologics and/or anti-metabolite therapies to manage their underlying condition.

  • Antibody levels and neutralization efficacy against variants of concern, including Omicron, were substantially lower in those with IMIDs who were receiving anti-TNF treatments Anti-TNF therapies suppress the immune system by blocking the activity of TNF, a substance in the body that can cause inflammation and lead to immune-system diseases, such as rheumatoid arthritis, ankylosing spondylitis etc. , compared to healthy controls. They were also undetectable against Omicron three months after the second vaccine dose (10).
  • IMPACT IMID participants on anti-TNF drugs also had lower cellular immune responses after the second vaccine dose, versus those not on these drugs.
  • Persons on anti-TNF therapy mounted lower humoral and cellular responses, even after the third vaccine dose (not yet published data from the SUCCEED and IMPACT studies).
  1. The original monovalent Moderna vaccine appears to induce a stronger immune response than the monovalent Pfizer vaccine
    • Vaccine effectiveness against infection after one and two doses of vaccine was higher for those who received the Moderna monovalent vaccine compared to those who received the Pfizer monovalent vaccine (8).
    • Again, only comparing the monovalent formulations, two doses of Moderna, or mixed dosing of Moderna and Pfizer vaccines, elicited a more robust antibody response than two doses of Pfizer vaccine alone (10).


Several members of the  SUCCEED research team (including Drs. Glen Hazelwood, Ines Colmegna, Carol Hitchon, Paul Fortin, Sasha Bernatsky, and Dawn Richards) contributed to the Canadian Rheumatology Association (CRA) guidelines for people with rheumatic diseases. These guidelines indicate that:

  • Three doses of COVID-19 vaccine is a primary regimen for those on certain immunosuppressive medications. In addition to the primary series, it is recommended that all those over the age of 18 receive an additional booster dose at least three to six months after their last vaccination.
  • Even after vaccination, individuals, particularly those who are immunosuppressed, should follow public health guidelines to protect themselves from infection. These include masking and physical distancing.
  • Individuals on certain treatments have been observed to have decreased antibody responses after vaccination, therefore additional doses have been recommended by the CRA.

The latest findings in people with inflammatory bowel disease (IBD)

Nearly 300,000 Canadians suffer from inflammatory bowel disease (IBD). These individuals are often initially treated with anti-inflammatory and immune-suppressant drugs to decrease inflammation and prevent further disease flare-ups.

CITF-funded research in IBD demonstrated that:

  1. Vaccine uptake is higher in people with IBD than in the general population
    • As of January 2022, 88.6% of SUCCEED participants with IBD had received two vaccine doses and 58.3% had three doses (versus 83.8% and 44.3% of people in the general population) (11).
    • Persons with IBD aged 18 to 39 years were the least likely to receive a third dose, but had higher vaccine uptake rates than the same age group in the general population (11).
  1. Additional doses of COVID-19 vaccine induce strong immunity in individuals with IBD
    • SUCCEED research led by Dr. Gilaad Kaplan indicated that over 99% of people with IBD developed an antibody response against the spike protein after a three-dose vaccine regimen (12).
    • The antibody responses after three doses were more durable compared to the responses after the second dose. High titers of antibodies were observed eight weeks post-dose three. The same remained true following the fourth vaccine dose (13, 14).
    • Starting at least one week following the third dose, anti-S antibody concentrations were found to decay at a rate of about 12% per week (12).
  2. Factors affecting vaccine-induced immunity in people with IBD
    • After three doses of vaccine, anti-S antibody responses were consistently higher than after two doses in persons on any IBD therapy, including biologics and anti-metabolite therapies. However, corticosteroid use at the time of vaccination was associated with reduced levels of anti-S antibodies (12).
    • Neither sex, type of IBD, nor vaccine product were clearly associated with anti-S antibody levels after the third dose (12, 14).
    • According to Dr. Bernatsky’s research, older age was associated with a decrease in anti-S antibodies after the third dose. Meantime, a gap of more than 22 weeks between the second and third doses was associated with a more robust post-third dose antibody response (15).
    • Persons with IBD who received three doses of vaccine and who were previously infected by SARS-CoV-2 had higher concentrations of anti-S antibodies than those who were never infected (12). The same was true for persons with IBD that received four mRNA doses and who were previously infected (13).


Dr. Kaplan contributed to the COVID-19 and IBD Task Force and Crohn’s and Colitis Canada guidance, recommending that IBD individuals follow public health guidelines. The Crohn’s and Colitis Canada website presents an array of scenarios, ranging from low to high risk, but generally advocates that, regardless of vaccination status, individuals should continue:

  • Social distancing.
  • Wearing a mask in closed indoor spaces, and;
  • Good hand hygiene.

This advice is especially important for persons with IBD taking immunosuppressants.

  • Crohn’s and Colitis Canada supports a fourth dose of a COVID-19 vaccine for individuals with IBD who are immunocompromised by their medications, while studies establishing the ideal timing between doses are pending, they recommend following the provincial health authorities time recommendations of 3-6 months between third and fourth doses.
  • ​Crohn’s and Colitis Canada recommends a fourth dose of a COVID-19 vaccine for those who have been taking systemic steroids (prednisone, methylprednisolone, hydrocortisone) at any time after their first COVID-19 vaccine. Steroids have been demonstrated to result in a faster decrease in antibodies to COVID-19 in vaccinated individuals. In someone who has used steroids, the fourth dose of the COVID-19 vaccine should be given three months after the third dose. In someone who is currently using steroids (>20 mg/day, or in children >0.5 mg/kg/day), the fourth dose of COVID-19 vaccine should be given one to three months after the 3rd dose.
  • Crohn’s and Colitis Canada also recommends a fourth dose of a COVID-19 vaccine in people with IBD with moderately or severely active inflammation, moderate or severe malnutrition, or require parenteral nutrition (intravenous nutrition through a central line).
  • Unimmunized people with IBD should receive the COVID-19 vaccine immediately. Vaccines have proven effective at preventing severe COVID-19 (hospitalization, death) in individuals with IBD, even against variants of concern.

The latest findings in transplant recipients

In Canada, an estimated 3,000 transplant procedures are performed annually and 40,000 people are living with a transplant (16) (17). The incidence of COVID-19 in solid organ transplant recipients (SOTR) is ~15-fold higher than in the general immunocompetent population (18), and SOTRs with COVID-19 appear to be at higher risk of severe outcomes on the basis of their chronically immunosuppressed state and underlying medical comorbidities.

  1. SOTRs can mount cellular immune responses after exposure to the SARS-CoV-2 virus
    • According to the CITF-funded PREVenT-COVID study (PRospective Evaluation of COVID-19 Vaccine in Transplant Recipients: A National Strategy), led by Dr. Deepali Kumar, SOTRs were able to mount SARS-CoV-2-specific humoral (antibody) and cellular immune responses (CD4 and CD8 T-cells) following a SARS-CoV-2 infection (19).
    • Compared to SOTRs with more severe disease outcomes, those with mild COVID-19 outcomes, (defined as a lower World Health Organization (WHO) disease score), had higher levels of anti-S CD4 and CD8 T cells that can perform multiple functions (19).
    • This study also shows that two doses of mRNA vaccines induced lower levels of polyfunctional T cells in SOTRs compared to what was induced by a SARS-CoV-2 infection (19).
    • More transplant recipients demonstrated positive anti-RBD responses and neutralizing antibodies after the second vaccine, but as many as 30% of the SOTRs with anti-RBD antibodies showed no detectable neutralizing antibodies after their second vaccine dose (20).
    • More transplant recipients had T-cell responses after the second vaccine dose when compared to the first, but >50% still did not have COVID-19 specific T-cells after the second dose (20). However, even patients with no detectable anti-RBD antibodies were still able to mount robust CD4+ T cell responses, highlighting that vaccination can still have effects in this population (22).
  1. Additional doses of vaccine are required to elicit an immune response and protect against severe outcomes in transplant recipients
    • The latest results from the PREVent-COVID study from Dr. Deepali Kumar (not yet published) highlight that three or four doses of vaccine are safe and effective at protecting against severe infections, hospitalization, or death in SOTRs (21).
    • The study also mentions that the anti-RBD antibody titers increased with each dose. Yet, ~21% of the patients did not show any significant antibody responses following their third dose.  Factors such as older age, lung transplantation, chronic kidney disease, and shorter duration since undergoing a transplant were associated with decreased immunogenicity (21).
  1. Having already had COVID-19 is not sufficient to protect SOTRs from another (Omicron) infection
    • Unvaccinated transplant patients with an early, non-Omicron SARS-CoV-2 infection may be at high risk for symptomatic or severe Omicron infection, owing to comparatively lower antibody and CD4+ T-cell responses to the BA.1 variant (22).
    • Transplant recipients in the PREVent-COVID study infected with the wild type, Alpha and Delta strains of SARS-CoV-2 (either unvaccinated or with one dose of vaccine) demonstrated lower neutralizing capabilities against Omicron (BA.1 and BA.2). However, several patients who were negative for BA.1 showed neutralizing capabilities against BA.2 (45.7%) (22).
    • Similarly, most patients demonstrated spike-specific CD4+ T-cell responses to the wild type, but the T-cell response to the Omicron BA.1 variant in these patients was comparatively lower (22).
  1. Best protection from infection with by Omicron comes from hybrid immunity (a combination of infection and vaccination)
    • Triple-vaccinated transplant recipients (any transplant type) displayed the lowest neutralizing antibody titers compared with transplant patients infected by non-Omicron variants (mostly unvaccinated) or with Omicron BA.1 (vaccinated) (22).
    • Vaccinated transplant recipients from the PREVent-COVID study who recovered from an Omicron BA.1 infection developed potent neutralizing antibodies and T-cell responses at levels similar to those of triple-vaccinated immunocompetent individuals. This included cross-reactive protective immune responses against BA.2 (22).
    • Vaccinated transplant recipients who recovered from Omicron BA.1 displayed robust immune responses to BA.1 and BA.2, and wild type virus. Most developed strong neutralizing antibodies and CD4+ T cells against the wild type and BA.1 strains even when compared to a healthy population that was triple vaccinated (22).
    • The latest findings from The PREVent-COVID study show that patients with at least three doses were protected from hospitalization when experiencing breakthrough infections (predominantly from Omicron). Significantly increased anti-RBD antibody levels were observed in patients who received three doses and had breakthrough infection (predominantly with Omicron) (19).


Dr. Deepali Kumar recommends:

  • SOTRs should receive three doses of mRNA vaccine for their primary series and then receive a bivalent vaccine booster at least three months after the last dose.
  • Transplant recipients should continue to mask in public places and avoid crowds.
  • Instead of limiting social interactions, patients must ensure that everyone around them is vaccinated and do not have COVID-19 symptoms.
  • Patients should receive a dose of Evusheld Evusheld is a monoclonal antibody drug. Monoclonal antibodies attach themselves to the COVID-19 virus and stop it from entering the cells in your body. for an extra layer of protection against the currently circulating BA.5 Omicron variant.

Stem cell transplant recipients

Clinicians in Canada perform approximately 2,000 stem cell bone marrow transplants per year, 200 of which are in children (23).

  1. Receiving a third dose of vaccine yields better protection than the initial two-dose vaccine regimen
    • Kumar’s study showed that in the case of allogenic stem cell transplantIn allogeneic SCT, stem cells are taken from a donor and transplanted into a recipient (Allo-SCT) recipients, a third dose of vaccine promoted better humoral responses than an initial two dose series, without increasing the risk of graft-versus-host disease or other severe adverse effects. Nearly 90% of Allo-SCT recipients developed anti-RBD antibodies after their third dose (24).
    • She also highlighted that a third dose resulted in stronger cell-mediated immunity in Allo-RCT recipients. Most developed antigen-specific CD4+ (between 55% and 80% depending on cell subtype) and CD8+ T-cells (80%) after the second dose of vaccine. These proportions remained as high, or increased slightly, after the third dose (24).

Kidney transplant recipients

The mortality rate in kidney transplant recipients with COVID-19 is between 20% and 28%, compared to 1%–5% in the general population (18). Among the spectrum of SOTRs, some CITF-funded research specifically studies kidney transplant recipients (KTR).

  1. Third vaccine doses are effective, but not as potent against the Omicron variant
    • A CITF-funded study led by Drs. Matthew Oliver and Michelle Hladunewich showed that third doses help mount robust antibody responses in KTR patients (25).
    • Among KTRs, one month after the third vaccine dose, the level of binding and neutralizing antibodies produced was several-fold lower against Delta and Beta, and even more so for Omicron, as compared to the response elicited against the wild type virus. Those with detectable neutralizing antibodies against Omicron achieved antibody levels comparable to healthy individuals who did not have transplants. Three months after dose three, the levels of neutralizing antibody titres were further decreased (25).

The latest findings in people with chronic kidney disease (CKD)

According to the Kidney Foundation of Canada, 1 in 10 Canadians have kidney disease, amounting to a total of 4 million people (26). More than 50,000 Canadians are being treated for kidney failure, with 58% on dialysis and 42% receiving a functional transplant (26).  One study showed that the crude mortality rate was 44.6% in CKD patients with COVID-19, compared to 4.7% in CKD patients without COVID-19 (27). The risk of hospitalization increased in CKD patients with COVID–19 compared to those without CKD (risk ratioRisk Ratio (RR): compares the risk of a health event (disease, injury, risk factor, or death) among one group with the risk among another group. A value greater than 1 means increased risk of the health event. RR = 1.63 (28)).

  1. Vaccines are safe for dialysis patients
    • Oliver and Hladunewich found that vaccines were safe and well-tolerated after both the first and second doses among all CKD participants (29).
    • Also, no serious adverse effects following vaccination were reported in this population (30).
  1. In most dialysis patients, two doses of vaccine induce immune responses and protect against severe outcomes
    • Oliver and Hladunewich observed that a second COVID-19 vaccine dose induced more robust immune responses than the first vaccine dose (29).
    • Among dialysis patients from their study who were infected with SARS-CoV-2, the risk of hospitalization (52% versus 30%) and the mortality rate (16% versus 10%) were higher in the unvaccinated group than among those who received two vaccine doses (31).
    • Among those receiving maintenance dialysis, two doses of Pfizer or Moderna vaccine reduced the risk of SARS-CoV-2 infection by 69% and severe outcomes by 83% (31).
  1. The original monovalent Moderna vaccine offered advantages over the monovalent Pfizer vaccine
    • At six to seven weeks post-second dose, median spike antibody levels were significantly higher for those vaccinated with the monovalent Moderna vaccine than with the monovalent Pfizer vaccine, but the levels of anti-RBD antibodies did not differ substantially between these groups (30).
    • At 12 weeks post-second dose, spike antibody levels had waned more in those who received the monovalent Pfizer compared to the monovalent Moderna. At this timepoint, anti-RBD antibody levels were also lower in participants vaccinated with Pfizer than Moderna (30).
  1. Some dialysis patients fail to mount robust immune responses despite vaccination
    • Some dialysis patients fail to mount an adequate response to two doses, indicating that careful and ongoing monitoring of this patient population is imperative (29).
    • In an editorial review, Drs. Oliver and Peter Blake highlighted that, in the pre-Omicron era, for the dialysis population, COVID-19 vaccination provides moderate protection against acquiring SARS-CoV-2 infection, but is highly protective against severe outcomes. However, effectiveness is still substantially lower than among healthier participants, where the studies reported a VE of 94%–95% for preventing symptomatic infection and 89% for severe infection (32).
    • Oliver and Hladunewich also showed that individuals were at higher risk for SARS-CoV-2 infection if they were from a racialized community, were on dialysis for a shorter period of time, lived in a long-term care facility, or resided in a region with a higher community rate of infection (31).
  1. Booster doses further reduced the risk of severe outcomes
    • During the pre-Omicron era, the risk of being infected with SARS-CoV-2 was 59%, 71% and 78% lower among CKD patients who received one, two, or three vaccine doses, respectively. Similarly, the risk of COVID-19-related hospitalization or death was 53%, 84% and 90% lower among those vaccinated with one, two, or three doses, respectively (33).
    • In CKD patients who received three doses of vaccine, the risk of SARS-CoV-2 infection was 83% less in patients with eGFRThe estimated glomerular filtration rate (eGFR) is a test that measures your level of kidney function and determines your stage of kidney disease. A low eGFR number indicates reduced kidney function. People with a lower eGFR are at increased risk of having chronic kidney disease (CKD) progress to kidney failure. eGFR for a normally functioning kidney is ≥60 ml/min/1.73m2 <30 ml/min/1.73m2 compared to 73% decreased risk in patients with eGFR ≥30 ml/min/1.73m2 (33).
    • Vaccine effectiveness amongst patients with CKD was similar across age, sex, presence of comorbidities, and baseline history of immunosuppressive medication use (33).


Drs. Oliver and Hladunewich recommend that patients with CKD should still be encouraged to take precautions and continue to receive recommended booster vaccinations, because the risk of hospitalization and mortality is still substantial even though data shows that both the third dose and prior infection are protective.

The latest findings in people with cancer

An estimated 233,900 new cancer cases and 85,100 cancer deaths are expected in Canada in 2022 (34).

  1. Boosters are effective against the majority of cancers
    • In patients with solid tumors, neutralizing responses against Omicron following a third dose of mRNA vaccine were higher than for those who received only two doses. The immune response following vaccination, as measured by neutralizing antibodies to the Omicron variant, showed no difference in those patients with or without anti-PD-1/PD-1 treatmentTreatments that help the body recognize and attack cancer cells. (35).
    • In another study of patients with solid tumors undergoing treatment for their cancer, 62.3% of patients still had evidence of cell-mediated immunity against SARS-CoV-2 six months after their third dose (36).
    • About 80% of patients with haematological malignancies did not have neutralizing antibodies against Omicron after two vaccine doses (Pfizer or AstraZeneca), but 45% of them developed detectable neutralizing antibodies after a third dose with the Pfizer vaccine (38)
    • In patients with cancers of the immune systems, such as chronic lymphocytic leukemiaChronic lymphocytic leukemia is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell) or small lymphocytic lymphomaSmall lymphocytic lymphoma is an indolent (slow-growing) non-Hodgkin lymphoma that affects B cells., who failed to respond to two doses of the Pfizer vaccine, less than a quarter (24%) produced SARS-CoV-2 antibodies following a third dose (37), indicating that they are still at higher risk of SARS-CoV-2


The Canadian Cancer society recommends:

  • People with cancer may be at an increased risk of more severe outcomes from COVID-19.
  • People with cancer should get all doses of COVID-19 vaccine that they are eligible for as soon as possible.
  • Patients should continue to follow public health measure including masking, physical distancing, and proper hand hygiene.

Table 1. Impact of COVID-19 on various health conditions

Health Condition Total Number of People in Canada (38.6 million in 2022) Impact of COVID on disease conditions
People living with HIV 62,050 people living with HIV (2018) (38) People living with HIV had a 24% higher risk of SARS-CoV-2 infection and a 78% higher risk of death from COVID-19 than people without HIV (39).
Immune-mediated inflammatory Diseases (IMIDs) >7 million Canadians suffer from IMIDs Rate of COVID-19 related deaths – 8.27 per 1000 person-years compared to 4.88 in general population.

Rate of COVID-19 related critical care admissions or deaths – 8.89 per 1000 person-years in comparison to 5.29 in general population.

Rate of COVID-19 related hospital admissions – 14.31 per 1000 person-years in comparison to 8.77 in general population (40).

Rheumatoid arthritis (RA) Approximately 374,000 (1.2%) Canadians aged 16 years and older were living with diagnosed rheumatoid arthritis in 2016–2017 (41)
  • Rate of COVID-19 related deaths – 13.61 per 1000 person-years
  • Rate of COVID-19 related critical care admissions or deaths – 14.23 per 1000 person-years compared to 4.88 in general population
  • Rate of COVID-19 related hospital admissions – 20.95 per 1000 person-years  in comparison to 8.77 in general population.Reference: (40)
Ankylosing spondylitis (AS) An estimated 300,000 Canadians had AS in 2019 (42).
Psoriasis and psoriatic arthritis 1 million Canadians were affected by psoriasis in 2022 (43).  About 0.25% of Canadians have or may have psoriatic arthritis (PsA), but the exact numbers are unknown. Doctors do know that PsA is diagnosed in about 30% of patients attending psoriasis clinics. PsA were also detected in about 15% of people with psoriasis seen by family doctor in 2017 (44).
Inflammatory Bowel Disease (IBD) 300,000 people were living with IBD in 2018 (45)
  • Rate of COVID-19 related deaths –7.22 per 1000 person-years compared to 4.88 in general population
  • Rate of COVID-19 related critical care admissions or deaths – 7.83 per 1000 person-years in comparison to 5.29 in general population
  • Rate of COVID-19 related hospital admissions – 14.24 per 1000 person-years in comparison to 8.77 in general population.Reference: (40)
SOLID organ transplant Recipients (SOTR) A total of 2,782 solid organ transplants were performed in Canada in 2021 (46). 40 000 people are living with a transplant (16).
  • The incidence of SARS-CoV-2 infection is similar or slightly higher compared with the general population (47).
  • The rate of hospitalizations is estimated to be 4% higher among people with SOTR when compared to healthy individuals (47). However, among those who require hospitalization, the risk for mortality appears to be similar to that for the general population when adjusted for comorbidities (47).
  • Severity of disease appears to be attenuated with the Omicron variant compared with prior variants (48).
Kidney transplant recipients 1, 619 kidney transplants were performed in Canada in 2021 (46). Mortality rate in patients with COVID-19 is between 20% and 28%, compared to 1%–5% in the general population (18).
Chronic kidney disease (CKD) Between 1.3 and 2.9 million Canadians were estimated to have CKD in 2013 (49).
  • COVID-19 incidence was 4.1% compared to 0.5% in the general population.
  • The crude mortality rate was 44.6% in CKD patients with COVID-19, compared to 4.7% in CKD patients without COVID-19 (27).
  • The risk of hospitalization is estimated to be 63% higher in patients with SARS-CoV-2 infection and CKD compared to those without CKD (Risk ratioRisk Ratio (RR): compares the risk of a health event (disease, injury, risk factor, or death) among one group with the risk among another group. A value greater than 1 means increased risk of the health event.  = 1.63) (28).
Cancer There were 157,245 new cases of cancer in Canada, excluding Quebec in 2018 (50). The mortality rate of cancer patients with COVID-19 was higher than that of those without cancer (RR= 1.8) (51).


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