Pre-existing condition
(eg, chronic disease, immunocompromise, pregnancy, disability) | Differential disease severity has been shown to have large independent associations with chronic medical conditions (heart failure, diabetes, chronic kidney disease, dementia, liver disease) and obesity (body mass index, BMI≥40).10 Differential disease severity has been shown to have moderate independent associations with obesity (BMI>30), and haematological malignancy.10 No clear evidence of an independent association of differential disease severity in pregnancy currently exists10; however, the possibility has been suggested in some studies. People with disabilities may experience differential disease exposure due to challenges with infection prevention and control (IPC) measures† and residence in group home settings.
Multiple possible intersections such as: age, socioeconomic status (SES), place of residence, social capital, racialisation | Include these populations in clinical trials to demonstrate efficacy and safety of interventions (following Research Ethics Board (REB) guidelines and First Nations Principles of Ownership, Control, Access and Possession (OCAP)49 of data collection processes in their communities). Consider these populations as key groups for vaccination. Facilitate rides to immunisation clinics or home visits for those who are immobile to improve access to vaccine and testing for infection. Offer vaccination at healthcare visits for pre-existing conditions (eg, medical specialist appointments). Enable IPC measures† to reduce exposure.
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Place of residence
(eg, remote, overcrowding, homeless, institutionalisation) | Differential exposures in institutions exist with evidence of a high number of outbreaks in long-term care facilities (experiencing the majority of outbreaks), hospitals, prisons, shelters.50 Outbreaks involving large numbers of reported cases have occurred in rural, and remote communities.50 Differential disease severity has been shown to have large independent associations with homelessness.10 Homeless populations, and those living in shelters/group homes or in overcrowded neighbourhoods or homes (eg, migrant workers), as well as rural, remote and Indigenous communities have differential exposure and challenges with physical distancing and other IPC measures†, as well as potentially decreased access to healthcare. Indigenous communities have been disproportionately impacted in previous pandemics (eg, 2009 H1N1 influenza).4
Multiple possible intersections such as: pre-existing condition, SES, education/literacy level, social capital, racialisation | Include these populations in clinical trials of interventions (following REB guidelines and OCAP principles49). Consider these populations as key groups for vaccination. Consider standing orders in institutions, and mobile clinics in hardly reached populations to improve access to immunisation. Enable IPC measures† to reduce exposure. Consider vaccinating all eligible individuals in remote areas facilitated by community members/leaders/advocates for efficient, effective use of resources. Support programmes and policies aimed to assist and empower systemically marginalised populations and improve access to healthcare.
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| Racialisation (including ethno-racial and ethno-cultural diversity, immigration or refugee status) | Differential disease severity has been shown to have large independent associations with some racialised populations.10 Evidence of higher rates of COVID-19 and differential disease severity in ethno-culturally diverse neighbourhoods exists.17–19 Racialised populations have differential access to healthcare, and may experience stigmatisation and discrimination. Lower vaccination rates have been observed in immigrant children and seniors for other vaccine-preventable diseases (VPDs).41 Visible minorities and Indigenous Canadians appear to be less willing than non-visible minorities to get an effective recommended SARS-CoV-2 vaccine.42 Immigrant/refugee populations or migrant workers may have differential exposure due to international travel. Racialised populations are disproportionately represented in precarious jobs and workplace settings such as in the food or healthcare sectors, and often reside in multigenerational living spaces, leading to differential exposure and transmission within communities.
Multiple possible intersections such as: SES, place of residence, occupation, pre-existing conditions, social capital, education/literacy level | Include populations from diverse racial, ethnic and cultural backgrounds in clinical trials (following REB guidelines and OCAP principles49). Address racialised barriers to accessing healthcare and support policies that target systemic racism and protect the rights of racialised groups. Improve access to testing and vaccination (eg, mobile clinics, publicly funded interventions) for racialised populations without further stigmatisation or discrimination, including those without health insurance (eg, migrant workers, asylum seekers). Engage trusted community leaders/partners/elders and liaise with relevant organisations (eg, immigration and refugee departments) in planning for immunisation programmes and communication materials. Provide culturally appropriate educational and communication materials in a variety of languages, media platforms and venues. Have translators and supports (eg, community members) available in clinics. Enable improved IPC measures† to reduce exposure.
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| Occupation | Healthcare workers/personnel have differential exposure and transmission to clients at high risk of severe illness. However, some in this group may have more access to and training in the use of PPE and other IPC measures†, so exposure risk could be significantly reduced compared with other groups.47 48 Essential services workers (eg, emergency workers, grocery/transit staff, meat/agriculture workers, teachers) and others who cannot work virtually as the economy reopens and have high social contact (with limited IPC measures†) have differential exposure. Outbreaks involving large numbers of reported cases have occurred in agricultural work settings, including those with congregate living for migrant workers.50 Individuals who travel internationally for work may have differential exposure.
Multiple possible intersections such as: SES, racialisation, social capital | Include these populations in clinical trials (following REB guidelines and OCAP principles49). Consider these populations as key groups for vaccination. Offer alternate immunisation settings such as mobile, worksite, or after-hours immunisation clinics and testing. Enable improved IPC measures† to reduce exposure.
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| Gender identity/sex | Differential disease severity has been shown to have a large independent association with male sex,10 that may be linked to immunological sex differences or gendered differences in behaviours such as differential access to healthcare before progression of disease. Gendered differences in caregiver roles, gender-based violence and socioeconomic instability may result in differential direct and indirect impacts of the pandemic.
Multiple possible intersections such as: occupation, pre-existing conditions, SES, social capital, risk behaviours | Consider gender/sex-inclusive vaccination policies. Address gendered barriers to accessing healthcare and vaccination programmes (eg, through social influencers). Support sex and gender-based analyses. Support programmes and policies aimed to assist and empower systemically marginalised populations and improve access to healthcare.
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| Religion/belief system | Religious beliefs about immunisation may result in differential access to vaccine. Gatherings of faith-based communities may lead to differential exposure. Outbreaks involving large numbers of reported cases have occurred in mass gatherings,50 and cases linked to religious facilities continue to emerge.
Multiple possible intersections such as: racialisation | Engage faith-based leaders in the development of educational materials and planning for immunisation programmes. Offer alternate immunisation settings such as at places of worship. Enable improved IPC measures† to reduce exposure. Support programmes and policies aimed to assist and empower systemically marginalised populations and improve access to healthcare.
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| Education/literacy level | Those with lower education or literacy levels potentially have decreased access to healthcare. Lower levels of education (or parental education in the case of children) have been associated with lower vaccination rates in all age groups for various VPDs.44 45 Those with lower education or literacy levels are less likely to be able to work from home, potentially leading to differential exposure. International students may have differential exposure if they travel internationally, and differential access to healthcare if not insured.
Multiple possible intersections such as: place of residence, occupation, pre-existing conditions, smoking, SES, racialisation | Offer alternate immunisation and testing settings to improve access (eg, school-based vaccination programmes). Provide educational materials at appropriate literacy levels. Have translators available in clinics. Enlist multilingual family/community members to assist in communication.
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Socioeconomic status (SES)
(including income, and coverage of healthcare and healthcare interventions) | Differential disease severity has been shown to have large independent associations with low socioeconomic status.10 Populations with lower income status and inability to pay for IPC resources, higher risk occupations with limited IPC measures†, job insecurity and inability to work from home have differential exposure. Lack of healthcare insurance or inability to pay for healthcare interventions may result in differential access. Vaccination rates tend to be lower in lower socioeconomic groups for various VPDs even if vaccines are publicly funded.43 44
Multiple possible intersections such as: place of residence, occupation, pre-existing conditions, social capital, education/literacy level, racialisation | Include populations from a variety of SES backgrounds in clinical trials (following REB guidelines and OCAP principles49). Improve access to testing and vaccination (eg, mobile clinics, publicly funded interventions) regardless of healthcare coverage. Enable improved IPC measures† to reduce exposure. Support programmes and policies aimed to assist and empower systemically marginalised populations and improve access to healthcare.
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Social capital
(social support/networks, trust) | Lack of support networks (eg, to remind or enable individuals and caregivers to attend to vaccination and other IPC measures†), and lack of trust (eg, in authorities making recommendations) may lead to differential access to healthcare interventions. Non-vaccination has been associated with single-parent families for other VPDs.44
Multiple possible intersections such as: SES, place of residence, occupation, age, pre-existing conditions, education/literacy level | Empower trusted healthcare providers to recommend and provide vaccinations during patient visits. Improve trust in immunisation and other healthcare interventions through trusted leaders and social media influencers. Implement reminder/recall systems for immunisation. Offer childcare during immunisation visits.
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| Age | All ages are susceptible to COVID-19, but the rate of diagnosed COVID-19 cases generally increased with age earlier in the pandemic. As national lockdown measures relaxed, a significant increase in the proportion of cases in younger adult age groups has been observed.50 Differential disease severity has been shown to have a very large independent association with increasing age.10 Children <10 years of age experience milder or asymptomatic infection but evidence of differential disease severity (ie, multisystem inflammatory syndrome) is emerging.51
Multiple possible intersections such as: pre-existing conditions, social capital, SES | Include populations from a variety of age ranges in clinical trials (following REB guidelines and OCAP principles49). Consider the evidence of inequities related to age when sequencing groups for early vaccination. Consider promotion and education activities on platforms that access key age groups (eg, established social media, print media, mail campaigns in older ages). Consider vaccine programmes to protect those in contact with the elderly if vaccine efficacy is impaired due to immune senescence.
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Other factors
(eg, substance use disorders, smoking) | No large increased risk in hospitalisation in current or former smokers has been observed to date with limited data for associations with substance use disorders.10 However, data continues to evolve. These populations may have differential access to healthcare. Indirect impacts of the pandemic could lead to increased substance use, with increased substance-related deaths and harms.
Multiple possible intersections such as: SES, social capital, place of residence, pre-existing conditions, education/literacy level | Include these populations in clinical trials (following REB guidelines and OCAP principles49). Improve access to testing and vaccination (eg, mobile clinics, at substance use treatment centres) and offer publicly funded interventions. Enable improved IPC measures† to reduce exposure. Support programmes aimed to assist those with tobacco and substance use disorders.
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