Table 2.

Definitions of the terms used

Equity	The absence of avoidable and unfair differences in a particular condition or state between different groups of people. For example, health equity is the absence of avoidable and unfair differences in health outcomes [147]
Adverse effects (adapted from Lorenc and Oliver) [9]
Physical health	Direct or indirect harms that accrue across all spheres of physical health
Psychological health	Direct or indirect harms that accrue across the range of mental health areas, including but not limited to depression, anxiety, stress, and psychosis
Group or social	Direct or indirect harms that accrue by targeting social interventions at particular groups or parts of society, thereby worsening the experience of subsets of people within a population
Opportunity cost	The loss of one or more option, course of action, or outcome that is incurred by selecting an alternative one
PROGRESS domains (adapted from O'Neill et al.) [4]
Place of residence	Place of residence can mean the type of dwelling (house with a garden, flat, house of multiple occupancy, informal settlement, prison), location of dwelling (urban, suburban, rural), specialist dwelling (assisted living, care homes, hospice), or lack of dwelling (people who experience homelessness). It is linked to socio-economic status and access to outside space, public transit, infrastructure, livelihoods, and other services (e.g., health care), social cohesion, and environmental exposures [148]
Race, ethnicity, culture, and language	There are many health outcomes that accrue inequitably due to race, ethnicity, culture, and language. Health risks and outcomes are often stratified between ethnic groups, with worse health outcomes often observed in Black, Asian, and Minority Ethnic (BAME) populations. This may reflect inequities in the burdens of wider determinants of health such as employment and environmental exposures, discrimination, education, or diet. However, concepts such as inherent or biological susceptibility can be invoked to further discriminate against such groups, leading to further physical and psychological harms
Occupation	Occupation may refer to the status of employment—such as unemployed, part-time, “zero-hour” contract or full-time employment—or the type of employment. These have implications for health equity, with some professions or exposures being more high risk than others. Job security and the type of labor protections in place are important, particularly during times of crisis
Gender/sex	Biological and gender-based differences can lead to unequal distribution of disease risks, incidence and outcomes, as well as healthcare service needs. Other differences can be due to inequitable exposure to risk or protections based on sex or gender, such as through the sector of employment or legal rights, or discrimination, barriers to services, or the type and quality of service provision that is received
Religion	Religious affiliation, or lack thereof, can lead to inequitably exposure to harms and/or opportunities. For example religious status may affect access to health services or the appropriateness of the health service offered and received. Certain religious affiliations may experience discrimination, stigma, or even violence
Education	Education is known to have impact on health status not only due to its relationship with employment, and consequently, income, but also due to the colocation and embedding of other health interventions (e.g., counseling and meal programs) into educational settings. Education is a fundamental determinant of health and also an effective means of reducing health inequities. Conversely, disruption to education is an adverse mechanism for potentially increasing inequalities; partly by withdrawing the intervention from poorer families, but also because better off families are better able to fill the gap with supplemental homeschooling
Socioeconomic status (SES)	Higher SES is associated with longer life expectancy and fewer years of poor health due to a constellation of effects including access to clean water, food security, better housing conditions, education, access to healthcare, health and communication literacy, and lower rates of stress
Social capital	The original PROGRESS definitions included social capital, which was defined as: “social relationships and networks. It includes interpersonal trust between members of a community, civic participation, and the willingness of members of a community to assist each other and facilitate the realization of collective community goals and the strength of their political connections, which can facilitate access to services [4].” Social capital can act as a determinant of health and also a social buffer, particularly in times of individual or population-level crisis. It can act via psychosocial pathways, and it can enhance financial support or access to resources [114]. Social capital is closely related to socioeconomic inequalities; it is important not to view social capital, which often has an individualistic focus, as an alternative to effective health, social and economic policies to reduce or even prevent inequities [149]
Other relevant domains: The PROGRESS domains include a “Plus” feature, which allows for the addition of specific time-dependent or condition-dependent domains. These can vary across contexts. We chose to include age and disability because of their relevance to COVID-19 outcomes [4]
Age	While age itself is an unavoidable risk factor for many diseases, certain age groups can often be inequitably impacted by avoidable differences in access to services and technology and vulnerability to exploitation and to the impacts of termination or suspension of certain services such as routine healthcare services or education. Some age groups may have greater resilience or adaptability during times of crisis
Disability	Disability reduces access to health services [150]. These reductions in access may be exacerbated by closures, uncertainties, and reduced availability of primary care clinicians or other forms of routine care. Uncertainty in access to services can lead to psychological harms for those most dependent on them [151]