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Dec 27, 2023 · Public health measures can include: personal measures such as self-monitoring, isolation, and quarantine. general recommendations such as hand hygiene, non-medical mask use, physical distancing. community measures such as public messaging and education campaigns.
- On this page
- Preamble
- Introduction
- Transmission of COVID-19
- Public health measures
- Adherence to public health measures
- Conclusion
- Footnotes
- References
•Preamble
•Introduction
•Transmission of COVID-19
•Public health measures
•Adherence to public health measures
•Conclusion
This evidence summary provides an overview of and supporting evidence for the public health measures (PHMs) that can help to reduce transmission of SARS-CoV-2, the virus that causes COVID-19, in community-based settings, places where people live, work, learn and play. It replaces the individual and community based measures guidance (last updated on August 11, 2021) with a summary of current scientific evidence that supports the Public Health Agency of Canada's (PHAC's) guidance for COVID-19 PHMs. It also identifies knowledge gaps in evidence related to PHMs for COVID-19 and where emerging evidence will continue to inform the pandemic response and transition planning. The information in this summary reflects current evidence and may be updated as new evidence becomes available. This summary does not provide practical recommendations and can be used to support decision-making for the implementation of PHMs.
There are evidence gaps on the effectiveness of PHMs as applied in First Nations, Inuit and Métis communities and remote and isolated communities. However, despite these gaps, it is important to consider various well-known social, environmental and economic factors when implementing PHMs in these communities, including housing, water quality or access, food security, pre-existing health conditions, precarious employment, education, income, and access to health care. Additional information can be found in the guidance for COVID-19 and Indigenous communities.
Information for health care settings, and long-term care, including workers in these settings, is out of scope for this document. For information regarding public health and infection prevention and control measures in these settings, readers are advised to refer to the relevant infection prevention and control guidelines.
The primary audiences for this document include federal/provincial/territorial (FPT) and regional/local public health authorities (PHAs), and other health professionals who provide advice to their clients related to PHMs. Operators of non-health care community-based settings accessible to the public (e.g. workplaces, businesses, schools, and recreational settings) may also benefit from information provided in this document, in addition to an available risk assessment and mitigation tool.
The responsibility and legislative authority for implementing PHMs belong to the relevant provinces and territories (PTs) and local PHAs, with the exception of international borders and travel-related advice or policies, for which the federal government is responsible. Consequently, when recommending or implementing PHMs, this document should be considered in conjunction with relevant PT and local legislation, regulations and policies, which should take into consideration existing treaties, agreements, relationships, and capacities within the First Nations, Inuit and Métis communities.
Where applicable and based on context, 'COVID-19' will be used generally throughout this document to refer to the SARS-CoV-2 virus or resulting disease.
The pandemic response goal is to minimize serious illness and overall deaths while minimizing societal disruption as a result of the COVID-19 pandemic. This goal and associated objectives are outlined in the Federal/Provincial/Territorial Public Health Response Plan for Ongoing Management of COVID-19.
Public Health Measures (PHMs) are interventions that can be implemented to help reduce the transmission of COVID-19 in communities. PHMs that can reduce COVID-19 transmission range from actions taken by individuals (e.g., wearing a mask, staying home when sick), to actions taken in community settings and workplaces (e.g., improving ventilation, policies promoting physical distancing), to even more restrictive population-based measures that can have considerable impact and require specific jurisdictional authority to implement (e.g., school closures, gathering size restrictions, business closures). For example, individuals can choose to wear masks to protect themselves and others, representing an individual-level PHM; while mask promotion policies in public settings would be considered a community-level PHM.
PHMs are usually implemented in combination, often referred to as "layering", as combinations of PHMs are more effective than single measures on their own, especially when implemented as early as possible.
The focus of this evidence summary is on non-pharmaceutical measures, rather than pharmaceutical interventions such as COVID-19 vaccines, antivirals, and therapeutics. While pharmaceutical interventions are not addressed here, more information can be found on the Vaccines for COVID-19 and COVID-19 treatments webpages on Canada.ca.
Although preventing all cases of COVID-19 is not the main public health goal at this point in the pandemic, evidence-informed PHMs are recommended for individuals and communities to help lower transmission of COVID-19, in order to:
•Reduce the number of people who experience severe illness and death due to COVID-19;
The effectiveness of PHMs in reducing transmission of COVID-19 is directly linked to the ways that COVID-19 is transmitted from a person who is infected to others. This section provides some of the evidence about the modes of transmission of COVID-19, and the context for the PHMs that can effectively reduce the risk of transmission. The relative role of the different modes of transmission for COVID-19 remains unclear.
COVID-19 vaccines have had, and continue to have, an effect on transmission of COVID-19 in Canada and globally; directly by reducing the risk of COVID-19 transmission from those infected, and indirectly by reducing rates of infection and symptomatic disease. The evidence continues to emerge on these topics, including waning immunity over time, the effect of booster doses, and vaccine effectiveness for various VOCs; however, COVID-19 vaccines are not the focus of this evidence summary. For more information, refer to Vaccines for COVID-19 and COVID-19 vaccine: Canadian Immunization Guide.
Face masks
Masks play an important role in reducing the risk of transmission of respiratory infections, such as COVID-19. Observational studies have shown a reduction in the incidence of COVID-19 infection in individuals wearing masks compared to those who did not wear masks.Reference 59Reference 60Reference 61Reference 62Reference 63 Medical masks (MMs) (such as surgical/procedure masks) and respirators, can reduce transmission of droplets and some aerosols from someone with COVID-19 to others (i.e., source control).Reference 59Reference 64 They can also provide protection to the wearer by reducing the risk that they will inhale infectious respiratory particles when exposed to someone who is infected (i.e., protection from infection).Reference 59Reference 63Reference 65 Results of observational studies and controlled trials comparing the effectiveness of MMs and respirators are mixed, with some studies suggesting no significant difference in protection when using a MM compared to a respirator, and others suggesting a greater protective effect from respirators.Reference 59Reference 66Reference 67 Respirators typically offer a better fit, giving them an advantage over medical masks which often have gaps between the mask and the face. MMs and respirators are regulated as Class I medical devices by Health Canada and must meet standards for characteristics such as particle filtration (i.e. filtration efficiency), pressure differential, flammability, and possible fluid resistance. Non-medical masks (NMMs) provide some level of source control and may also protect the wearer from exposure to infectious particles to varying degrees.Reference 59Reference 68 There are a wide range of NMMs available in Canada, from tightly woven fabric materials made with various numbers of layers, pockets, and filtration layers; to those that are made from synthetic polymers (e.g., melt-blown filtration materials) and look very much like MMs and respirators. Performance of NMMs is highly variable and dependent upon their construction and fit.Reference 59Reference 68 NMMs have generally been shown to be less effective than MMs or respirators, for both source control and protection for the wearer.Reference 59Reference 66 NMMs are not regulated in Canada and there are no national standards. Some NMMs commercially available in Canada may meet standards for NMMs established by the Bureau de normalisation du Québec, or those in other countries (e.g., ASTM F3502-19, CEN CWA 17553:2020, AFNOR Spec S76-001). There are several factors that affect the effectiveness of masks, mainly fit, filtration efficiency and breathability.Reference 59Reference 66Reference 68 Of these factors, fit is considered to have the largest impact on the effectiveness of a mask.Reference 68Reference 69 Masks that are loose fitting or gaping away from the face have been found to have lower efficacy compared to tight-fitting masks with no gaps.Reference 70 Several methods have been identified for improving mask fit, and subsequently mask performance, including the modification of ear loops, tucking in the sides of a MM, and using a mask fitter over top of a mask.Reference 71Reference 72 Layering a cloth mask over a MM has also been identified as a method for improving mask fit and performance.Reference 72 Filtration efficiency refers to the ability of a mask to reduce particle penetration through the mask fabric and is another key driver of performance.Reference 59Reference 66 Laboratory studies indicate that respirators have the highest filtration efficiency, generally 95% or higher for certified respirators, followed by MMs and then NMMs.Reference 59Reference 66Reference 69 Although the filtration efficiency of NMMs is reported as being lower than MMs and respirators, it varies widely and is heavily dependent upon the materials and methods used to construct the mask.Reference 59Reference 66Reference 69 Studies have found that filtration efficiency is dependent on the fabric's quality (e.g., tightness of the weave, fibre or thread diameter) and inherent characteristics of the fabric (e.g., electrostatic charge and ability to withstand moisture).Reference 66Reference 68 Masks with multiple layers have a higher filtration efficiency compared to single layer masks, and the addition of a middle layer of filter-type fabric has been shown to increase filtration efficiency.Reference 68 There are few studies that discuss the impact of breathability on transmission risk; however the filtration efficiency of a mask must be balanced with its breathability. NMMs constructed of more than three layers or made with non-porous materials have been found to have very poor breathability, and are unlikely to be well tolerated.Reference 68Reference 73 PHAC provides recommendations for individuals on mask use, including when masks should be worn, how to select a mask, and how to wear a mask properly. Face mask use at the community level Ecological studies have suggested that the implementation of community-based masking policies at national and regional levels is associated with decreased COVID-19 incidence, hospitalization, and mortality.Reference 66Reference 74 These ecological studies, along with numerous modelling studies, estimate that universal mask wearing in a community can lead to a decrease in COVID-19 transmission, particularly when adherence is high.Reference 75 However, many ecological studies do not report on adherence to masking policies or on the types of masks used in the community, making it challenging to compare masking policies in different communities. Masking policies can also be implemented within specific settings, such as schools and workplaces. Schools with mask requirements have been shown to have lower levels of COVID-19 transmission compared to schools without mask requirements; and some evidence suggests a reduction in COVID-19 transmission in work and community settings, such as meatpacking plants and hair salons, when masks are used and layered with other PHMs.Reference 76Reference 77Reference 78Reference 79Reference 80Reference 81 This evidence suggests that mask use may be beneficial in other environments where individuals are in close contact for extended periods of time, such as congregate living settings and on public transportation. Information on mask use in workplaces can be accessed through the Canadian Centre for Occupational Health and Safety.
Ventilation
Current evidence suggests proper ventilation of indoor settings is a key PHM for limiting the transmission of COVID-19.Reference 12Reference 14Reference 18Reference 82Reference 83 Ventilating a room or indoor space involves diluting and replacing potentially contaminated indoor air with air from the outdoors, either through natural or mechanical means.Reference 82Reference 83 Results from epidemiological, experimental, and modelling studies have shown that factors such as ventilation, airflow, air filtration, and access to fresh air play an important role in reducing COVID-19 transmission in any indoor setting.Reference 82Reference 84Reference 85Reference 86Reference 87 During the COVID-19 pandemic, many outbreaks and superspreading events have taken place in indoor settings where ventilation and airflow were restricted or poor, highlighting the importance of this PHM.Reference 13Reference 19Reference 28Reference 29Reference 30Reference 31Reference 32Reference 33Reference 34Reference 35Reference 36Reference 86 Natural ventilation, which involves opening multiple exterior windows and doors of a space or a building to remove potentially contaminated indoor air, has been shown to be an effective, low-cost way to reduce the risk of COVID-19 transmission, especially in settings and older buildings where effective mechanical ventilation is not available.Reference 12Reference 82Reference 83 Opening windows and doors can help create a directional airflow from the outdoors that moves through a space and dilutes and exhausts indoor air, limiting the potential accumulation of infectious aerosols.Reference 12Reference 82Reference 83 It is important that the indoor air is expelled, and not just circulated within the space.Reference 88 Natural ventilation may be limited by settings that do not have opening windows, outdoor air quality, and climatic conditions (e.g., weather, outdoor air pollution, levels of pollen and other irritants).Reference 83 Mechanical ventilation via the use of heating, ventilation, and air conditioning (HVAC) systems, has been shown to reduce the risk for COVID-19 transmission in indoor spaces.Reference 83 Mechanical ventilation is most effective when HVAC systems are properly configured for:Reference 82Reference 85Reference 87 Maximum fresh air input and air changes; Operation beyond times of occupancy or continuous use to help flush out potentially infectious indoor air; Filters with the highest Minimum Efficiency Reporting Value (MERV) rating that the system can handle and that are routinely changed as recommended by the manufacturer; The type of setting and activity; and The number of occupants. Evidence supports the effectiveness of ventilation in reducing the risk of COVID-19 transmission beyond residential settings. The same measures and principles when applied to non-residential settings (e.g., schools, workplaces, commercial spaces, retail areas) have been shown to decrease the risk for COVID-19 transmission, especially when used in conjunction with other effective public health measures (e.g., universal masking).Reference 11 Natural or mechanical ventilation may not always be possible within all settings due to structural or economic constraints. For example, older buildings may not have a functioning HVAC system, or windows that can open. The significant cost of implementing and operating a mechanical ventilation system in buildings may present a financial barrier for some facility operators. In these situations, where natural or mechanical ventilation is not possible or cannot be improved, evidence indicates that air filtration, via the use of portable air purifiers, can help to reduce the concentration of COVID-19 virus in the air.Reference 89Reference 90Reference 91Reference 92Reference 93 Portable air purifiers are most effective when equipped with a high-efficiency particulate air (HEPA) filter and appropriately sized for the room in which it will be used.Reference 87Reference 88Reference 89Reference 90Reference 91 Although using air purifiers indoors can add an additional layer of protection, they should be used alongside other individual PHMs. Ultraviolet germicidal irradiation (UVGI) has been proposed as a method to inactivate the SARS-CoV-2 virus in the air or on surfaces and objects. While UVGI has been shown to be effective against SARS-CoV-2 in laboratory settings and simulation studies, there is little evidence available to support claims that this is an effective tool to reduce the risk for COVID-19 transmission in real-world applications.Reference 94Reference 95Reference 96Reference 97 Measurement of carbon dioxide (CO2) levels has been proposed as a surrogate for determining how well a room is ventilated, given that high CO2 levels may be an indicator of low air changes within a space.Reference 98 However, a low level of CO2 in an indoor space does not necessarily mean that the risk of COVID-19 transmission is low, and CO2 levels alone do not reflect all transmission risks. Evidence is still limited on the effectiveness of monitoring CO2 levels for reducing the risk of COVID-19 transmission. PHAC provides recommendations on how to improve ventilation in the context of COVID-19, and guidance on indoor ventilation during the COVID-19 pandemic.
Physical distancing and reducing contacts
Physical distancing, where some specified distance between individuals is maximized or maintained, is another PHM that can reduce the risk of transmission of COVID-19.Reference 15Reference 99 Physical distancing recommendations for COVID-19 were originally developed and implemented based on observations that close-range transmission is more common than long-range transmission for influenza, COVID-19, and certain other respiratory infectious diseases. Transmission across longer distances is likely less efficient than at shorter distances, as there is a greater likelihood for a person to be directly exposed to a larger dose of virus at close range.Reference 9Reference 13Reference 15 Close contact exposures increase risk of transmission as respiratory particles containing the SARS-CoV-2 virus tend to be more concentrated closer to someone who is infected.Reference 13 Evidence shows that physical distancing of at least one metre lowers the risk of COVID-19 transmission compared to distances of less than one metre, but distances of two metres could be more effective, suggesting that protection against COVID-19 transmission is increased as distance is increased.Reference 99Reference 100Reference 101 Generally, the risk of COVID-19 transmission is lower when the number of interactions between people, the number of individuals involved in each interaction, and duration of each interaction are minimized, and when interactions occur at the greatest distance possible.Reference 9Reference 11Reference 13Reference 15 Clusters and outbreaks in indoor spaces have been reported widely throughout the pandemic, with a lack of physical distancing being one of several factors contributing to COVID-19 transmission.Reference 15 Community-level measures: Physical distancing and reducing contacts Physical distancing at a community level can help reduce COVID-19 transmission. Outbreaks have been a significant source of COVID-19 spread in Canada and point to increased risk in closed and crowded settings, such as long-term care and retirement residences, and congregate living settings (e.g., farmworker residences, homeless shelters, student residences, detention centres, correctional facilities), where physical distancing can be more difficult.Reference 102Reference 103Reference 104Reference 105 This also highlights the risk for Indigenous communities, particularly those that are remote and isolated, which typically experience higher rates of overcrowding and poor housing conditions. Physical distancing can be implemented at the community level when businesses, restaurants, and schools implement policies and provide tools (e.g., signage and floor markers) to ensure that individuals are able to safely distance. In schools, physical distancing is a supplementary measure that can be used in combination with other PHMs to reduce COVID-19 transmission, especially during outbreaks or periods of increasing or high transmission. Measures that limit the number of contacts in the community have also been effective at reducing COVID-19 transmission. Transmission events in high-risk community settings, such as sporting events, restaurants, and nightclubs, have been attributed to a high number of close and sustained contacts, further highlighting the importance of reducing crowding in community settings.Reference 106 Observational and modelling studies have shown that when COVID-19 cases rise, gathering restrictions at national and regional levels (e.g., gathering size restrictions, school and workplace closures, occupancy limits in businesses) have played an important role in reducing transmission of COVID-19.Reference 107Reference 108Reference 109Reference 110Reference 111Reference 112 Internal PHAC modelling has shown that restrictive measures that limit contacts, like school and business closures, and gathering size restrictions, are associated with reductions in the number of COVID-19 cases, hospitalizations, and deaths. The Oxford Stringency Index, developed by the University of Oxford and captured in the COVID-19 Government Response Tracker, shows similar patterns in other countries when these types of restrictive measures are implemented.
When PHMs are implemented, they will be less effective at reducing COVID-19 transmission if people are not adhering to recommended or required measures, either by choice or because they are not able to due to life circumstances.
Data from the most recently completed wave of Canada's COVID-19 Snapshot Monitoring Study (COSMO), collected in April 2022, suggest that adherence to PHMs in Canada is moderate to high.Reference 146 Among respondents surveyed, 91% report wearing a face mask when it is mandatory; 57% report wearing a face mask when it is not mandatory; 77% report frequent hand washing with soap or hand sanitizer; 59% report usually practicing physical distancing; and 87% report usually staying home when sick.Reference 146 Data from previous waves of the survey show that the primary motivators for adhering to PHMs include protecting loved ones and the community, protecting oneself, and following recommendations of health experts, scientists and government. Furthermore, anxiety related to family's health, trust in government sources of information, and trust in medical experts were the strongest predictors of adherence to PHMs.Reference 146
Research shows that adherence to PHMs over time may be influenced by a variety of factors, such as housing, working and community conditions; financial and social circumstances (e.g., caregiving responsibilities); attitudes and beliefs (e.g., trust in government, science, and health care; ideologies; social norms); demographic factors; and, cultural and spiritual factors.Reference 147Reference 148Reference 149Reference 150Reference 151 The length of the pandemic and the resulting pandemic fatigue may also affect adherence to PHMs.Reference 152
Research also suggests that the following factors are associated with increased adherence to COVID-19 PHMs: older age, female gender, higher trust in government and science, higher perceived risk of COVID-19, greater use of traditional news media, higher COVID-19 knowledge, increased anxiety, and perceived self-efficacy to adopt public health measures.Reference 153Reference 154 In contrast, non-adherence to PHMs has been shown to be associated with living in a rural area, suffering from depression, belief in conspiracy theories, psychological reactance (i.e., response to the perceived or real threat or loss of a behavioural freedom), narcissism, strong support for personal freedom, and smoking.Reference 154Reference 155Reference 156Reference 157Reference 158Reference 159
Some populations have a higher incidence of negative consequences associated with restrictive PHMs, which may reduce adherence to such measures and consequently lead to ongoing transmission.Reference 55Reference 56Reference 57Reference 58 For instance, lockdowns and business closures can interfere with work, income and access to care; gathering restrictions can reduce access to social supports and networks; and school closures can affect work and education.Reference 1Reference 2Reference 3Reference 4 These measures can lead to greater substance use, mental health issues, and exposure to domestic violence.Reference 1Reference 2Reference 3Reference 4Reference 160 People with physical or mental disabilities, racialized populations, and Indigenous people may be particularly affected as they face greater inequities.Reference 5Reference 6Reference 7Reference 8Reference 55Reference 58Reference 116 Average life satisfaction and the prevalence of high self-rated mental health and high community belonging were all lower among racialized individuals during the pandemic compared to before the pandemic.Reference 162 Some populations may also have reduced capacity to adhere to PHMs due to socioeconomic barriers, such as sub-standard and overcrowded housing, lack of access to potable water, and food insecurity.
In a cross-sectional survey administered to Canadians in May 2020, 90% of respondents reported confidence in their ability to adhere to a variety of PHMs.Reference 149 The survey suggested that those who identified as male, were younger, and in the paid workforce were less likely to consider recommended PHMs as effective, and had less confidence in their ability to adhere to recommended measures.
This summary provides an overview of the evidence available to inform appropriate actions that may help to reduce the risk for COVID-19 transmission among individuals and communities across Canada.
As the evidence is continually evolving, conclusions and approaches may change. For this reason, this summary has focused more on reviewing the current state of evidence, emphasizing those strategies that have a fairly well-established evidence base, and less on the practical application of specific PHMs. Given the jurisdictional role of the federal government in public health, implementation of the PHMs, at local, regional, provincial and territorial levels, is up to local or regional public health authorities and governments. Individuals should always follow the latest recommendations and guidance from their local or regional public health authorities and provincial or territorial governments.
Footnote a
An immune escape VOC may be resistant to available vaccines or natural immunity from prior infection.
Return to footnote a referrer
Footnote b
A superspreading event is defined as an event or gathering where certain individuals infect an unusually high number of secondary cases.
Return to footnote b referrer
Reference 1
Public Health Ontario, "Negative Impacts of Community-based Public Health Measures on Children, Adolescents and Families During the COVID-19 Pandemic: Update," 2021. [Online]. Available: https://www.publichealthontario.ca/-/media/documents/ncov/he/2021/01/rapid-review-neg-impacts-children-youth-families.pdf?la=en. (PDF format) [Accessed 25 January 2022].
Return to reference 1 referrer
Reference 2
Public Health Ontario, "Negative Impacts of Community-Based Public Health Measures During a Pandemic (e.g., COVID-19) on Children and Families," 8 June 2020. [Online]. Available: https://www.publichealthontario.ca/-/media/documents/ncov/cong/2020/06/covid-19-negative-impacts-public-health-pandemic-families.pdf?sc_lang=en. (PDF format) [Accessed 25 January 2022].
Return to reference 2 referrer
Individual public health measures are effective actions you can use every day to help reduce the spread of COVID-19. These measures are also sometimes called personal preventive practices. It's most effective to use several measures at once, which is called layering.
- COVID-19 spreads from an infected person to others through respiratory droplets and aerosols (smaller droplets) created when an infected person: br...
- Evidence indicates that vaccines are effective at preventing serious outcomes due to COVID-19, such as severe illness, hospitalization and death. Y...
- Individual public health measures are actions you can take to help prevent the spread of COVID-19 and other illnesses, like flu. We've previously r...
- As COVID-19 continues to circulate in Canada, governments and public health authorities will continue to: make public health decisions to prevent a...
- The risk of getting COVID-19 is evolving daily and varies between and within communities. Risk is dependent on: how many people in the community ar...
Public health organizations are looking for the latest scientific evidence to inform the COVID-19 response in Canada. Evidence is the available body of facts or information on a topic. There are different types of evidence: research-based, experience and opinion.
COVID-19 is an illness caused by the SARS-CoV-2 virus. It was first identified in late 2019 and declared a global pandemic by the World Health Organization on March 11, 2020. COVID-19 Resources. Visit the Government of Ontario website or your local public health unit for information on: how to get COVID-19 vaccines and boosters.
Nov 25, 2021 · What are public health and social measures? Put simply, public health and social measures are preventive measures at the individual and community level. Preventive measures can be applied at different times and in different combinations to reduce exposure to, and the spread of, COVID-19.
Feb 1, 2023 · Public health and social measures (PHSM) refer to non-pharmaceutical interventions implemented by individuals, communities and governments to protect the health and well-being of communities affected by health emergencies.
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related to: what are public health measures covid 19View safety information for an authorized treatment. FDA Emergency Use Authorization. Download the HCP Fact Sheet and the CDER review for GOHIBIC for more information.
