# Introduction to public health and social measures
What are PHSM? PHSM have been implemented worldwide over the course of the pandemic to suppress SARS-CoV-2 transmission and reduce mortality and morbidity from COVID-19. PHSM include the following: personal protective measures (for example, physical distancing, avoiding crowded settings, hand hygiene, respiratory etiquette, mask-wearing); environmental measures (for example, cleaning, disinfection, ventilation); surveillance and response measures (for example, testing, genetic sequencing, contact tracing, isolation, and quarantine); physical distancing measures (for example, regulating the number and flow of people attending gatherings, maintaining distance in public or workplaces, domestic movement restrictions); and international travel-related measures. In this context, it does not include medical countermeasures such as drug administration or vaccination. PHSMs act in concert and a combination of measures is required to ensure adequate control. Measures should be implemented by the lowest administrative level for which situational assessment is possible and tailored to local settings and conditions. For more information, please refer to the Considerations for implementing and adjusting public health and social measures in the context of COVID-19.

# Adjusting PHSM
As the pandemic continues to evolve, PHSM should be regularly reviewed and adjusted according to the local epidemiology and its impact on the health system, including the community and the overall economy and society. This requires agile decision-making based on ongoing situational assessments at the most local administrative level possible in a coherent and coordinated manner with neighbouring areas at the sub-national and national levels. Such assessments should be based on available data and a risk/benefit approach considering the local epidemiology, the health system's capacity to respond and other contextual considerations (such as upcoming mass gathering events that may alter transmission or the health system's capacity). The choice of epidemiological indicators and their thresholds will depend on a country's data collection capacity, vaccination strategy and coverage, and the overall COVID-19 response strategy. Important dynamic indicators to be considered to determine the local situation are SARS-CoV-2 transmissibility, the seriousness of COVID-19, and the impact on the health system. Assessments based on these key indicators (transmissibility, seriousness of disease, and impact) need to be tailored to the local context. As a general principle, core PHSM (for example, mask use, physical distancing) should be maintained in priority groups, settings and situations, even during periods of low transmission. By combining data regarding the above-mentioned three key indicators, the following situation levels can be identified to describe the local situation.

# Situational level 0:
A situation with no known transmission of SARS-CoV-2 in the preceding 28 days. The health system and public health authorities are ready to respond, but there are no restrictions needed on daily activities.
Situational level 1: A situation with minimal transmission, morbidity and health system impact of SARS-CoV-2, with only basic ongoing PHSM needed.

# Situational level 2:
A situation where there is a moderate impact of COVID-19, although there may be a higher impact in specific subpopulations. Additional measures may be required to reduce transmission. However, disruptions to social and economic activities can still be limited, particularly if PHSM can be targeted strategically to more impacted settings.

# Situational level 3:
A situation with a significant impact on the health system and a risk of health services becoming overwhelmed, or unacceptably high morbidity and mortality, despite sufficient remaining health system capacity. A broader combination of PHSM may need to be put in place to limit transmission, manage morbidity, and avoid overwhelming the health system.
Situational level 4: An uncontrolled epidemic with very high morbidity/mortality and limited or no additional health system response capacity available, thus requiring extensive PHSM to avoid overwhelming of health services and substantial excess morbidity and mortality.

# Who are these recommendations intended for?
These guidelines are intended for policy-and decision-makers, public health professionals, and IPC professionals at national, sub-national, and facility levels.

# Mask use

# Mask use in the community
To assist national and global efforts to end the acute phase of the COVID-19 pandemic emergency worldwide, WHO published the 2022 COVID-19 Strategic Preparedness, Readiness and Response plan outlining strategic interventions to support these efforts. The first objective is to reduce and control the incidence of SARS-CoV-2 infections. This is essential to protect individuals from exposure, especially vulnerable individuals at risk of severe disease or occupational exposure to the virus, reduce the probability that future variants will arise, and reduce pressure on health systems. While the second objective is to prevent, diagnose and treat COVID-19 to reduce mortality, morbidity, and long-term sequelae. These actions may reduce pressure on the virus to evolve and the potential that future variants will emerge while simultaneously reducing the burden on the health system.
Masks are one component of a comprehensive package of prevention and control measures to limit the spread of SARS-CoV-2.
When aiming to reduce community transmission and mitigate the impact of COVID-19 outbreaks on health and social services, policies developed for mask use should be included as one element of a comprehensive package of preventive measures to reduce transmission (physical distancing, ventilation, mask use, hand hygiene, respiratory etiquette, and vaccination).
Considering the current stage of the pandemic, the GDG considered all available evidence on the effectiveness of mask-wearing the epidemiology of current VoC, transmission (data or patterns where available), the severity of disease and impact on health systems, vaccine efficacy, access, uptake, and potential immune evasion. The complementary strong and conditional recommendations on mask use in the community outline possible scenarios in which mask use may be of benefit.
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)

# Implementation consideration

# Practical Info

# Implementation considerations
The implementation and adjustment of policies on mask use should be based on available scientific data and a risk/benefit approach considering the local epidemiology, the health system's capacity to respond, and other contextual considerations (events that may alter community transmission or the health system's capacity to respond to the resurgence of cases). The local situation can be determined based on the above-mentioned criteria related to the transmissibility of SARS-CoV-2, the seriousness of the disease, and the impact of the virus.
The evidence available on mask use in the community setting is based on the use of medical masks. Fabric (non-medical) masks can be used when access to medical masks is limited. While filtering facepiece respirators have demonstrated a higher filtration level, there is limited evidence to suggest that filtering facepiece respirators should be used in community settings.
Exhalation valves on respirators and non-medical masks are discouraged as they do not allow for adequate source control from the wearer. Exhalation valves permit a bypass of the filtration layers when the wearer exhales, thus potentially allowing infectious particles to pass through.
Face shields are considered to provide a level of eye protection only and should not be considered as an equivalent to masks with respect to respiratory protection and/or source control. Current laboratory testing standards only assess face shields for their ability to provide eye protection from chemical splashes.

# Additional details
For additional information on the environmental impact of mask use (and other PPE), please see the WHO's Global analysis of health care waste in the context of COVID-19.

# Strong recommendation for, low to moderate certainty of evidence
Strong recommendation for WHO recommends the use of a mask for the prevention of SARS-CoV-2 transmission in the community in the following situations:
- when in crowded, enclosed, or poorly ventilated spaces 1 ;
- following a recent exposure to COVID-19 (according to the WHO definition 2 when sharing a space with others;
- when sharing a space with a person who displays signs or symptoms of COVID-19 3 or is COVID-19-positive;
- for individuals at high risk 4 of severe complications from COVID-19. 1 For example, a setting in which it is not possible to physically distance at least 1 metre. For the essential parameters concerning fabric (non-medical) and medical masks, see the following implementation consideration.

# Evidence To Decision
The utilization of masks in community settings is associated with a decreased risk of SARS-CoV-2 infections compared with no mask-wearing. Despite the low-to-moderate certainty of the evidence, GDG members agreed that WHO should issue recommendations as the net benefits of mask use by the public outweigh the potential harms. The situations outlined above have been identified by consensus as settings and conditions in which masks should always be utilized.
Available evidence includes two open-label RCTs and ten observational studies. A large (n=342,183) cluster RCT found a mask promotion intervention associated with decreased risk of symptomatic SARS-CoV-2 seroprevalence (adjusted prevalence ratio 0.91, 95% CI 0.82 to 1.00). An individually randomized RCT (n=6,024) found a recommendation to use masks associated with decreased risk of SARS-CoV-2 infection, though the difference was not statistically significant (odds ratio 0.82, 95% CI 0.54 to 1.23); this trial was not designed to evaluate effects of masks as source control. The RCTs had methodological limitations, including open-label design, attrition, incomplete outcome assessment, variable adherence, and differential recruitment. The RCTs were consistent and were not downgraded for imprecision (due to the very large total sample size  with a precise estimate from one of the trials). Only one trial evaluated a mask recommendation directly. The other evaluated a mask promotion intervention and did not evaluate mask use or a mask recommendation directly ; this resulted in suboptimal uptake of make use and would underestimate the effects of mask use. Therefore, the RCTs were not downgraded for indirectness (See Annex 2).
The observational studies were generally consistent with the RCTs, but had some imprecision, inconsistency and methodological limitations    . Although the estimates of the ten available observational studies were imprecise and had a degree of variability, in addition to other biases intrinsic to observational studies, overall, mask use was associated with a decreased risk of SARS-CoV-2 infection compared to no mask use    . Ecological studies identified an association between a reduced number of confirmed cases of COVID-19 and policies requiring the use of masks. No studies assessed the effectiveness of mask use in specific settings (for example, indoor, outdoor, or ventilation status). Overall, the certainty of the evidence (based primarily on the two RCTs, and supplemented by the ten observational studies) is assessed as low-to-moderate.

# Substantial net benefits of the recommended alternative

# Benefits and harms
Available evidence includes two open-label RCTs and ten observational studies. The cluster RCT explored the use of mask promotion while the other RCT presented an imprecise estimate and was not designed to assess the effectiveness of source control. The observational studies had some imprecision, inconsistency and methodological limitations. Therefore, the certainty of the evidence is reported as low-to-moderate.

# Certainty of the Evidence
Discussions with GDG members indicated a general preference towards favouring mask use in community settings, although the values and preferences of individuals may vary. Many members indicated that those at high risk of severe disease may find more value in the use of masks compared to other individuals.

# No substantial variability expected

# Values and preferences
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
In response to the shift in the epidemiology of COVID-19, GDG members reformulated the recommendations to no longer rely on the local transmission scenario of SARS-CoV-2. Given the sustained SARS-CoV-2 transmission globally, a majority of GDG members agreed that a situational approach to mask use is more appropriate than the previous transmission-based approach. GDG members indicated that the benefits of mask use outweigh the potential harms as masks are an effective mitigation tool, especially in crowded, enclosed, and poorly ventilated settings such as public transportation, busy storefronts, and crowded workplaces and educational centres. The GDG decided for this strong recommendation in conjunction with the conditional to ensure coverage across all situations where masking may be beneficial.
GDG members indicated that the global supply chain for mask manufacturing has improved and would not pose a severe obstacle to community masking. The cost of both medical masks and non-medical masks is relatively low and does not pose a substantial barrier for low-and middle-income countries. However, medical masks should not be reused and should be changed when wet or soiled, potentially requiring the use of multiple masks per day, leading to additional resource implications, such as cost, availability and access. Additionally, there are environmental impacts associated with disposable masks, such as additional waste and litter. Additional considerations are needed for proper disposal.

# Gaps in knowledge and research needs
Investigations on the benefits and harms of masks and their utilization in the community setting are ongoing and published work has identified this need for continued research. Well-conducted, observational studies and/or RCTs exploring the use of masks versus no masks in various settings (for example, indoor, outdoor, ventilation status) would further clarify outstanding questions concerning mask use in community settings. In addition, research investigating the use of masks (including the type of mask and transmission scenarios) in the context of the emerging variants of concern would provide powerful evidence for future recommendations. However, GDG members discussed the challenges associated with obtaining compelling evidence from a RCT on behavioural interventions. Furthermore, with the availability of SARS-CoV-2 immunization and increased natural immunity, further research will be needed to reinforce the impact of vaccination and, consequently, the effect that immunization status will have on mask utilization in community settings. Additional research and innovation is needed in the area of reuseable and recyclable medical masks that comply with existing standards.
No important issues with the recommended alternative
No issues were documented regarding inequities. Using masks as a preventative measure for SARS-CoV-2 infection may reduce the burden of infection, especially for those at high risk of severe disease. Studies did not examine equity issues, such as providing information on race, gender, or vulnerable populations. More studies addressing these aspects should be carried out to inform the decision-making process.
No important issues with the recommended alternative
Complex issues arise when examining the acceptability of mask use in communities. These include the type of mask recommended, personal preference, possible local economic and procurement constraints and the ecological impact (environmental impact and waste management) . Members indicated that those at high risk of severe sequelae might find more benefit in mask-wearing compared to other individuals. Furthermore, members of the general public may not deem mask use as an acceptable public health intervention and thus, demonstrate resistance towards masking policies. However, the evidence points to the benefits outweighing the harms. Variability exists in the published studies examining mask compliance.

# Important issues, or potential issues not investigated
Given the current availability of masks, community masking is likely feasible, despite the potential acceptability issues mentioned above.
Important issues, or potential issues not investigated
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)

# Implementation consideration

# Practical Info
Practical considerations for policy-makers:
The potential advantages of mask use by healthy people in the general public include:
- reduced spread of potentially infectious aerosols or droplets from exhaled breath, including from infected people before they develop symptoms ; - encouraging concurrent transmission prevention behaviours such as washing hands and not touching the eyes, nose and mouth  ; and - preventing transmission of other respiratory illnesses such as tuberculosis and influenza and reducing the burden of these diseases during the pandemic.
The potential disadvantages of mask use by healthy people in the general public include:
- Adverse events include: headache and/or breathing difficulties, depending on the type of mask used ; potential physiological changes ; development of facial skin lesions, irritant dermatitis or worsening acne when used frequently for long hours [

# Conditional recommendation for, low to moderate certainty of evidence

# Conditional recommendation for
In situations not addressed by the strong recommendation, WHO suggests a risk-based approach to inform the decision to use a mask for the prevention of SARS-CoV-2 transmission in the community.
Factors that favour mask use:
- COVID-19 epidemiological trends at the community level indicating high or rising transmission or hospitalizations;
- low coverage of COVID-19 vaccination;
- low levels of population immunity to SARS-CoV-2;
- a greater degree of crowding 1 poorer indoor ventilation, and/or the presence of individual risk factors 2.
respiratory or breathing problems; those who have had facial trauma or recent oral maxillofacial surgery; and those living in hot and humid environments . For the essential parameters concerning fabric (non-medical) and medical masks, see the following implementation consideration.

# Additional details

# Evidence To Decision
The utilization of masks in community settings is associated with a decreased risk of SARS-CoV-2 infections compared with no mask-wearing. Despite the low-to-moderate certainty of the evidence, GDG members agreed that WHO should issue recommendations as the net benefits of mask use by the public outweigh the potential harms. The situations outlined above have been identified by consensus as settings and conditions in which masks should always be utilized.
Available evidence includes two open-label RCTs and ten observational studies. A large (n=342,183) cluster RCT found a mask promotion intervention associated with decreased risk of symptomatic SARS-CoV-2 seroprevalence (adjusted prevalence ratio 0.91, 95% CI 0.82 to 1.00). An individually randomized RCT (n=6,024) found a recommendation to use masks associated with decreased risk of SARS-CoV-2 infection, though the difference was not statistically significant (odds ratio 0.82, 95% CI 0.54 to 1.23); this trial was not designed to evaluate effects of masks as source control. The RCTs had methodological limitations, including open-label design, attrition, incomplete outcome assessment, variable adherence, and differential recruitment. The RCTs were consistent and were not downgraded for imprecision (due to the very large total sample size  with a precise estimate from one of the trials). Only one trial evaluated a mask recommendation directly. The other evaluated a mask promotion intervention and did not evaluate mask use or a mask recommendation directly ; this resulted in suboptimal uptake of make use and would underestimate the effects of mask use. Therefore, the RCTs were not downgraded for indirectness (See Annex 2).
The observational studies were generally consistent with the RCTs, but had some imprecision, inconsistency and methodological limitations  . Although the estimates of the ten available observational studies were imprecise and had a degree of variability, in addition to other biases intrinsic to observational studies, overall, mask use was associated with a decreased risk of SARS-CoV-2 infection compared to no mask use  . Ecological studies identified an association between a reduced number of confirmed cases of COVID-19 and policies requiring the use of masks. No studies assessed the effectiveness of mask use in specific settings (for example, indoor, outdoor, or ventilation status). Overall, the certainty of the evidence (based primarily on the two RCTs, and supplemented by the ten observational studies) is assessed as low-to-moderate.

# Substantial net benefits of the recommended alternative

# Benefits and harms
Available evidence includes two open-label RCTs and ten observational studies. The cluster RCT explored the use of mask promotion while the other RCT presented an imprecise estimate and was not designed to assess the effectiveness of source control. The observational studies had some imprecision, inconsistency and methodological limitations. Therefore, the certainty of the evidence is reported as low-to-moderate.

# Certainty of the Evidence
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
GDG members decided for this conditional recommendation in conjunction with the aforementioned strong recommendation. In addition to situations where masks are strongly advised (when in crowded, enclosed, or poorly ventilated spaces; following recent exposure to COVID-19; when sharing a space with a person who displays symptoms of COVID-19 or is COVID-19-positive; and for individuals at high risk of severe complications from COVID-19), there are additional times where wearing a mask may be Discussions with GDG members indicated a general preference towards favouring mask use in community settings, although the values and preferences of individuals may vary. Many members indicated that those at high risk of severe disease might perceive the benefits of mask use to be greater compared to other individuals.

# Substantial variability is expected or uncertain

# Values and preferences
Many GDG members noted that the global supply chain for mask manufacturing has improved and would not pose a severe obstacle to community masking. The cost of both medical and non-medical (fabric) masks is relatively low and does not pose a substantial barrier for low-and middle-income countries. However, medical masks should not be reused and changed when wet or soiled, potentially requiring the use of multiple masks per day, leading to additional resource implications, such as cost, availability and access. Additionally, there are environmental impacts associated with disposable masks, such as additional waste and litter. Additional considerations are needed for proper disposal.

# Gaps in knowledge and research needs
Investigations on the utilization of masks in the community setting are ongoing, but published work has identified this need for continued research. Observational studies and/or RCTs designed and conducted with rigorous scientific methods exploring the use of masks versus no masks in various settings (for example, indoor, outdoor, ventilation status) would further clarify outstanding questions concerning mask use in community settings. In addition, research investigating the use of masks (including the type of mask and transmission scenarios) in the context of VoC would provide powerful evidence for future recommendations. However, GDG members discussed the challenges associated with obtaining compelling evidence from an RCT on behavioural interventions. Furthermore, with the availability of SARS-CoV-2 immunization and increases in natural immunity, further research will be needed to reinforce the impact of vaccination and; consequently, the effect immunization status will have on mask utilization in community settings. Additional research and innovation is needed in the area of reusable and recyclable medical masks that comply with existing standards.
No important issues with the recommended alternative
No important issues were documented regarding inequities, although this arena would benefit from further investigation.
No important issues with the recommended alternative
Complex issues arise when examining the acceptability of mask use in communities. These include the type of mask recommended, personal preference and ecological impact (environmental impact and waste management) .
Members indicated that those at high risk of severe sequelae might find more benefit in mask-wearing compared to other individuals. Furthermore, it has been indicated that members of the general public may not deem mask use as an acceptable public health intervention and, thus, demonstrate resistance towards masking policies. However, the evidence points to the benefits outweighing the harms. Variability exists in the published studies examining mask compliance.
Important issues, or potential issues not investigated beneficial. Although there are limited data on the effectiveness of a risk-based approach and implementation may be a challenge, the benefits of mask wearing outweigh the risks.
Members indicated that masks should be considered when there are high-to-moderate levels of community transmission (situational levels 2 to 4) and low-to-moderate vaccination coverage while taking into consideration individual risk factors in addition to personal values and preferences based on the perception of the risk and the potential harm and consequences of being affected by COVID-19.

# Implementation consideration

# Mask management
For any type of mask, appropriate use, storage, cleaning or disposal are essential to ensure that they are as effective as possible and to avoid any increased risk of transmission. Adherence to correct mask management practices varies, reinforcing the need for appropriate messaging. WHO provides the following guidance on the correct use of masks:
- Wash hands thoroughly before putting on the mask.
- Inspect the mask for tears or holes, and do not use a damaged mask.
- Place the mask carefully, ensuring it covers the mouth and nose, adjust to the nose bridge and tie it securely to minimize any gaps between the face and the mask. If using ear loops, ensure these do not cross over as this widens the gap between the face and the mask. - Avoid touching the mask while wearing it. If the mask is accidently touched, wash hands thoroughly.
- Remove the mask using the appropriate technique. Do not touch the front of the mask; rather, untie it from behind.
- Replace the mask as soon as it becomes damp with a new, clean and dry mask.
- Either discard the mask or place it in a clean plastic resealable bag where it is kept until it can be washed and cleaned. Do not store the mask around the arm or wrist or pull it down to rest around the chin or neck. - Wash hands immediately after discarding a mask.
- Do not reuse single-use masks.
- Discard single-use masks after each use and properly dispose of them immediately upon removal.
- Do not remove the mask to speak.
- Do not share your mask with others.
- Wash fabric masks in soap or detergent and preferably hot water (at least 60 Centigrade/140 Fahrenheit) at least once a day. If it is not possible to wash the masks in hot water, then wash the mask in soap/detergent and room-temperature water, followed by boiling the mask for 1 minute. - A mask should be changed to a clean mask at least once daily.