Infection prevention and control in the context of coronavirus disease 2019 : a living guideline consolidates the infection prevention and control (IPC) technical guidance developed and published during the COVID-19 pandemic into evidenceinformed recommendations for IPC. Part 1 presents IPC recommendations in the context of health care settings, while Part 2 presents recommendations for community settings. The methodology section describes the methodological approach used to develop the guideline, including a glossary of terms and abbreviations. Annexes are included at the end of the document with evidence tables, systematic review details and PICO (populations, interventions, comparisons, and outcome) questions.
The living guideline is written, disseminated and updated on an online platform (MAGICapp). It has a user-friendly format and easy-tonavigate structure that accommodates dynamically updated evidence and recommendations. This structure focuses on what is new while keeping existing recommendations updated within the guideline.
This living guideline considers the current and evolving epidemiological trends for COVID-19 and the emergence of new variants of concern (VOCs) and factors such as population immunity, availability and uptake of vaccines and other contextual factors of the COVID-19 pandemic.
The target audiences of these guidelines are policy-and decision-makers; public health professionals; IPC professionals and focal points for occupational health and safety of health workers at the national, subnational and facility levels; health care facility administrators and managers; and other health and care workers.

# Updated section
This version of the guidelines (version 5.0), includes the following seven revised statements for the prevention, identification and management of SARS-CoV-2 infections among health and care workers:
- a good practice statement on national and subnational testing strategies 2. a good practice statement on passive syndromic surveillance of health and care workers 3. a good practice statement on prioritizing health and care workers for SARS-CoV-2 testing 4. a good practice statement on protocols for reporting and managing health and care worker exposures 5. a good practice statement to limit in-person work of health and care workers with active SARS-CoV-2 infections 6. a statement on high-risk exposures and quarantine 7. a conditional recommendation on the duration of isolation for health and care workers.

# Understanding the updated section
The updated section of this guideline focuses on the prevention, identification, and management of SARS-CoV-2 infections among health and care workers in health settings.
Prevention of infections in the health care setting includes a multi-pronged and multi-factorial approach that includes IPC and occupational health and safety (OHS) measures and adherence to Public Health and Social Measures (PHSM) in the community by the health workforce. See the chapter on "What is an IPC programme" and the chapter on "Introduction to public health and social measures" for additional information.
The underlying infection prevention and control strategy of this section is the notion that early identification of symptomatic cases, testing and quarantining/isolating health and care workers decreases the risk of nosocomial infection. While the systematic review of evidence used to support these recommendations did not result in an adequate yield of strong evidence, the statements found in this updated chapter were guided by expert advice, based in traditional IPC practices and supplemented by other WHO guidance/ guidelines.

# Updates and prior versions
Version 1.0 of the COVID-19 infection prevention and control living guideline: mask use in community settings published in December 2021 provided new guidelines on mask use in community settings. This guideline superseded existing advice in Mask use in the context of COVID-19 issued in December 2020. Version 4.0 of the living guideline is the most recent update on guidelines for mask use in the community. Version 2.0 of the COVID-19 living guideline jointly developed by the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) was published in March 2022. This version contained updated guidelines on mask use in children. Advice on the use of masks for children in the context of COVID-19 was first published in August 2020 as an annex to the document Mask use in the context of COVID-19 . Version 2.0 of the living guideline superseded any previous advice on the use of masks for children in the

# Active screening
This involves actively looking for signs and symptoms either by asking the health or care worker questions regarding their symptoms through a questionnaire, electronic format or verbally. It involves actively asking or assessing health workers (temperature checks, testing) health status to identify signs and symptoms of infection. This mode of screening could be considered if human resources and logistics permit when the health care facility finds itself in an active outbreak or when there is heightened transmission in the health care facility or in the community where the health facility is located. Health workers should be screened after any potential exposure risks before or on arrival for their shift -either through questionnaires (online or in-person) or through testing (rapid-antigen tests or PCR). The signs or symptoms to be monitored should include fever, cough, general weakness, fatigue, headache, myalgia, sore throat, coryza, dyspnoea, nausea, diarrhoea and anorexia).

# Adequately ventilated patient room or area
Adequate ventilation in health facilities can be assessed where a natural or mechanical ventilation system is available. The ventilation rate should be 6-12 air changes per hour (e.g. equivalent to 40-80 L/s/patient for a 4x2x3 m3 room) and ideally 12 air changes per hour for new constructions, with a recommended negative pressure differential of 2.5Pa (0.01-inch water gauge) to ensure that air flows from the corridor into patient rooms.

# Aerosol generating procedures (AGP)
Aerosol-generating procedures (AGP) are defined as any medical procedures that can induce the production of aerosols of various sizes (e.g. tracheal intubation, non-invasive ventilation(e.g. bilevel positive airway pressure, continuous positive airway pressure), tracheostomy, cardiopulmonary resuscitation, manual ventilation before intubation, bronchoscopy, dental procedures, tracheotomy, cardiopulmonary resuscitation, manual ventilation before intubation, sputum induction by using nebulized hypertonic saline, dentistry and autopsy procedures. In oral health care, the following are considered AGPs: all clinical procedures that use spray generating equipment such as three-way air/water spray, dental cleaning with ultrasonic scaler and polishing; periodontal treatment with ultrasonic scaler; any kind of dental preparation with high-or low-speed hand p ieces; direct and indirect restoration and polishing; definitive cementation of crown or bridge; mechanical context of COVID-19. Version 3.0 of the COVID-19 living guideline published in April 2022  provided new recommendations on mask use in healthcare settings. This updated guideline superseded previous advice on mask use in the health care setting in the context of COVID-19 .
Version 4.0 of the COVID-19 living guideline published in January 2023  provided updated guidelines on mask use in the community. This guideline superseded the guideline found in version 1.0 and all existing interim guidance on mask use in the community . Version 5.0 of the living guideline, supersedes the previous guidance on the Prevention, identification and management of health and care worker infection in the context of COVID-19 issued in October 2020.

# Guideline development
This guideline was developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) processes and Evidence to Decision framework  and in accordance with WHO norms and standards for guideline development. The composition of the Guidelines Development Group (GDG) includes experts in IPC, epidemiology, infectious diseases, paediatrics, water, sanitation and hygiene, engineering, aerobiology; and healthcare providers. The groups were balanced according to geographical and gender representation. Different GDGs were convened to address specific settings or populations (see authorship, contributors, and acknowledgments section). A methodologist with expertise in guideline development assisted the GDG in formulating the recommendations and statements. While the GDG assumes the perspective of an individual patient in making recommendations, it also considers resource implications, acceptability, feasibility, and equity. The WHO Quality Assurance of Norms and Standards department helped to identify published rapid systematic reviews for the review process. Where required, WHO staff or commissioned external review teams conducted systematic reviews to address specific questions. Due to the rapidly evolving nature of the pandemic, preprints were included in the evidence synthesis. Additional details are described in the methodology section.

# Updates and access
This guideline and its previous versions are available through the WHO website and MAGICapp (online and PDF outputs for readers with limited internet access).
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO) endodontic treatment; surgical tooth extraction and implant placement.

# Airborne transmission
Airborne transmission refers to the spread of an infectious agent caused by the dissemination of droplet nuclei that remain infectious when suspended in air over long distances and time. Airborne transmission can be further categorized into obligate or preferential airborne transmission.
- Obligate airborne transmission refers to pathogens that are transmitted only by deposition of droplet nuclei under natural conditions (e.g. pulmonary tuberculosis). - Preferential airborne transmission refers to pathogens that can initiate infection by multiple routes but are predominantly transmitted by droplet nuclei (e.g. measles and chickenpox). - Opportunistic airborne transmission refers to agents that naturally cause disease through other routes, but under special circumstances may be transmitted via fine particle aerosols.
A child A child refers to any person under the age of 18 years.

# Contact transmission
Contact transmission is the spread of an infectious agent caused by physical contact of a susceptible host with people or objects.
- Direct contact transmission involves both a direct body-surface-to-body-surface contact and physical transfer of microorganisms between an infected or colonized person and a susceptible host. - Indirect contact transmission involves contact of a susceptible host with a contaminated intermediate object (e.g. contaminated hands) that carries and transfers the microorganisms.

# Droplet transmission
Droplet transmission is the spread of an infectious agent caused by the dissemination of droplets. Droplets are primarily generated from an infected (source) person during coughing, sneezing, and talking. Transmission occurs when these droplets that contain microorganisms are propelled (usually 99%) comprises large droplets that travel short distances (< 1 m) and do not remain suspended in the air. Thus, special air handling and ventilation are not required to prevent droplet transmission.

# Hand hygiene
Hand hygiene is general term referring to any action of hand cleansing. Antiseptic hand rubbing refers to applying an antiseptic hand rub to reduce or inhibit the growth of microorganisms without the need for an exogenous source of water and requiring no rinsing or drying with towels or other devices. Handwashing refers to washing hands with plain or antimicrobial soap and water.

# Health care facility
Health care facilities include primary, secondary, tertiary care levels, outpatient care, and long-term care facilities.

# Health workers/ health and care workers
Health and care workers are all people from in the community to hospitals, primarily engaged in actions with the primary intent of enhancing health. This includes health service
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
providers, such as doctors, nursing and midwifery professionals, public health professionals, technicians (laboratory, health, medical, and non-medical), personal care workers, healers and practitioners of traditional medicine. It also includes health management and support workers, such as cleaners, drivers, hospital administrators, district health managers, social workers, and other occupational groups in health-related activities. This group includes those who work in acute care facilities and long-term care, public health, community-based care and other occupations in the health and social care sectors.
Health and care workers may provide direct personal care services in the home, in health care and residential settings, assisting with routine tasks of daily life and performing a variety of other tasks of a simple and routine nature.

# High-risk exposures
High-risk exposures in the health care facility occur when health and care workers provide direct care to a patient with an infectious disease without any, or with inappropriate PPE, or experience a breach in PPE integrity, or a lapse in IPC measures (i.e., hand hygiene not performed as per the WHO 5 moments, lack of cleaning and disinfection of surface/ environment); or when a health and care worker is present during an AGP with inappropriate PPE, breach in PPE integrity, or other IPC measures not followed; or exposure to splash or spray of body fluids/blood and/or a puncture/sharp injury  (adapted).

# Filtering facepiece respirators (FFR or respirators)
Filtering facepiece respirators (FFR or respirators) offer a balance of filtration, breathability and fit. Whereas medical masks filter 3-micrometre droplets, "N95" and "FFP2" rated FFRs must filter a more challenging 0.075-micrometre particles or particulates and do so across the entire surface of the respirator as a result of the fitted design. European "FFP2" FFRs, according to EN 149 standard, filter at least 94% Sodium Chloride (NaCl) salt particles and paraffin oil droplets. The United States of America "N95" FFRs, according to National Institute for Occupational Safety and Health (NIOSH) NIOSH 42 CFR Part 84, filter at least 95% NaCl salt particles. Certified FFRs must ensure unhindered breathing by meeting inhalation and exhalation breathing resistances below the maximum thresholds. Another important difference between FFRs and other masks is how filtration is tested. Medical mask filtration is assessed by testing filtration over a cross-section of the masks. In contrast, FFRs are tested for filtration across the entire surface. Most importantly, "FFP2" FFRs are fittested on a sample of human participants and the FFRs are measured for leaks as part of product certification. Similarly, for "N95" FFRs, individual workers are fit tested for specific FFRs at the workplace and typically on an annual basis. Therefore, in both cases, by ensuring the outer edges of the FFR seal around the wearer's face, the FFRs filtration is closer to the actual filtration of inhaled air. Other FFR performance requirements include being within specified parameters for maximum CO2 build-up.

# Medical masks
Medical masks are surgical or procedure masks that are flat or pleated and are affixed to the head with straps around the ears, the head or both. Their performance standards are tested according to a set of standardized test methods (American Society for Testing Materials (ASTM) ASTM F2100, EN 14683, or equivalent) that aim to balance high filtration, adequate breathability and, optionally, fluid penetration resistance.

# Non-medical masks
Non-medical masks are a type of facial covering of the mouth and nose of the wearer used to mitigate the spread of respiratory infections but do not meet the performance standards of 'medical' or 'surgical' masks. Their primary purpose is for source control and to provide a degree of particulate filtration to reduce the amount of inhaled particulate matter. Essential parameters for the performance and safety of non-medical masks have been advocated during the COVID-19 Public Health Emergency of International Concern (PHEIC) through several existing international guidelines and one international standard for non-medical masks (ASTM F3502-21)  . Non-medical masks that are self-made or commercially produced and do not meet guideline supported essential parameters are permitted in areas that have not mandated minimum performance requirements for nonmedical masks prior to sale and for use by the general public.

# Occupational health and safety
A multidisciplinary area of work aiming at the promotion and maintenance of the highest degree of physical, mental and social well-being of workers in all occupations; the prevention among workers of effects on health from their working conditions; the protection of workers in their employment from risks resulting from factors adverse to health; and the placing and maintenance of the workers in an occupational environment adapted to their physiological and psychological capabilities.
Passive screening (self-reporting)
Passive (self-reporting), in contrast to active surveillance, allows health and care workers to self-report symptoms of illness to appropriate occupational health and safety or other designated officer in the facility before and during or after their shift. This may be the most suitable option in countries where human, financial and technical resources are limited. It is the most common type of surveillance in humanitarian emergencies.

# Standard precautions
Standard precautions aim to protect health and care workers and patients by reducing the risk of transmission of microorganisms from both recognized and unrecognized sources. They are the minimum standard of infection prevention and control (IPC) practices that should be used by all healthcare workers, during the care of all patients, at all times, in all settings. When applied consistently, standard precautions can prevent the transmission of microorganisms between patients, health and care workers and the environment. Key elements of standard precautions include: 1) risk assessment, 2) hand hygiene, 3) respiratory hygiene and cough etiquette, 4) patient placement, 5) personal protective equipment, 6) aseptic technique, 7) safe injections and sharps injury prevention, 8) environmental cleaning, 9) handling of laundry and linen, 10) waste management, and 11) decontamination and reprocessing of reusable patient care items and equipment.

# Syndromic screening
Syndromic screening is the near real-time collection, analysis, interpretation and dissemination of health-related data to enable the early identification of the impact (or absence of impact) of potential health threats that may require public health action .

# Universal masking
Universal masking is the requirement for all persons (staff, patients, visitors, service providers and others) in health facilities to wear a mask at all times except when eating or drinking.

# Targeted continuous medical mask use
Targeted continuous medical mask use is the practice of wearing a medical mask by all health workers and caregivers working in clinical areas during all routine activities throughout the entire shift.

# Transmission-based precautions
Transmission-based precautions are used in addition to standard precautions for patients with known or suspected infection or colonization with transmissible and/or epidemiologically significant pathogens. The type of transmission-based precautions assigned to a patient depends on the transmission route of the microorganism: contact, droplet or airborne. Transmission-based precautions must be started as soon as a patient presents with symptoms (e.g. fever, new cough, vomiting, diarrhoea). There is no need to wait for test results.

# Methodology Guideline Development Groups (GDG) and External Review Groups
The GDG was convened to review the available evidence and determine IPC recommendations, good practice statements (GPS) and implementation considerations included in this document. The GDG consisted of individuals with broad expertise spanning multiple specialties, across all WHO regions, and was gender balanced. Consensus was sought for recommendations and GPS. When consensus was not achieved, approval of a recommendation or GPS required a majority ( 70%) of the GDG voting members. Standard WHO procedures for collection, evaluating and acting based on declarations of interest (DOI) were followed .
External review group members were also identified for specific technical areas and provided an additional review of the guidelines. External review groups do not change the recommendations made by the GDG; however, any major concerns are brought back to the GDG for additional discussion. For more information on authorship, contributions, and DOI, please refer to the acknowledgement section.

# Evidence synthesis and assessment
As noted in the Executive Summary, with support from the WHO Quality Assurance of Norms and Standards department, rapid systematic reviews of published literature were identified for review. Due to the time lag for peer-reviewed publication of relevant studies in the context of a dynamic pandemic, preprints were included in some evidence syntheses.
The literature for each identified topic was assessed using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) to determine the certainty of the evidence (Table 1) based on the presence of risk of bias/study limitations, inconsistency, imprecision, indirectness and publication/reporting biases.
The Group is very confident in the estimate of effect and considers that further research is very unlikely to change this confidence.
The Group has moderate confidence in the estimate of effect and considers that further research is likely to have an important impact on that confidence and may change the estimate.
The Group has low confidence in the estimate of effect and considers that further research is very likely to have an important impact on that confidence and is likely to change the estimate.

# Very low
The Group is very uncertain about the estimate of the effect.
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
Evidence reviews for chapters on mask use in health care settings and the community. Systematic reviews were commissioned to external groups (clinical effectiveness of mask use in health care and community settings) and conducted by WHO staff (ecological studies on mask effectiveness) to assess the evidence on mask use in various settings. Reviews were conducted using pre-defined protocols with pre-specified key questions and scope using the PICO (populations, interventions, comparisons, and outcomes) framework. Evidence was identified using systematic searches on electronic database and the searches were regularly updated to identify emerging evidence.
Evidence from randomized controlled trials (RCT) remains limited. Therefore, the reviews include non-randomized studies, cohort, casecontrol and ecological studies. The systematic reviews are presented in GDG meetings and are supplemented by other (nonsystematically reviewed) data presented by WHO staff, Member States or partner organizations. Supplemental data-informed considerations regarding contextual factors on mask recommendations, mask filtration properties and technical specifications on ventilation, including mask values/preferences, acceptability and feasibility in the context of the changing epidemiology of COVID-19.
Evidence review for the section on management, identification and prevention of infections in health and care workers A systematic review was conducted by the WHO Quality Assurance of Norms and Standards department to assess the latest evidence on the prevention, identification and testing and management of infected health and care workers. The search strategy for this review was designed in conjunction with the IPC team and conducted by the librarian and members of the IPC team. The PICOs were developed in conjunction with the GDG chairs, methodologists and secretariat to examine research not yet evaluated to provide the basis for an evidence-based decision. The WHO COVID-19-database, which includes results from several databases, was searched from January 2020 up to June 2022. Full details can be found in Annex 4.
The PICO questions included in this systematic review were: Evidence from randomized control trials (RCT) has been limited during the pandemic. Therefore, the reviews included mostly nonrandomized studies, cohort, case-control, and ecological studies. The systematic reviews were presented in GDG meetings and were supplemented by other (non-systematically reviewed) data presented by WHO staff. Such presentations informed considerations regarding contextual factors on testing health and care workers, their recommended isolation period, when to return to work after an infection and under which conditions. The GDG also received regular updates on SARS-CoV-2 epidemiology and transmission from the WHO epidemiology team. In addition, the WHO Clinical Management team for COVID-19 presented a systematic review on the period of infectiousness, which influenced the GDG's recommendations on the duration of isolation needed for a positive COVID-19 case. Some members of the IPC GDG participated in the development of this recommendation by the Clinical Management GDG, and the recommendation was also adopted for health and care workers.

# Process for developing recommendations
Once the certainty of the evidence was determined, the GDG, with the guidance of the methodologist, determine if a recommendation (strong or conditional) or a GPS was warranted. GRADE evidence profiles contain an assessment of the certainty of the evidence and a summary of findings for each critical outcome and each key question. The GDG used these summaries as the basis for discussions and formulation of recommendations.
The Evidence to Decision (EtD) framework was used by the GDG to support the formulation of the recommendation or GPS. Core domains in the EtD framework are the balance of benefits and harms and the quality of the evidence, although other EtD domains (values/preferences, acceptability, feasibility, costs, and equity) also informed the recommendations (Table 2). The EtD domain assessments (including values/preferences and equity) were based on the collective input and experience of the GDG, supplemented by key studies suggested by GDG members. Additional systematic reviews were not commissioned, and formal surveys outside of the GDG were not conducted.
The GDG graded recommendations as strong or conditional. Strong recommendations are applicable to all or nearly all persons/ situations and are indicated when benefits clearly outweigh harms with at least moderate certainty. Other factors that support strong recommendations are the non-sensitivity of the recommendation to variability in preferences/values regarding outcomes, wide feasibility and acceptability, cost savings or cost-effectiveness and likely positive impacts on improving equity. When certainty is low or very low, strong recommendations require a strong rationale for potential net benefit despite uncertainty in the evidence and strong supporting considerations (e.g. low cost, high feasibility, high acceptability and/or promotion of equity) from the other EtD domains. Conditional recommendations are applicable to most persons/situations, although it may be appropriate to not follow the recommendation in certain circumstances. Conditional recommendations are indicated when the balance of benefits to harms is close; when there is low certainty about benefits or harms; when decisions are preference-sensitive; or when there are concerns about feasibility, acceptability costs or impact on equity.
A GPS may be considered if the benefits of the recommended intervention are obvious and the actual certainty of benefits is high despite low or very low certainty evidence. GPS characteristically represents situations in which a large and compelling chain of indirect evidence strongly supports the net benefit of the recommended action. GPS are appropriate when the recommended statements are obvious best practices. GPS are not "GRADEd" statements. The GRADE tables used in this living guideline can be found in the Annex section of this living guidance.
For each recommendation or GPS, the GDG considered whether there were key considerations important for implementing the recommendation. "Implementation considerations" describe such considerations and include the circumstances under which conditional recommendations apply; technical considerations; and other factors relevant for patients, clinicians and policymakers implementing the recommendation or GPS.
The EtD framework for mask use in children was informed by five consultation sessions conducted by the United Nations Children's Fund (UNICEF) with members of the International Paediatric Association (IPA), and members from different geographical regions, in multiple languages, regarding paediatric health professionals' field experiences (including acceptability and feasibility) with the implementation of previous WHO guidance on masks. For other recommendations on mask use in health and care workers, the EtD domains were informed by presentations from invited stakeholders from different countries regarding acceptability and feasibility and by a presentation regarding mask availability and costs globally. The GDG also received regular updates on SARS-CoV-2 epidemiology and transmission from the WHO epidemiology team.
The GDG assessed whether statements constituted as GRADE'd recommendations or good practice statements. Due to the lack of strong evidence for health and care workers, the GDG concluded that most statements were good practice statements, considering wide feasibility and acceptability, cost savings or cost-effectiveness of the statements.

# Increased equity Decreased equity or effect on equity variable
Good practice statements and implementation considerations GPS are suitable when benefits are large and harm very small; the certainty of benefits and harms are great; the values and preferences are clear; the intervention is cost saving; and the intervention is clearly acceptable, feasible, and promotes equity. GPS characteristically represent situations in which a large and compelling body of indirect evidence, made up of linked evidence including several indirect comparisons, strongly supports the net benefit of the recommended action. GPS are generally issued for various reasons -including the process, priorities, timeline, resources or nature of the evidence being assessed -but they are rooted in the fact that answers are obvious. GPS are not "GRADEd" statements.
On many occasions, the GDG elects for a GPS instead of a strong or conditional recommendation. These GPS are part of an overall evidence-based process, and often a systematic review was commissioned to determine whether direct evidence was available. Instead, consistent with the methodology for developing GPS, an assessment by the GDG judged that the indirect evidence provided high certainty of benefit despite the insufficient evidence/very low-quality evidence to qualify it as a recommendation.
Implementation considerations are critical elements that facilitate the appropriate use of recommendations and GPS but are not assessed using the GRADE methodology. They may be actionable and relevant to implementing one of the intervention options and may include information to enhance implementation.
Readership cues for statements Table 3 presents the readership cues used for the statements in this living guideline. The green checkmark and red X symbols reflect statements that are developed using the GRADE evidence assessment methodology and the use of the evidence-to-decision framework to inform a recommendation or a GPS. The grey bar refers to implementation considerations that support statements through practical advice and are the product of expert consensus.

# Table 3. Readership cues used for statements in the living guideline
The GREEN checkmark symbol denotes a recommendation or a good practice statement in favour of an intervention.
The RED X denotes a recommendation or good practice statement against an intervention.
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
The GREY bar denotes an implementation consideration supporting the practical implementation of the statement.

# Periodicity of the guideline revision and updates
This guideline is formulated as a "living" guideline, meaning that revisions and updates will occur on an ongoing basis, based on the availability of new evidence. To inform the need for guideline revisions or updates, ongoing reviews are being conducted by WHO staff, as well as the externally commissioned living systematic review to identify emerging evidence on health and care worker infections and the use of masks in the context of the COVID-19 pandemic. New evidence identified in these reviews that could result in revised or new recommendations will trigger reconsideration of the evidence by the GDG. Other factors that may inform the need to update the guideline include changes in transmission intensity, circulation of new variants of concern, and health systems' capacity to respond to new epidemiological scenarios.

# What is an IPC programme?
What is an Infection Prevention and Control Programme? Infection prevention and control (IPC) is a practical, evidence-informed approach to preventing patients and health workers from being harmed by avoidable infections. Healthcare-associated infections (HAI) are among the most common adverse events in care delivery and a major public health problem impacting morbidity, mortality and quality of life. On average, 7% of patients in developed and 15% in developing countries will acquire at least one HAI. These infections also present a significant economic burden on society. A large percentage are preventable through effective IPC measures.

# Establishing an infection prevention and control programme at national and acute health care facility levels
The WHO Guidelines on core components of infection prevention and control programmes at national and acute health care facility levels  are the foundation of WHO strategies to prevent current and future threats from infection and antimicrobial resistance in health care. The core components constitute a framework of recommendations and good practices statements distributed into eight areas: 1) infection prevention and control programmes, 2) national and facility-level infection prevention and control guidelines, 3) IPC education and training, 4) health care-associated infections surveillance, 5): multimodal strategies for implementing infection prevention and control activities, 6) monitoring and evaluation and feedback, 7) workload, staffing and bed occupancy at the facility level and, 8) built environment, materials and equipment for IPC at the facility level. Ensuring adequate clinical staffing levels is recommended as a core component to prevent the transmission of HAI and multidrug-resistant organisms (MDROs); limit human-tohuman transmission; reduce secondary infections; and prevent transmission through amplification and super-spreading events.
Implementation of an IPC programme requires a stepwise approach to achieve its full potential. Minimum requirements as identified by WHO support the strengthening of IPC in countries where IPC is limited or nonexistent. In this regard, a facility-level IPC programme with a dedicated and trained IPC team, or at minimum, an IPC focal point, should be in place and supported by national-level and facility-level senior management. Achieving the IPC minimum requirements (and more robust and comprehensive IPC programmes in all countries) is essential to being able to control the COVID-19 pandemic, other emerging and re-emerging pathogens, and multidrug-resistant organisms (MDROs). Finally, WHO has also developed guidance on the core competencies  required for infection prevention and control professional staff, which can be used for developing curricula for IPC specialists.

# Environmental cleaning
The most up-to-date technical guidance for Cleaning and disinfection of environmental surfaces in the context of COVID-19: interim guidance was published on 15 May 2020. This guidance is under review and is pending integration into Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline.

# Home care for patients
The most up-to-date guidance for Homecare for patients with suspected or confirmed COVID-19 and management of their contacts: interim guidance was published 12 August 2020. This guidance is under review and is pending integration into Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline.

# IPC when COVID-19 is suspected or confirmed
The most up-to-date technical guidance for Infection prevention and control during health care when coronavirus disease (COVID-19) is suspected or confirmed: interim guidance was published 12 July 2021. This guidance is under review and is pending integration into Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline.
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)

# Part 1: Health care settings
The document Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline brings together IPC technical guidance developed and published since the beginning of the COVID-19 pandemic. This consolidated document aims to provide users with the latest evidence-informed recommendations, through the MAGICapp platform, as a way to easily navigate guidelines in the dynamic context of COVID-19. Many parts of the technical guidance related to Part 1: Health care settings are currently under review. Links to the most recent publication of the technical guidance are available in the sections that follow. Updated guidelines on health care settings will be available in this living guideline in the near future.

# IPC principles and procedures for COVID-19 vaccination activities
The most up-to-date technical guidance for Aide-memoire: infection prevention and control (IPC) principles and procedures for COVID-19 vaccination activities was published 15 January 2021. This guidance is under review and is pending integration into Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline.

# Long term care facilities
The most up-to-date guidance for Infection prevention and control guidance for long-term care facilities in the context of COVID-19: interim guidance was published 21 March 2020. This guidance is under review and is pending integration into Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline.

# Mask use Background
The WHO continuously reviews available data on SARS-CoV-2 variants of concern. For this version, the global epidemiological situation of the COVID-19 pandemic as of 21 January 2022 -at a time when the Omicron VOC had been identified in 171 countries across all six WHO Regions and was rapidly replacing Delta worldwide -was considered .
Omicron has a substantial growth advantage, higher secondary attack rates and a higher observed reproduction number than Delta.
There is now significant evidence that immune evasion contributes to the rapid spread of Omicron. Other factors may be a shorter serial interval (by about 0.8 to 1.2 days compared to Delta) and potential increased intrinsic transmission fitness. There is growing evidence that with Omicron, there is lower vaccine effectiveness (VE) against infection and symptomatic disease soon after vaccination compared to Delta. There is also evidence of accelerated waning of VE over time of the primary series against infection and symptomatic disease for the studied vaccines. Further studies are required to better understand the drivers of transmission and declining incidence in various settings. These factors include the intrinsic transmission fitness properties of the virus, degree of immune evasion, vaccination coverage and level of vaccine-derived and post-infection immunity, levels of social mixing and degree of application of public health and social measures (PHSM). In areas of known or suspected community or cluster transmission

# Practical Info
When adopting universal masking within a health facility, it is essential health workers follow proper mask-wearing procedures and practices. For additional information review the implementation considerations on mask management for health workers.
The WHO recommendation on mask fitting should be followed, including the related considerations on this critical aspect.

# Evidence To Decision
Strong recommendation for Very low certainty evidence
In areas of known or suspected community or cluster SARS-CoV-2 transmission, universal masking is recommended in health care facilities:
- In settings where caring for non-COVID-19 patients, unless differently specified (e.g. AGP), all health workers, including community health workers and caregivers, other staff, visitors, outpatients and service providers, should wear a well-fitting medical mask at all times within the health facility and in any common area (e.g., cafeteria, staff rooms). - Inpatients are not required to wear a medical mask unless physical distancing of at least 1 metre cannot be maintained (e.g., during examinations or bedside visits) or when outside of their care area (e.g., when being transported), provided the patient is able to tolerate the mask and there are no contraindications. - Click here for the recommendation on the mask type for health workers when caring for a suspected or confirmed COVID-19 patient.
The wearing of a medical mask is associated with a decreased risk of acquiring SARS-CoV-2 infection. In areas where there is community transmission of COVID-19, universal masking has been adopted by most hospitals to reduce potential transmission between health workers and other staff, patients, and those entering the facility. Five studies found that implementing a universal masking policy in hospital systems was associated with decreased risk of healthcare-acquired SARS-CoV-2 infection  . However, these studies have limitations, as most originated in the United States of America, and used a before-after design. Other limitations include lack of or limited control for confounders, such as the use of other personal protective equipment and exposures . Furthermore, potential sensitivity to time periods selected for analysis for pre-and post-universal masking was identified, but none of the studies included sensitivity analysis. Literature provides limited insight into the harms of universal masking; evidence on mask use, in general, indicates bothersome but non-serious harms. Therefore, despite the limitations in the evidence, the GDG judged that the benefits of implementing universal mask use in healthcare facilities outweigh potential harms.

# Substantial net benefits of the recommended alternative

# Benefits and harms
Given the limited number and the type of evidence available (i.e., before-after studies) regarding the implementation of universal masking as an IPC procedure, the certainty of the evidence is rated as very low. However, despite the very low certainty of evidence pertaining to universal masking, the wearing of a medical mask is associated with a decreased risk of acquiring SARS-CoV-2 infection.

# Very low

# Certainty of the Evidence
Given the protective effects associated with mask use, health workers, including community health workers and caregivers, would likely favour the implementation of universal masking
Upon deliberations during the GDG meeting, the decision regarding this recommendation's strength was reached through online voting. Despite the very low certainty of the evidence for the implementation of universal masking, the evidence does indicate benefits without significant harms; in addition, the GDG members judged that universal masking could prevent potential serious harms of health care worker infections and transmission in health care. Of 28 members of the GDG, 78.6% (22) voted that this should be a strong recommendation. Members also felt that based on their own professional experience, or that of colleagues, universal masking in health settings is already routine in most countries; therefore, the acceptability and feasibility favoured a strong recommendation, as well. Furthermore, the utilization of a medical mask is associated with a decrease in SARS-CoV-2 transmission.
Additionally, the GDG reviewed the mask type to be used universally in health care facilities. In light of new VOCs with increased transmissibility and the subsequent need to better protect health workers and their patients, GDG members felt the exclusive use of medical masks was justified. Given the available evidence on mask effectiveness of medical masks and their requirement to adhere to strict standards, a majority of members felt the universal use of medical masks in the health care setting would provide better protection for staff, patients, visitors and the community.
masking, some health workers may prefer to wear respirators instead of a medical mask, based on their perception of what offers the better protection to prevent SARS-CoV-2 infection and emergent evidence that the use of respirators might be more effective in the control of transmission of some variants of concern such as Omicron. There are no substantial variabilities in values and preferences.
Implementing universal masking is likely to have a low to moderate impact on resources.
No adverse impacts on equity to the individual have been identified, as long as masks are provided by health care facilities and are readily available for all health workers, staff, visitors and patients.
No important issues with the recommended alternative
Universal mask use is likely to be easily accepted in health care facilities given the protective effects for health workers, other staff, visitors and patients  .
No important issues with the recommended alternative
The universal use of masks in health care facilities is likely feasible and is currently the standard in most countries, in the context of the COVID-19 pandemic.
No important issues with the recommended alternative
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)

# Practical Info
When adopting targeted continuous masking within a health facility, it is essential health workers follow proper mask-wearing procedures and practices. For additional information review the implementation considerations on mask management for health workers.
The WHO recommendation on mask fitting should be followed, including the related considerations on this critical aspect.

# Evidence To Decision
Conditional recommendation for Very low certainty evidence
In areas of known or suspected sporadic SARS-CoV-2 transmission, targeted continuous medical mask use is recommended in health care facilities:
- In settings when caring for non-COVID-19 patients, health workers, including community health workers and caregivers who work in clinical areas, should continuously wear a well-fitting medical mask during routine activities throughout the entire shift, unless differently specified (e.g. when performing AGP) and apart from when eating and drinking. - In non-patient areas, staff are not required to wear a medical mask during routine activities if they have no patient contact.
- Click here for the recommendation on mask type for health workers when caring for a suspected or confirmed COVID-19 patient.
Given the protective effects of mask use, the benefits of implementing targeted continuous mask use in healthcare facilities outweigh potential harms. Five studies found that consistent mask use in health care facilities was associated with a decreased risk of SARS-CoV-2 infections in health workers. However, it is essential to note that these studies only investigated universal masking, not targeted continuous masking. The effects found in these studies have been extrapolated for the aforementioned recommendation .

# Substantial net benefits of the recommended alternative

# Benefits and harms
The evidence for targeted continuous masking has been extrapolated from evidence on universal masking; therefore, the certainty of the evidence is rated as very low. However, despite the very low certainty of evidence pertaining to targeted continuous masking, the wearing of a medical mask is associated with a decreased risk of acquiring SARS-CoV-2 infection.

# Very low

# Certainty of the Evidence
Given the protective effects of mask use, health workers, including community health workers and caregivers, would likely favour targeted continuous masking in health facilities  . There are no important variations in the values and preferences.
No substantial variability expected

# Values and preferences
The implementation of targeted continuous masking is likely to have a low to moderate impact on resources.
No important issues with the recommended alternative
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
After GDG members discussed their perspectives on recommending the implementation of targeted continuous masking, the decision to formalise the above statement as a conditional recommendation was reached through online voting. GDG members felt a conditional recommendation was well suited for this guidance, given that the evidence for continuous masking was inferred from evidence on universal masking and the statement is written for an epidemiological situation with few COVID-19 cases.
This intervention will likely cause no adverse impacts on equity, so long as masks are provided in health care settings and are readily available.
No important issues with the recommended alternative
The universal use of masks in healthcare facilities is the standard in most countries in the context of the COVID-19 pandemic and has been widely implemented.
No important issues with the recommended alternative
The use of targeted continuous mask use in health care facilities is likely feasible.
No important issues with the recommended alternative

# Implementation consideration
The following procedures and practices should be ensured when wearing a mask in health care settings  - Medical masks should be combined with other measures including frequent hand hygiene and physical distancing of at least 1 metre among health workers in shared and crowded places such as cafeterias, break rooms and dressing rooms. - Medical masks must be changed when wet, soiled or damaged or if the health worker or caregiver removes the mask for any reason (e.g. for eating or drinking or caring for a patient who requires droplet/contact precautions for reasons other than COVID-19). - Used medical masks should be disposed of properly.
- The medical mask should not be touched to adjust it or if it is displaced from the face for any reason. If this happens, the mask should be safely removed and replaced and hand hygiene performed. - The medical mask (as well as other PPE) should be discarded and changed after caring for any patient who requires contact/droplet precautions for other pathogens, followed by hand hygiene. - Under no circumstances should a medical mask be shared between health workers.
- Medical masks can become displaced from their optimal placement, over the mouth and nose, during extended use, which creates gaps for respiratory particles to bypass the filtration layers on inhalation and exhalation. The WHO recommendation on mask fitting should be followed, including the related considerations on this critical aspect. require additional materials. The "knot-and-tuck" and "linking-ear-loops-behind-the-head" techniques improve medical mask fit by reducing gaps on the sides of medical masks with ear loops. Such gaps allow air leakage (potentially containing infectious particles) to bypass the filtration layers of the medical mask when the wearer inhales or exhales.
Considerations on the use of linking-ear-loops-behind-the-head techniques to improve medical mask fit
- Always use a clean, unused rectangular pleated medical mask meeting the minimum performance standards (or equivalent). - Always clean hands thoroughly (per WHO guidance) prior to donning, doffing and/or manipulating a mask.
- Where connectors are used to link ear loops behind the head, ensure that these connectors are clean for use upon donning (either new, cleaned and disinfected or laundered, depending on the connector and local implementation strategy). When connectors are doffed, they should be treated as potentially contaminated. A local strategy should be in place to manage used connectors thorough cleaning and disinfection processes, laundering or discarding used connectors through standard waste management.
When adopting a mask policy, it is essential health workers follow proper mask-wearing procedures and practices. For additional information review the implementation considerations on mask management for health workers.
GDG members were asked if WHO should consider developing practical advice on improving medical mask fit, where's the majority of GDG members agreed this would be useful. Five options to improve the fit of masks were presented: the "use of ear loops linked behind the head"; the "tie-and-tuck method"; the use of a brace/fitter; the use of masks with ties behind the head instead of ear loops; double masking.
Twenty-five GDG members (83.3%) agreed with the use of ear loops linked behind the head; 23 (76.7%) agreed with the use of the tie-and-tuck method; 19 (63.3%) agreed with the use of masks with ties behind the head instead of ear loops; 16 (53.3%) agreed with the use of a brace/fitter; 10 (33.3%) agreed with double masking. Therefore, the use of ear loops linked behind the head and of the tie-and-tuck method was retained as advisable methods to improve the fit of masks and additional details can be found in the practical information section.
GDG members reported that the evidence available on improving the fit of medical masks to reduce the transmission risk of SARS-CoV-2 is in the form of laboratory-based studies with limited field and clinical investigations.

# Practical Info
When adopting a mask policy within a health facility, it is essential health workers follow proper mask-wearing procedures and practices. For additional information review the implementation considerations on mask management for health workers.
The WHO recommendation on mask fitting should be followed, including the related considerations on this critical aspect, like the type of FFR that should be used by health workers.

# Evidence To Decision
Conditional recommendation for Very low certainty evidence A respirator or a medical mask should be worn by health workers along with other PPE-a gown, gloves and eye protection -before entering a room where there is a patient with suspected or confirmed COVID-19.
Respirators should be worn in the following situations:
- In care settings where ventilation is known to be poor or cannot be assessed, or the ventilation system is not properly maintained - Based on health workers' values and preferences and on their perception of what offers the highest protection possible to prevent SARS-CoV-2 infection.
Ventilation in a health care setting is considered to be poor when the requirements established for these settings are not in place (see "Definitions" section).
Note: This recommendation applies to any setting where regular care is provided to patients with suspected or confirmed COVID-19, including home care, long-term care facilities and community care settings. For settings where AGP are regularly performed on patients with suspected or confirmed COVID-19, see the strong recommendation above.
The recommendation noted above made no distinction between the use of medical masks and respirators when caring for a COVID-19 positive patient, except in situations where respirators are clearly needed (e.g., AGP). Respirators have higher filtration efficiency standards and demonstrate better fit with fewer air gaps allowing bypass of the filter media than the most commonly used rectangular medical masks, provided that the respirators are appropriately fit tested and properly worn . Given the protective effects of respirators, several GDG members advised that respirators may be superior to medical masks in preventing SARS-CoV-2 infection and their use should be encouraged when the health care worker delivers care in close contact with the patient and/or when ventilation is inadequate.
Evidence comparing the effectiveness of respirators versus medical masks for SARS-CoV-2 in healthcare settings is limited to five observational studies  which were conducted prior to the emergence of the Delta, Omicron and other variants and before widespread vaccination in healthcare settings. These five observational studies had methodological limitations (for example, recall bias, low participation, limited measurement of exposures) and reported inconsistent findings regarding the risk of SARS-CoV-2 infection between the use of respirators versus medical masks. One study showed a reduction of risk with respirator use while in another two studies the use of respirators was not significantly associated with risk reduction . One study showed no association and another found respirators Small net benefit, or little difference between alternatives

# Benefits and harms
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
were associated with increased risk (OR 7.1), likely related to confounding factors. Prior randomised controlled trials comparing respirators versus medical masks for prevention of clinical influenza-like illness (ILI) found no difference . Overall, the strength of this evidence was rated as insufficient to recommend one type of mask versus the other.
The following side effects have been reported with respirators: discomfort, headaches, possible development of facial skin lesions, irritant dermatitis or worsening acne when used frequently for long hours. Medical masks are typically associated with less discomfort or side effects than respirators given decreased thickness and reduced seal, although this has not been quantified. Undesirable outcomes from the prolonged use of respirators were noted, including general discomfort, headaches and the development of facial skin lesions, irritant dermatitis or worsening acne. The fitting process for respirators is burdensome, and issues with achieving it have been well described. Furthermore, other factors may influence the overall risk of transmission, including general PPE use, PPE training, fit testing, ventilation, and behavioural factors (including compliance) as well as the fact that transmission of SARS-CoV-2 among health workers appears to mostly occur in community settings. The balance of desirable and undesirable outcome effects was rated as uncertain. It was deemed uncertain whether respirators are more effective than medical masks in settings without exposure to AGP.
Given the methodological limitations of the evidence, notably inconsistency and indirectness (e.g. most studies conducted before the emergence of the Delta variant and none in the Omicron era), evaluation of non-SARS-CoV-2 infections or assessment of non-clinical outcomes,  the certainty of the evidence for particulate respirators versus medical masks was rated as very low.

# Very low

# Certainty of the Evidence
There is substantial variability in preferences related to the use of respirators in preventing HAI. In the context of the increased transmissibility of the Delta or Omicron variant, some health care workers may value the wider use of respirators to potentially reduce their risk, despite the limited evidence, as a precautionary approach. Others may not prefer to wear a respirator throughout their shifts because of discomfort and potential side effects. Local values, preferences and practicalities should play an important role in directing choices on the use of respirators versus medical masks.

# Substantial variability is expected or uncertain

# Values and preferences

# Resource implications
The use of respirators for the care of all patients with suspected or confirmed COVID-19 in health care facilities requires an additional investment of financial and logistical resources, which could be challenging, in particular, in low and middle income countries. There is also the need for fit testing for all staff, requiring additional investments and expertise; however, scaling up the market for respirators could lead to cost reduction.

# Knowledge gaps, research needs and comments
Randomised controlled trials on respirators versus medical masks in health care settings are in progress. Well-conducted observational studies on respirators versus medical masks and the risk of SARS-CoV-2 infection in healthcare settings in the context of the Omicron and other variants are urgently needed. More research is also needed to investigate the risks associated with medical masks and respirators and adverse events (including self contamination) during extended and repeated use. Other gaps include studies on simpler, faster and less costly methods, or alternative methods, to determine respirator fit and seal. Further data is needed regarding compliance with appropriate PPE use, including masks, and in particular, appropriate donning and doffing practices in COVID-19 and non COVID-19 units.
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)
Omicron variant is spreading significantly faster than the Delta variant in countries with documented community transmission. Serious concerns were expressed about the evidence of SARS-CoV-2 re-infection with Omicron, and the data showing a reduction in neutralising antibody titres against Omicron and a significant reduction in VE against infection and symptomatic disease for Omicron compared to Delta. Some GDG members also highlighted the fact that as of November 2021, 65% of health workers in 135 countries were fully vaccinated, but the vaccination status was unknown for 77.7 million health workers (58% of the global health workforce).
Following in-depth discussions, the GDG was asked to decide whether to maintain the recommendation on the type of mask to be used in COVID-19 settings included in the Annex to "Infection prevention and control during health care when coronavirus disease (COVID-19) is suspected or confirmed". Out of 33 IPC GDG members who voted, 24 (68%) would have preferred to maintain the previous recommendation on the type of mask to be used in COVID-19 settings. The previous recommendation took into strong consideration serious concerns about the limited availability of respirators in low and middle income countries and the resource implications of more widespread use of respirators. The GDG voting on this recommendation in light of Omicron was based on the very low certainty of the evidence for particulate respirators versus medical masks, given the methodological limitations of the evidence, as well as the previous concerns about respirators' availability. However, among GDG members who advised maintaining the previous recommendation, 48% also stated that they would consider it acceptable to recommend either respirators or medical masks; 33% of them even considered it acceptable to prioritise respirators; the remaining 19% of them stated that no other option but maintaining the previous recommendation would be acceptable to them. 32% of the GDG members voted against maintaining the previous recommendation; among these, 70% advised recommending either respirators or medical masks, whereas 30% recommended the sole use of respirators in all settings where COVID-19 patients are given care. Given the limitations described, the deliberations of the GDG and decision-making process were also informed by the perspectives and experience of experts represented in the panel.
Following very careful interpretation of the GDG considerations and voting results which showed that 68% of GDG members would have preferred to maintain the recommendation included in the Annex issued on 1 October 2021, but also indicated what changes would have been acceptable to these GDG members, WHO decided to make this new conditional recommendation which was issued as rapid guidelines on 22 December 2021. Given the increased transmissibility and rapid spread of the Omicron VOC, WHO leadership felt it was necessary to take a precautionary approach, according to the hierarchy of controls, and add the option of respirators to the recommendation on masks to use when entering a room with a COVID-19 positive patient regardless of AGP being performed, despite the limitations of the available evidence on respirators versus medical masks in health care facilities.
Given the limited global supply of respirators and their higher cost compared to medical masks, a recommendation to use respirators for all COVID-19 cases in health care settings could result in inequity in resource limited settings. However, it is also expected that the widespread use of respirators (if available) will reduce inequities related to COVID-19 exposure risk. Unvaccinated health care workers worldwide are still at higher risk for infection, sometimes resulting in severe disease and death. There is an additional equity issue around medical masks, which may also not be available in sufficient quantities and of adequate quality in low resource settings.
Important issues, or potential issues not investigated
The current recommendation provides the option of using either respirators or medical masks, except for specific circumstances when a respirator is required. Given this flexibility, it should be acceptable for stakeholders' and policymakers'.
No important issues with the recommended alternative
Although WHO unpublished modelling data indicated an inadequate supply of respirators to replace medical masks in all COVID-19 health care settings, policies advising respirators in all COVID-19 settings would likely lead to increased investments and production. Furthermore, a strong supply distribution and logistics system is needed to ensure efficient procurement and reach across the whole health system. However, inefficiencies in the distribution of supplies and supply chain problems have been reported. The adequate fit of the device is correlated with the effectiveness of the FFP, but fit testing may not be feasible in all regions.
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)

# Practical Info
When adopting a mask policy within a health facility, it is essential health workers follow proper mask-wearing procedures and practices. For additional information review the section on mask management for health workers.
The WHO recommendation on mask fitting should be followed, including the related considerations on this critical aspect.

# Evidence To Decision

# Strong recommendation for Very low certainty evidence
A respirator should always be worn along with other PPE by health workers performing aerosol-generating procedures (AGP) and by health workers on duty in settings where AGP are regularly performed on patients with suspected or confirmed COVID-19, such as intensive care units, semi-intensive care units or emergency departments.
PPE includes gown, gloves, eye protection.
Among health care workers, exposure to an AGP such as tracheal intubation was associated with a higher risk of infection with SARS-CoV-1, the most closely related human coronavirus to SARS-CoV-2. Furthermore, a living rapid review showed that certain exposures such as involvement in intubations are significantly associated with SARS-CoV-2 infections. However, no specific evidence assessing the effectiveness of different types of masks to prevent transmission of SARS-CoV-2 during AGP is available. Indirect evidence from laboratory simulation data provides insight on the plausibility and viability of aerosolised SARS-CoV-2.
Respirators have higher filtration efficiency standards and demonstrate better fit with fewer air gaps allowing bypass of the filter media than the most commonly used rectangular medical masks, provided that they are appropriately fit tested and worn. Therefore, respirators are likely to be superior in preventing transmission of SARS-CoV-2 during AGP.
Small net benefit, or little difference between alternatives

# Benefits and harms
Given the absence of direct evidence related to SARS-CoV-2 and the limitations of the indirect evidence, the certainty of the evidence for the utilization of particulate respirators for patients with suspected or confirmed COVID-19 during AGP was rated as very low.

# Very low

# Certainty of the Evidence
Health care workers would highly prefer to wear a respirator during AGP in order to benefit from the perception of a higher protective effect. Thus, no variability is expected in health care workers' preferences related to the use of respirators during AGP to prevent transmission risk in preventing transmission.
No substantial variability expected

# Values and preferences

# Resource implications
The use of respirators requires an additional investment of financial and logistical resources, including the need for fit testing for all staff, requiring additional investments and expertise. Some clinical and operational challenges may be experienced, in particular in low and middle income countries, and investments are needed in order to provide the best protection possible during AGP.
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)
A majority of GDG members noted that despite the very low certainty of evidence, the acceptability and feasibility of implementation and the benefits of wearing a respirator during the performance of an AGP on a suspected or confirmed COVID-19 patient justified a strong recommendation. The GDG agreed to upgrade the strength of this recommendation from a conditional recommendation to a strong recommendation. The decision was made in light of the increased widespread transmission of Omicron, its immune escape, and still limited vaccination coverage in health care workers worldwide.

# Knowledge gaps, research needs and comments
Additional research is needed to clarify which medical procedures produce aerosols and thus, potentially increase the transmission risk of SARS-CoV-2 and other respiratory pathogens thus, leading to the need for a higher level of respiratory protection. Conducting trials to compare the effectiveness of different types of masks to prevent infection during AGP would be unethical.
Given the limited global supply of respirators and their high cost in particular for resource-limited settings, inequity issues likely exist.
Important issues, or potential issues not investigated
Stakeholders and policymakers' will likely accept the recommended use of respirators during procedures that produce aerosols as this is the policy currently in place in most countries and historically integrated into a conditional recommendation by the WHO for acute respiratory infections.
No important issues with the recommended alternative
The use of respirators during the performance of an AGP is feasible although some resources implications have been noted.
No important issues with the recommended alternative
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)

# Mask use acknowledgments Funding
Funding for the development of this document was provided by the United States Centers for Disease Control and Prevention (US CDC), in addition to WHO core funds. However, the views expressed in this guidance do not necessarily reflect the official policies of the US CDC.

# Authorship, contributions, acknowledgements
WHO would like to thank the collaborative efforts of all those involved to make this process rapid, efficient, trustworthy and transparent.

# WHO Health Emergencies Programme COVID-19 Infection Prevention and Control Secretariat (alphabetically)

# WHO Health Emergencies Programme COVID-19 Infection Prevention and Control Steering Group (alphabetically)

# UNICEF Steering Committee Observers
Nagwa Hasanin (UNICEF), Raoul Kamadjeu (UNICEF), Pierre Yves Oger (UNICEF).

# WHO Health Emergencies Programme COVID-19 Infection Prevention and Control Guideline Development Group (alphabetically)

# Declaration of conflicts of interest
Dr R. Chou is an author on some of the evidence used to inform some recommendations. However, as a methodologist, he provided guidance to the GDG on methodologic issues and is not a voting member of the GDG. In some meetings, he presented evidence and provided clarification on methods to guide discussions regarding the EtD tables; however, all decisions were made by voting members of the GDG.

# Temporary Advisor
Fernanda C. Lessa (US Centers for Disease Control and Prevention, United States of America).

# Declaration of conflicts of interest
Dr F. Lessa is an employee of the United States CDC which has provided funding towards the development of this guideline. After consulting with the WHO Ethics Committee, it was determined Dr Lessa would contribute to discussions as she brings significant technical and field expertise to the discussions; however, be recused from voting on recommendations.

# External reviewers (alphabetically)

# PPE Technical Specifications
Pertinent sections of the technical guidance, "Technical specifications of personal protective equipment for COVID-19", published 13 November 2020, will soon be incorporated in this living guidance.

# Prevention, identification and management of SARS-CoV-2 infections in health and care workers Background
The COVID-19 pandemic has placed a large burden on health systems worldwide and, in turn, affected hospital-acquired infections and health and care workers. Health and care workers are at higher risk than the general public of being infected with SARS-CoV-2.
Prevention of infections in the health care setting requires a multi-pronged and multi-factorial approach that includes IPC and occupational health and safety (OHS) measures as well as adherence to public health and social measures in the community by the health workforce. In hospitals, this involves the hierarchy of controls (hazard elimination, engineering/environmental controls, administrative controls, and the optimal use of PPE) and, for IPC and OHS staff, to work collaboratively to implement these protocols. See the section on What is an IPC programme and section on Introduction to public health and social measures for additional information.
This updated section of the WHO guidelines on Infection Prevention and Control in the Context of COVID-19 provides guidance to health managers and OHS teams on the following topics:
- how COVID-19 infections in the health-care setting or during the provision of care can be prevented;
- how COVID-19 infections can be identified;
- once they occur, how COVID-19 infections can be managed safely to prevent onward transmission to other health and care workers or patients in the health-care setting.
The underpinning basis for all these statements is the notion that the early identification, and thus testing and quarantining of health and care workers and/or other control measures aim to decrease the risk of nosocomial infection.
This version of the living guideline (version 5.0) supersedes the previous guidance on the prevention, identification and management of health and care worker infections in the context of COVID-19, issued in October 2020.

# Prevention of health and care worker infections in the health care setting Practical Info
When considering a national testing strategy, the following contextual factors should be considered :
- Strategies outlined in the OHS and/or IPC national policies should include implementation plans that ensure health and care worker testing is prioritized and made available in health care facilities. This should include laboratory testing and self-testing kits for SARS-CoV-2 infections. - OHS and IPC programmes should include a committee of multidisciplinary experts to guide policies and protocols implemented by employers/management teams and demonstrate through staff adherence. - The local situation should be evaluated by considering dynamic indicators: SARS-CoV-2 epidemic trends, transmissibility, the seriousness of COVID-19 and the impact on the health system.

# Good practice statement
Countries should have national and subnational testing strategies for the detection of SARS-CoV-2 infections in health and care workers.

# Implementation consideration
Practical impacts and consequences of identifying positive COVID-19 cases in health and care workers (including potential absences due to sick leave, or isolation, as well as the absence of the health workforce) and the ability to manage infections and a safe return to work need to be considered. Furthermore, health care facilities may consider providing self-testing kits to health and care workers; testing free of charge on-site; testing health and care workers post-exposure; testing in settings with vulnerable patients (e.g. ICUs and transplant units); and testing all health and care workers who have signs or symptoms suggestive of COVID-19. These testing strategies for the health workforce population should consider the availability of testing kits and the feasibility of carrying out testing, as well as the impact on health systems and services of detecting active infections and having those workers stop working while they isolate (see sections 6.2.2 and 6.4.2).
For guidance on testing strategies for SARS-CoV-2, refer to Use of SARS-CoV-2 antigen-detection rapid diagnostic tests for COVID-19 self-testing.
GDG members noted the importance of having national and subnational testing strategies for SARS-CoV-2, including in the health workforce. Having testing mechanisms in place allows for the quick identification and swift removal from work and isolation of health and care workers with SARS-CoV-2 infections, thus decreasing the risk of nosocomial transmission.

# Identification of health and care workers infections in the health care setting Practical Info
The GDG members recommended that passive screening for SARS-CoV-2 should be combined with screening for other respiratory viruses (e.g. influenza). Early detection of COVID-19 infection among health and care workers can be achieved through passive syndromic screening when combined with laboratory testing, to confirm infection. Surveillance is generally seen as a best practice in the field of IPC as a key to preventing secondary transmission (otherwise referred to as nosocomial transmission) to patients, between health and care workers and throughout health care settings.
Syndromic screening can be conducted using passive or active methods. The selection of the appropriate method depends on the health care facility's capacities and the levels of local circulation of the virus. In passive screening, health and care workers self-screen for symptoms and are required to report any concerning symptoms. Active screening includes others screening the health and care workers for symptoms, this process demands a heavy use of resources, which often only yield a low number of positive cases.
The key objectives of screening in the current context are:
- to identify possible cases and clusters of infections;
- to implement containment measures to prevent onward transmission, such as quarantine or isolation and IPC measures;
- to identify the source of infection (whether hospital-acquired or community-acquired).
Definitions of syndromic screening, passive screening, and active screening can be found in the definitions section.
Health and care workers who report any of the symptoms associated with COVID-19 or other acute respiratory illnesses should contact their local OHS service or IPC department for guidance on testing and quarantine/isolation processes. Health New Implementation consideration care facilities should ensure that employment policies be in place, such as paid sick leave, having the ability to stay home, work from home or rest. These policies should guarantee confidentiality and be non-punitive for health and care workers who become infected with SARS-CoV-2 or contacts of a case.
GDG members discussed that surveillance of health and care worker infections is a best practice in any health care setting, even outside SARS-CoV-2. They noted the importance of having a system established and policies allowing health and care workers to report any symptoms suggestive of respiratory infections, including SARS-CoV-2, to be referred for testing and abstain from physical presence in the workplace without onus.
There is evidence that symptoms of COVID-19 1 are the best indicators of active infection and indicate that the symptomatic person is in the most infectious period of the course of the disease .
Thus, identifying these health and care workers early and testing them and/or preventing them from attending their shift can break the transmission chain and limit the nosocomial transmission of SARS-CoV-2 .
The term passive screening was proposed by the GDG as a method for health workers to self-screen for symptoms and potentially identify infections in the health setting. They agreed that screening refers to the identification of unrecognized SARS-CoV-2 infections using tests, self-examinations, or related procedures. Screening of health and care workers should identify risk factors and prodromal symptoms for early evidence of infection. GDG members concurred that passive screening, versus active screening, was preferred. Their justification was the potential cost savings and reduced burden on health administration and health and care workers by allowing them to perform their own syndromic surveillance and control their own health and well-being.
They noted the importance of establishing policies that would allow health and care workers to report any symptoms suggestive of respiratory infections, including SARS-CoV-2, to be referred for testing and to abstain from physical presence in the workplace without onus.
Information on screening, triage and early recognition of patients with COVID-19 can be found in section 6 of the clinical management of COVID-19: living guideline.
See "Section 6: Management of health and care worker infections in health settings" in this document for additional information. 1 Refer to WHO COVID-19 Case Definition for the most up-to-date list of COVID-19: fever, cough, general weakness/ fatigue, headache, myalgia, sore throat, coryza, dyspnoea, nausea, diarrhoea, anorexia. Symptoms may be non-specific to COVID-19 and may also indicate other influenza-like illnesses for which health and care workers should be referred to their local guidance on those diseases.

# Practical Info
Health and care workers should be included in the health-care facility testing strategy. For example, testing could occur as a follow-up to signs or symptoms of COVID-19 following a high-risk exposure to a patient or colleague positive for SARS-CoV-2, or for routine testing. WHO's guidance on testing for SARS-CoV-2 stresses that health and care workers who work in COVID-19 services or facilities have the highest priority, followed by health and care workers prioritized by risk in other
Health and care workers are considered a priority group for testing, according to key WHO documents on testing strategies and diagnosis of SARS-CoV-2 infection. Based on these WHO guidance documents, the decision to formalize the above statement as a GPS was reached through discussions with the GDG and online voting. GDG members noted that health and care workers should constitute a priority population since they are at high risk of SARS-CoV-2 acquisition due to the nature of their work and their interaction with infected patients. Furthermore, if infected, they represent a risk for patients, especially those at risk for COVID-19 complications. Prioritizing health and care workers for SARS-CoV-2 testing allows for their quick identification and exclusion from in-person work; thus, preventing onward transmission to high-risk patients or other health and care workers.

# Practical Info
Health and care workers should be encouraged to report both occupational and non-occupational exposures to COVID-19 to OHS or an equivalent department.
OHS teams, along with IPC focal points, should create comprehensive and clear protocols so that health and care workers are able to quickly report high-risk exposures. These protocols should provide details on the essential information to include in the report (such as situational events, symptoms, contacts and exposures) and the mechanism for submitting the report, including next steps and follow-up actions.
The protocols should include instructions for health and care workers to wear a medical mask as soon as they recognize they are symptomatic; refrain from their work activities; and report to their OHS/IPC focal point. The focal point should suggest that the symptomatic health and care workers quarantine in a designated setting until testing is carried out; they know what their status is; and can determine how to move forward.
The OHS team or the IPC focal point should:
- meet with the health or care worker to assess their symptoms and record exposure history (where resources permit);
- ask the health or care worker to complete and submit the form for the WHO Risk assessment and management of exposure of health care workers in the context of COVID-19; - identify a risk categorization based on the risk assessment tool for a health or care worker who has had an exposure without proper use of PPE and determine appropriate management, including the health or care worker's ability to continue working or to be excluded from in-person activities; - arrange for testing following a high-risk exposure (see section 6.3).
Strategies to mitigate workforce shortages should be in place in the event that health and care workers are required to remain off work due to quarantine or isolation.

# Good practice statement
Health care facilities should have protocols for reporting and managing health and care workers' occupational and non-occupational high-risk exposures to COVID-19.
GDG members discussed the importance of having protocols in place to facilitate the reporting of high-risk exposures to SARS-CoV-2 and their rapid and appropriate management. Referral to OHS and/or IPC services after high-risk exposures to SARS-CoV-2 is critical for early diagnosis of the infection in health and care workers and for minimizing the spread of infections to other colleagues and patients in a health-care setting. The WHO COVID-19: Occupational health and safety for health and care workers interim guidance  advises that workplace risk assessments be carried out by OHS and IPC to determine which roles are at high risk for exposure in health care facilities, how well health and care workers are to return to work; and how health and care workers can conduct their tasks safely upon their return. High-risk exposures are largely avoidable in health-care settings where protocols and best practices are adhered to by all. If they do occur, they need to be followed up and learned from. High-risk exposure definitions can be found in the definitions section of this guideline.
Preventing hospital-acquired infections requires a multi-pronged, comprehensive approach that involves a hierarchy of controls (hazard elimination, engineering/environmental controls, administrative controls and optimal use of PPE) and for IPC and OHS staff to work collaboratively to implement these protocols.

# Practical Info
Identifying health workers positive for SARS-CoV-2 infection can be achieved through nucleic acid amplification tests (NAATs), such as real-time reverse-transcription polymerase chain reaction (rRT-PCR) tests, which are the most sensitive and specific tests for diagnosing COVID-19. Otherwise, antigen-detection rapid diagnostic tests (Ag-RDTs) are recommended as a viable alternative to confirm SARS-CoV-2 infection, especially in settings where NAAT is not available or results are not timely. Facilities can follow the WHO guidance for testing or WHO policy brief: COVID-19 testing (14 September 2022).
Health and care workers who are positive for SARS-CoV-2 infection should isolate themselves at home (if they are able to safely isolate and their clinical condition) or in a designated setting such as a health-care facility or non-traditional isolation facility, depending on the country's approach. This decision of where to isolate should be made in conjunction with local public health policies and with their health care practitioner.
Health and care workers are required to isolate for the duration of time outlined in their local public health policies or they can follow WHO recommendations for the duration of isolation, which can be found under section 4 (COVID-19 care pathway) and include options for using testing as a tool to enable an earlier return-to-work.

# High-case load scenarios
Health-care facility administrators will need to balance the risk of excluding essential health and care workers, which may contribute to facility-wide shortages, against the risks of possible onward transmission to patients and other health and care workers according to the transmission scenarios in the facility and community. They may do this by choosing to assess infected health and care workers on a case-by-case basis and assess their infectiousness based on symptoms and test results

# Good practice statement
Any health or care worker who has signs or symptoms 1 of SARS-CoV-2 infection 2 should be excluded from their activities at work that require providing in-person care to patients or other activities in the health-care facility where they are in contact with other health and care personnel.
They should furthermore consult with their occupational health and safety department and plan for isolation in a designated setting for the duration of the required period of isolation outlined by their local policy 3.

# Implementation consideration
for earlier return-to-work options and select appropriate units in which these health and care workers may work. For example, high-risk units such as ICUs, transplant units and oncology units may need to be excluded.
Health care facility administrators should ensure adequate supplies of PPE are available for health and care workers and that processes are in place for monitoring and evaluating IPC procedures, including fit testing, and correct donning and doffing of PPE and its disposal.

# OHS Follow up
Focal points for occupational health and safety should perform workplace risk assessments to determine if an infection was acquired in the health care facility. If it is related to an occupational exposure such as a breach in IPC practices, appropriate corrective measures, such as refresher training on IPC measures, should be put in place to address breaches.

# Return to work
Upon return to work after an infection, health and care workers should continue to follow strict IPC measures; hand hygiene practices; wearing a mask when indicated; wearing of PPE when indicated; and other practices outlined in this guideline. The length of isolation should be determined by the health facility and local guidance for the period of infectiousness. Alternatively, administrators can refer to WHO guidance listed in section 6.
The decision to formalize the above statement as a good practice statement was reached through in-depth GDG discussions and online voting. Many GDG members noted that health and care workers who have symptoms of SARS-CoV-2 infection pose a high risk of being infectious and thus transmitting the virus to patient populations most at risk of developing complications (those with co-morbidities, of older age or with compromised immune systems).

# Testing after high-risk exposures and recommendations for quarantine duration for health and care workers Practical Info
Quarantine arrangements can be implemented at home or in another designated setting where the contact can be regularly Refer to the WHO Contact tracing and quarantine in the context of COVID-19: interim guidance for recommendations on testing after a high-risk exposure and the length of quarantine for contacts of COVID-19 cases which may be applied to the health and care worker population. WHO advises that identification, contact, quarantine and follow-up of individuals at high risk of acquiring SARS-CoV-2 infection who have been in contact with a confirmed or probable case of SARS-CoV-2 infection should be prioritized rather than targeting all contacts.
Health and care workers are a priority population. They should receive support regarding quarantine measures and access to free or affordable and reliable testing (including self-tests).
Table 4 presents a summary of the quarantine scenarios for health and care workers according to vaccination status.

# Extracted from the WHO Contact tracing and quarantine in the context of COVID-19: interim guidance for recommendations on testing after a high-risk exposure and the length of quarantine for contacts of COVID-19 cases which may be applied to the health and care worker population.
New monitored for signs and symptoms. During quarantine, adequate ventilation and IPC measures should be implemented and maintained.
Quarantined individuals must be supported with adequate food, water, protection, hygiene, and communication provisions, including access to education, paid leave or remote work options. In addition, they need to regularly monitor their health status for symptoms and receive clear instructions on what to do in case they develop signs and symptoms of COVID-19. The instructions need to include referrals to call centres, health care centres or medical staff in case of need as well as testing facilities or self-testing options for the contacts.
All contacts in quarantine who develop signs and symptoms need to undergo testing. Staff supporting contacts in quarantine, either through in-person visits or through call centres, need to be trained to assess and manage them or refer the contacts to needed support.
If other people enter the room of a contact in quarantine, physical contact should be avoided, and face masks should be worn by all parties, unless contraindicated (e.g. in infants). Quarantined individuals should avoid contact with people at high risk of detrimental COVID-19 outcomes.
More implementation considerations can be found at the WHO Contact tracing and quarantine in the context of COVID-19: interim guidance. If, in the last 90 days, a vulnerable contact or someone in a priority setting has been vaccinated (i.e. has completed the primary series and/or received a booster dose) or has experienced a confirmed SARS-CoV-2 infection, this contact is not considered to be at high risk of infection or further transmission.
Vaccinated/infected more than >90 days

# Quarantine for 10 days
Quarantine for 5 days plus negative test

# High case load scenarios

# No quarantine required
When the case load is high, and many health and care workers and essential workers are off work due to exposure or infection, health systems may be overstretched. In that context, vaccinated health and care workers and other essential workers who are asymptomatic contacts may have a shortened quarantine or continue to work without quarantine.
Daily Ag-RDT testing may be performed up to day 5 after exposure.

# Extracted from the WHO Contact tracing and quarantine in the context of COVID-19: interim guidance for recommendations on testing after a high-risk exposure and the length of quarantine for contacts of COVID-19 cases which may be applied to the health and care worker population.
New Implementation consideration

# Duration of isolation for COVID-19 cases in health and care workers Practical Info
It is advised that health facilities have local protocols to advise on the required duration of isolation, testing options and for return-to-work management.
Upon termination of the isolation period, it is advised that health and care workers have a medical assessment in conjunction with OHS and IPC services to determine whether the individual is fit to return to work safely. These should include factors such as (but not limited to):
- their work setting (dedicated to COVID-19 patients, ICU, or long-term care versus direct patient care or non-patientfacing care) - clinical conditions of the patients (e.g. immunocompromised) for whom the health and care worker may provide care - health facility IPC measures and use of universal masking as per WHO Advice on the use of masks in the context of COVID-19 guidance - the health and care worker's general health and severity of previous illness with COVID-19.
Testing to reduce the length of isolation is dependent on local policies and could be used during an outbreak or high health workforce absenteeism, based on availability, feasibility, and economic abilities of the health care facility to provide testing to staff. In scenarios where health care facilities choose to accept that health and care workers return to work before the recommended timelines and the conclusion of the period of infectiousness, health and care workers should strictly adhere to standard and transmission-based precautions and consider working on COVID-19 wards or non-high-risk wards to reduce any risk of onward transmission to patients and staff.

# Conditional recommendation for Very low certainty evidence
We suggest 10 days of isolation for individuals who are symptomatic due to SARS-CoV-2 infection (very low certainty evidence).
We suggest 5 days of isolation for individuals who are asymptomatic with SARS-CoV-2 infection (very low certainty evidence).
We suggest the use of rapid antigen testing to reduce the period of isolation (very low certainty evidence).

# For the most up-to-date evidence-based recommendations on the length of isolation for positive COVID-19 cases see the WHO
Clinical Management of COVID-19: living guideline, which has been directly applied to the health and care worker population; recommendations remain the same for anyone who becomes a COVID-19 case.
The current version was updated in January 2023: /#/guideline/6668/section/118562.
New There should also be occupational health policies in place to ensure health and care workers who are off work for isolation purposes, have covered sick leave and are not penalized or negatively impacted by their infection. This will ensure that health and care workers report infections and do not attend work when sick. OHS and IPC staff will need to balance the risk of essential health and care worker shortages against the risks of exposure and implementation of work restrictions according to the transmission scenarios in the facility and community.
Health and care workers should adhere to the following recommendations when returning to work after a COVID-19 infection:
- Attend refresher training on IPC practices such as hand and respiratory hygiene, fit test and fit check of respirators, PPE use, masking policies and safe physical distancing. - Continue to follow public health and social measures in their home and community settings.
- Continue to self-monitor for symptoms suggestive of COVID-19 and immediately stop working, report to their OHS department and self-isolate if new or worsening symptoms develop/re-appear. - Health and care workers should receive ongoing support and monitoring from OHS for longer-term health complications and potential psychological implications.

# Evidence To Decision
See below for a copy of the evidence to decision table, for source and any other information see Clinical Management of COVID-19. The current version has been published in January 2023: /#/guideline/6668/ section/118562
Isolation Period: The benefits outlined by the GDG relate to the impact on subsequent hospitalization and mortality across contacts (very low certainty evidence) of a 10-day, compared with a 5-day, isolation period for symptomatic individuals. Symptomatic individuals are much more likely to test positive than asymptomatic individuals and thus much more likely to transmit SARS-CoV-2. This provides the rationale, despite the very low certainty evidence on the impact of isolation on subsequent transmission, hospitalization, and mortality, for the suggestion for 10 days in symptomatic and 5 days in asymptomatic cases. A shortened isolation period, where safe, was agreed-upon as preferable as part of the values and preferences, which further informed the recommendation for 5 days of isolation for asymptomatic individuals.
Harms of varying periods of isolation, such as mental health, financial or social impacts, were not formally incorporated into the evidence review, given the uncertainty involved.
Antigen testing: The possible benefit is on average a reduction of 3 days of isolation period by using rapid tests to determine the period of isolation (very low certainty evidence).
There are minimal harms of employing rapid tests to determine the period of isolation.

# Benefits and harms
Isolation Period: The evidence reviewed to inform this recommendation was deemed to be of very low certainty, rated down due to the high degree of uncertainty in the parameters that inform the model and the indirectness of the data. Specifically, there is a great deal of uncertainty across the following assumptions: i) the infectivity of individuals with positive rapid antigen test; ii) the effective reproduction number; iii) the assumed hospitalization rate of infected individuals; and iv) the assumed case-fatality rate of infected individuals. Additional sources of uncertainty lie in understanding the contributing role of different public health measures in place in different regions of the world, vaccination status, history of prior infection and the infecting SARS-CoV-2 VoC and resultant changes to infectivity and severity. Evidence was reviewed regarding the duration of viral culture positivity and PCR positivity, which were in both cases deemed to be of very low certainty.
A large source of uncertainty, as voiced by the GDG and not consistently defined in the available evidence, was the definition of what constituted symptomatic infection. From clinical experience, noted by the GDG, classifying patients as either symptomatic or asymptomatic was not always straightforward.

# Antigen testing:
The evidence was of very low certainty, rated down for indirectness and uncertainty in the included model parameters. Additional sources of uncertainty from the above recommendations that were not formally evaluated Very low

# Certainty of the Evidence
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)
The clinical management team and respective GDG assessed the evidence and determined the updated recommendations for the suggested duration of isolation timelines. They then were asked to then present their findings and summary of evidence to the IPC GDG, who agreed that due to limited evidence on the risks of onward infection transmission among different populations, such as health and care workers, there was no need to make different recommendations for health and care workers.
The Clinical Management GDG reviewed the evidence for onward transmission that may lead to hospitalization or death following contact with persons isolated for five days versus 10 for both symptomatic and asymptomatic cases and found there were differences between symptomatic and asymptomatic individuals and therefore decided to make separate recommendations for these two groups, although it may be initially difficult to classify cases into these categories. The Clinical Management GDG discussed that hospitalization and mortality among contacts remain the crucial outcomes for consideration.
included evaluations of the sensitivity and specificity of various types of rapid tests, the swab technique employed, vaccination status, history of prior infection and the infecting variant, leading to greater uncertainty as assessed by the GDG.
- Given anticipated strong preferences in most individuals for shorter periods of isolation, and its positive social and economic consequences, the Clinical Management GDG placed a high value on shorter periods of isolation. - Despite the very low certainty evidence, the Clinical Management GDG placed a high value on the possible increase, in symptomatic patients, of transmission and resulting hospitalization in secondary infections resulting from a shorter period of isolation. - The GDG nevertheless acknowledged the substantial variability in these values and preferences that are likely to exist.
Antigen Testing: Given anticipated strong preferences in most individuals for shorter periods of isolation, and the positive social and economic consequences of shorter periods of isolation, the Clinical Management GDG placed a high value on shorter periods of isolation.
The Clinical Management GDG nevertheless acknowledges the substantial variability in these values and preferences that are likely to exist.

# Values and preferences
Isolation Period: The GDG emphasized that there are substantial resource considerations in asking individuals with mildly symptomatic disease to isolate for 5 days. These resource considerations should be incorporated into policies to ensure that the impact of periods of isolation on individuals is minimized as it relates to financial, social, or mental health-specific impacts.
Antigen Testing: The GDG acknowledged that the resource implications of prolonged periods of isolation may be considerable and reach beyond the individual, with varying social, economic, and mental health impacts. Implementation of the above recommendations should incorporate policies to ensure those considerations are addressed.

# Resources and other considerations
Clinical Question/ PICO

# UNICEF Steering Committee Members Observers
Nagwa Hasanin (UNICEF), Raoul Kamadjeu (UNICEF), Pierre Yves Oger (UNICEF). Declarations of interest of external reviewers were collected and assessed, and no conflict of interest was identified for these thematic areas.

# WHO Health Emergencies Programme COVID-19 Infection Prevention and Control Guideline Development Group (alphabetically)
Infection prevention and control in the context of coronavirus disease (COVID-19): A living guideline -World Health Organization (WHO)