Rationale and aim

Methodological approach

　TABLE 1 Different study designs contributing to mask research
　(Laboratory studies, Randomized controlled trials, Observational
　designs and modeling, Social and psychological studies)

Transmission of respiratory infections

　Box 1: Flawed assumptions and logical fallacies about airborne transmission

　TABLE 2 Summary of how laboratory studies have contributed to mask research

What are masks and how do they work?

Standards and certification

　Fig 1 Synthesis of the measured fit factors and protection factors for various types of
　face coverings, based on the 12 primary studies

　Fig 2 Median of the total inward leakage over all participants for different cases

Methodological challenges in trials and meta-analyses of masks

　Nature of the outcome

　Seasonal and year-on-year variation

　Variable primary outcomes

　Combining dissimilar interventions

　Combining different settings

　Combining heterogeneous outcomes

　A new meta-analysis: justification of approach

Reanalysis of RCTs of masks in community settings

　TABLE 3 RCTs of masks and respirators in community settings

　Fig 3 Forest plot of community trials: medical masks vs control (no masks).

　Fig 4 Forest plot of community trials: hand hygiene + medical masks vs control.

Reanalysis of RCTs of masks and respirators in health-care settings

　TABLE 4 RCTs of masks and respirators in health-care settings

　Fig 5 Forest plot of trials in health-care workers: any use of N95 vs medical masks.

　Fig 6 Forest plot of trials in health-care workers: continuous use of N95 vs medical masks.

Comment

Observational studies

Modeling masking

　Fig 7 Model of mask effectiveness in different levels of population assortativity.

Introduction and general adverse effects

Discomfort and local irritation

Effects during exercise

Speculated but unconfirmed harms in anti-mask discourse

Adverse effects of masks in people in particular risk groups

　Children; Adults with medical conditions

　TABLE 5 Medical conditions requiring caution with masking

Masks and communication

Why people mask and why they don’t

Communicating information and managing misinformation about masks

Different types of mask policies

　Mask policies for targeted personal protection

　Mask policies for specific settings

　Mask policies for seasonal respiratory infections

　Mask policies for pandemics　

Developing and implementing mask policies

　TABLE 6 Developing and implementing mask policies for respiratory pathogens

The scale of environmental harm

Mitigating environmental harm from single-use masks and respirators: what can be done?

　Increase public awareness

　Improve mask waste management

　Recycle mask waste

　Promote reuse and extended use

　Normalize elastomeric respirators

　Develop biodegradable and reusable masks

　Formulate relevant policies and regulation

Toward better masks

　Box 2: Some suggestions for a new generation of research on masks and respirators