Speakers
Runar Solberg, PhD
Scientist
Centre for Epidemic Interventions Research (CEIR)
Norwegian Institute of Public Health
Atle Fretheim, PhD
Research Director
Norwegian Institute of Public Health
Keywords
Face Masks; Masking; Respiratory Infection; Public Health; COVID-19
Key Points
- Observational evidence supports a reduction in respiratory infection with face mask use. However, randomized trials face challenges–especially in achieving sufficient statistical power–that contribute to uncertainty in their findings.
- The study team conducted a pragmatic randomized trial aimed at assessing the personal protective efficacy of wearing a surgical face mask in public settings.
- Adherence varied between the control and intervention groups, with higher rates of adherence within the control group (no mask).
- Participants were recruited from multiple locations across Norway. Advertising and the researchers’ appearance on Norwegian television, radio, and other media helped raise awareness about the study.
- Reviewers acknowledged that the primary outcome–self-reported respiratory symptoms–was clinically meaningful and well-defined. However, the reliance on self-reported data led to concerns about bias and accuracy, as there was no in-person verification of masking.
- To mitigate these concerns, future studies may opt to use registry data or incorporate mandatory PCR testing of participants.
Discussion Themes
An open and important question about masking effectiveness relates to the durability of the intervention: Does it flatten the curve early or delay the peak?
Collecting data on components of the primary outcome–i.e. if more objective symptoms like fever were more or less impacted by the intervention than more subjective outcomes like malaise–may help address concerns about the reliability of self-reported outcomes.
Efficacy depends on the degree of risk. Proving efficacy in a randomized controlled trial or pragmatic trial is tricky unless there is something to prevent. This depends on many factors that may cause heterogeneity of treatment effects (e.g. degree of exposure, physical proximity, virulence, etc.).