Community-Level Mask Promotion — COVID-19
Yale / Stanford research partnership with Bangladeshi NGOs · Bangladesh · 2020
Summary
The largest cluster-randomized trial of community masking ever conducted found that free mask distribution alone had little effect, but pairing distribution with in-person monitoring and promotion in public spaces produced large, sustained increases in mask adoption. Surgical masks outperformed cloth masks in reducing symptomatic transmission. The study provides the clearest causal evidence of community-level masking effectiveness during COVID-19.
Research question
"Can community mask distribution and monitoring increase mask-wearing and reduce SARS-CoV-2 transmission?"
Methodology
Intervention
Free surgical mask distribution + periodic in-person monitoring and promotion at public locations
Assignment
Cluster randomized trial (village)
Sample size
341,830 adults across 600 villages
Primary outcome
Mask-wearing rates; symptomatic SARS-CoV-2 seroprevalence
Effect estimate
Mask-wearing increased from 13% to 42% in treatment villages; symptomatic COVID-19 reduced by ~11%; symptomatic seroprevalence reduced by ~9% (larger effects for surgical vs. cloth masks)
Decision
Results informed WHO and national mask guidance; surgical mask provision prioritized over cloth
Result
Positive
Mask-wearing increased from 13% to 42% in treatment villages; symptomatic COVID-19 reduced by ~11%; symptomatic seroprevalence reduced by ~9% (larger effects for surgical vs. cloth masks)
Evidence strength
Limited
Observational or pre-post design; correlation not necessarily causal.
Replication status
Partially replicated
Institution
Yale / Stanford research partnership with Bangladeshi NGOs
Location
Bangladesh
Year
2020
Policy area
Public Health
Mechanism
Information