The primary goal of the village-level intervention is to assess whether mask-wearing reduces community-level COVID-19 seroconversion. The individual experiment assess whether masks protect against COVID-19 seroconversion. It also assesses the efficacy of high-quality cloth vs. surgical masks.

This study intends to answer the following research questions:

Can mask distribution and mask promotion at homes, mosques, markets and other public areas successfully change community mask-wearing norms to increase mask-wearing?

Can community mask-wearing reduce COVID-19 seroconversions?

Can mask wearing reduce COVID-19 seroconversions for the wearer?

Are high-quality cloth or "surgical" masks more effective in reducing COVID-19 seroconversions?

Is increased prevalence of community-level mask-wearing associated with decreased physical distancing?

To answer these questions, the investigators will conduct a cluster randomized trial which randomizes the proposed intervention at the village level in Bangladesh, as well as a separate trial where masks are randomized at the individual level among high-risk indoor market vendors.

In the community experiment, control communities will receive no intervention and treatment communities will receive an extensive intervention combining several elements. The investigators will distribute free face masks through door-to-door visits and at markets and mosques. Some communities will receive cloth masks and some will wear surgical masks (cross-randomized among intervention communities). Mask promoters in the community and at markets in treated villages will remind people about the importance of wearing masks and distribute additional masks. Markets will have signs that masks need to be worn to enter the market. Religious leaders will encourage mask use at religious services. Communities will receive an incentive if >75% are observed to wear masks by mask surveillance staff that conduct discrete observations on days when mask promotion is and is not occurring. The project will enroll 600 communities and create matched pairs based on population size; half of which will be randomized to receive the intervention.

In the individual experiment, the investigators will identify 5,000 high-risk individuals (vendors at indoor market). and randomizing them at the individual level to receive our mask intervention or not. In each indoor market, there will be both control and treatment individuals. Individuals in the treatment arm will receive a free face mask (cloth or surgical). Investigators will enroll individuals from 350-500 markets that are not in the communities that are participating in the community experiment.

Communities will be surveilled at 0, 1, 2, 4, 6, 8, and 12 weeks to assess mask wearing. Participants in the indvidual experiment will be surveilled at 0, 1, 2, 4, 6, weeks to assess mask wearing.

In both experiments, we will assess seroprevalence of COVID-19 at baseline and endline. Endline is planned for 12 weeks after the intervention begins, but may be shifted according to seroprevalence trends.

Inclusion Criteria:

• Community experiment: Live in selected village
• Individual experiment: Work in selected market

Exclusion Criteria:

• None

We do not plan to share individual participant data with other researchers

The intervention involves wearing a face mask so participants will know if they are in the intervention group. The investigators will be blinded as to intervention assignment.