Studies suggest that wearing masks can prevent people from spreading coronavirus (CDC 2020). In other words, masks don’t prevent people from getting coronavirus unless everyone else also wears one and follows the usual distancing and sanitation protocols.
A reasonable analogy for a COVID mask is the diesel particulate filter (or DPF) found on heavy-duty transit buses. Simply put, a DPF filters out engine exhaust soot and prevents the kinds of vehicle emissions that make people sick. Of course, soot isn’t the only thing that makes people sick—just as coronavirus isn’t the only bad virus out there. But masks and DPFs make our air cleaner and healthier for everyone around us.