Poll: Half in U.S. still not wearing masks when out in public By (0) Though masks are effective in stopping the spread of COVID-19, half of Americans don't wear them when mixing with the public. That's a key takeaway from the ongoing study of more than 6,000 U.S. adults by researchers at the University of Southern California Dornsife Center for Economic and Social Research. Advertisement Even though 83% of American adults view wearing a mask as an effective way to protect themselves from COVID-19, their behavior is inconsistent, and often high-risk, researchers found. Two-thirds of respondents said they were in close contact with people outside their household in early December, but only about 51% said they mostly or always wore a mask at those times.