None of the eight states that reported rates of compliance with mask mandates of 75% or higher during summer and early fall 2020 experienced high numbers of infections through the end of October, the data showed.

Conversely, 14 of 15 states that did not require people to wear masks in public during the same period had high infection rates then, the researchers said.

The findings provide new evidence in support of mask-wearing as a major factor that contributes to reduced COVID-19 infection rates, according to the researchers.

“This protective effect of mask wearing was evident across four months of the pandemic,” the researchers wrote.

Since the start of the pandemic last March, public health officials, including those with the U.S. Centers for Disease Control and Prevention, have recommended that people wear masks that cover their nose and mouth to limit spread of the coronavirus.

The virus spreads primarily through respiratory droplets — fluid emitted from the nose and mouth while breathing or speaking — and passes from an infected person to others through the air. But masks can limit at least some of this transmission, research indicates.