Study finds mask mandates, dining out influence spread of coronavirus

NEW YORK — A new national study adds strong evidence that mask mandates can slow the spread of the coronavirus, and that allowing dining at restaurants can increase cases and deaths.

The Centers for Disease Control and Prevention released the study Friday.

“All of this is very consistent,” CDC Director Dr. Rochelle Walensky said during a White House briefing on Friday. “You have decreases in cases and deaths when you wear masks, and you have increases in cases and deaths when you have in-person restaurant dining.”

The study was released just as some states are rescinding mask mandates and restaurant limits. Earlier this week, Texas became the biggest state to lift its mask rule, joining a movement by many governors to loosen COVID-19 restrictions despite pleas from health officials.

“It’s a solid piece of work that makes the case quite strongly that in-person dining is one of the more important things that needs to be handled if you’re going to control the pandemic,” said William Hanage, a Harvard University expert on disease dynamics who was not involved in the study.

The new research builds on smaller CDC studies, including one that found that people in 10 states who became infected in July were more likely to have dined at a restaurant and another that found mask mandates in 10 states were associated with reductions in hospitalizations.

The CDC researchers looked at U.S. counties placed under state-issued mask mandates and at counties that allowed restaurant dining — both indoors and at tables outside. The study looked at data from March through December of last year.

The scientists found that mask mandates were associated with reduced coronavirus transmission, and that improvements in new cases and deaths increased as time went on.

The reductions in growth rates varied from half a percentage point to nearly 2 percentage points. That may sound small, but the large number of people involved means the impact grows with time, experts said.

“Each day that growth rate is going down, the cumulative effect — in terms of cases and deaths — adds up to be quite substantial,” said Gery Guy Jr., a CDC scientist who was the study’s lead author.

Reopening restaurant dining was not followed by a significant increase in cases and deaths in the first 40 days after restrictions were lifted. But after that, there were increases of about 1 percentage point in the growth rate of cases and — later — 2 to 3 percentage points in the growth rate of deaths.