While infectious disease experts agree that wearing a face mask indoors reduces the risk of transmitting COVID-19, there are varying opinions about their effectiveness outdoors.

According to NPR, about two dozen states have broad mandates requiring people to wear masks inside and outside according to a MultiState graphic. City officials often have their own regulations about wearing masks in public.

But with increased vaccination, many experts are rethinking broad mandates on the wearing of face coverings outdoors where the risk of transmission is low, according to research.

“Once you get outside, it starts becoming really, really uncommon for the virus to spread,” said Dr. Ashish Jha, a general internist who is the dean of the Brown University School of Public Health. Jha said that the risk of COVID-19 infections outdoors is estimated to be one in 1,000. He added that these rare infections usually occur at large, packed rallies or gatherings.

The expert said that while infections are still evident and variants are emerging, it is critical to adhere to precautions that make sense, such as wearing a mask inside a room or building. But he added that science does not back up wearing a mask outdoors unless you are with a large number of people crowded together for a prolonged period of time, he told NPR.

But other doctors, like Dr. Jay Bhatt, a primary care physician and public health professional in Chicago, remind us that even when outside, “the risk is not zero,” especially with the highly contagious variants appearing in the U.S., according to ABC News.

And Dr. William Schaffner, a noted infectious disease expert at Vanderbilt University, says the “enhanced contagiousness of these variants means, obviously, that we should take greater care. We should be more careful than carefree,” he said, per ABC News.

Experts suggest that when you are out for a walk by yourself or with a household member, it is not necessary to mask up, but keep one handy. You cannot plan for everything so it’s better to be prepared. And, of course, if your local or state government requires mask wearing in public, you need to follow the rules.

If you are attending a large outdoor concert or event, it would be prudent to wear a mask.

“We know that these infections can be transmitted outdoors with large gatherings of people in proximity such as rallies, parties, and concerts,” Bhatt told ABC News. “Even a socially distanced concert or socially distant event, I would mask.”

In areas, such as Michigan, where the virus is surging, wearing a mask outside is recommended, said Dr. John Brownstein, an epidemiologist and professor of medicine at Harvard Medical School.

Schaffner added that we have a long way to go before we reach the level of herd immunity that will allow us to stop wearing masks altogether. He said it is going to be a tough climb to the top “unless we get very, very much increased participation.”

And that means more Americans have got to roll up their sleeves and get vaccinated.

“Supply of vaccine now exceeds demand,” he told ABC News. “We have the vaccine in the refrigerator, waiting for arms to show up and go into. And vaccine in the refrigerator never prevented any disease.”