SAN FRANCISCO, Calif. (KRON) — Football is back and concerts are returning.

Even though large events taking place outside are requiring proof of vaccination and have safety protocols in place, health experts say being outdoors is less risky but with the highly transmissible delta variant — there are precautions to take.

Health experts say the delta variant is more contagious than the virus we were dealing with this past winter and even fully vaccinated people need to be careful in certain situations.

“If you’re stuck in a crowd with people all around you, particularly yelling and screaming like at a concert or football game, I think that’s a risky situation for you and I would try and avoid it right now,” Dr. John Swartzberg said.

U.C. Berkeley Infectious Disease Expert Dr. John Swartzberg says those most at risk are people who are not vaccinated.

Dr. Aruna Subramanian, infectious disease professor at Stanford, agrees.

“If you are doing those activities where you’re close together and you’re shouting, and cheering and singing then you are likely to aerosol it if you have COVID-19 and there is a risk to those around you,” Dr. Subramanian said.

As the delta variant has been described as highly transmissible, large events are still set to happen.

Napa’s BottleRock music festival is requiring proof of vaccination or a negative COVID test.

At Levi’s Stadium where the 49ers will kick off their preseason schedule this weekend, proof of vaccination and a negative COVID test are not required, masks are optional but safety protocols are in place.

This is why health experts caution to be safe.

“We don’t know who is vaccinated and who is not and unfortunately delta variant with the new virus that’s going around even if you’re vaccinated you can have a lot of viral particles in your nasal passages,” Dr. Subramanian said.

“I always carry a mask with me,” Dr. Swartzberg said. “If I’m going out with a walk with my wife, we always just have a mask in our pockets because what if we run into six or seven people that we know and we don’t know if they’re vaccinated or not.”

But there are scenarios considered less risky.

“You can be the only person in a Trader Joe’s and that will be relatively risk-free versus being intimate with somebody outdoors who is unvaccinated,” UCSF Infectious Disease Specialist Dr. Peter Chin-Hong said.

It is suggested to use an N95 mask or double mask if you’re going to be around people at large gatherings.