By Betty Yu

SAN FRANCISCO (CBS SF) — San Francisco International Airport was jam-packed once again with holiday travelers Friday, a record number of fliers since the COVID-19 pandemic began, a sign that people are itching to travel again.

The Schlatter family from Morgan Hill was headed to Pennsylvania for the holiday weekend.

READ MORE: COVID Surge: Santa Clara County To Require Its 22,000 Workers To Be Vaccinated

“Grandma’s getting older, so it’s good to there, home, and see her and so we’re just happy for the opportunity,” said Kristi Schlatter. “We’re vaccinated and we’re ready for it, we keep ourselves sanitzed and just count our blessings.”

Brad Wallenberg was flying to San Diego.

“Looking forward to some surfing, some diving, some snorkeling, just catching some waves, going to be a good time,” he said.

He’s one of more than 40,000 travelers who were expected to fly out of SFO Friday, compared with more than 12,000 in 2020.

It’s more than half the number of travelers who departed the airport on this day in 2019.

More travel likely means more cases of COVID-19.

READ MORE: Pedestrian Dies After Getting Hit By Car In San Jose

“I would be surprised if we don’t have an uptick after July 4th,” said UCSF Infectious Disease Expert Dr. Peter Chin-Hong. “There will be a lot more movement of people, not only within our region but people coming in to San Francisco from probably higher risk areas.”

But Dr. Chin-Hong said many parts of the Bay Area have herd immunity, and it’s effective. Still he worries about indoor gatherings with unvaccinated people.

People celebrating this holiday weekend should consider vaccination status, size of the crowd, and whether the event is indoors or outdoors.

“Particularly in a big, crowded indoor area, it may make sense even for vaccinated folks to wear masks, while there are a lot of visitors coming into the area, you just don’t want to deal with getting sick,” he said.

Right now, he says the highly transmissible Delta Variant accounts for a third of the cases in the Bay Area.

Dr. Chin-Hong said if you’re vaccinated, it is very unlikely that you will end up severly ill, hospitalized, or in the hospital if you get infected.

MORE NEWS: PG&E to Face Criminal Charges Over Deadly Zogg Fire in Shasta County

“We’re both vaccinated,” said traveler Amanda Gaudreau Ealderrana. “But the kids are not, because they’re under 12. So I guess we will try to be careful with a mask, but for the infant there’s no mask,” added David He.