(NEXSTAR) – Don’t rush to eat indoors at a restaurant just yet, says one infectious disease expert.

Though many counties across the nation are opening indoor dining due to low COVID-19 case loads, Dr. Anne Liu, an infectious disease physician at Stanford University, says eating inside is still not a good idea — even if you’re vaccinated.

“For those that are unvaccinated, it is probably still quite risky to eat indoors at restaurants depending on how they’re set up,” Liu said.

It’s in the details for restaurants: Is the eatery well-ventilated? Does it have good air exchange? Are people seated far apart?

Even if the restaurant meets the above standards, Liu says she’s still “worried” about indoor dining.

“As long as you’re sitting indoors with people, even six feet apart, there can still be viral transmission,” she said.

“There’s only so much that all of these measures can do when people have their masks off.”

Liu said even sitting six feet apart still poses a risk because people take their masks off to eat and drink.

“There have been well-documented incidents of super-spreader situations in bars and restaurants where people are supposed to be six feet apart, but they’re taking off their masks,” she said.

She says “whatever you can do to eat outdoors” is beneficial, though takeout is still the safest option.

Even if you’re vaccinated, dining indoors can still pose risks. Liu is especially concerned about the rise in variants across the U.S. and world that appear to be more resistant to the available vaccines.

“With the variant from South Africa and the one from Brazil, the concerning thing is that the vaccine may be somewhat less effective against those strains,” she said. “There may be some reduction in how amazingly effective the vaccines are against those strains, and we’re seeing them in multiple locations across the U.S.”

Liu said the country is definitely not out of the woods yet with the virus, as case numbers are steadily on the rise in certain parts of the country, potentially due to variants.

She stressed continuing to observe public health measures — masking, social distancing and hand washing — because the only way to slow the creation of new variants is to slow the spread of the virus.

“In an ideal world, we would control the numbers, get everyone vaccinated and the rise of variants would be low,” she said.

In a press conference Monday, CDC Director Rochelle Walensky echoed Liu’s concerns.

Walensky grew emotional as she reflected on her experience treating COVID-19 patients who are alone at the end of their lives.

“We have so much to look forward to, so much promise and potential of where we are and so much reason for hope,” she said. “But right now, I’m scared.”

“I’m going to lose the script, and I’m going to reflect on the recurring feeling I have of impending doom.”

Cases of the virus are up about 10% over the past week from the previous week, to about 60,000 cases per day, with both hospitalizations and deaths ticking up as well, Walensky said. She warned that without immediate action the U.S. could follow European countries into another spike in cases and suffer needless deaths.

“I have to share the truth, and I have to hope and trust you will listen,” she said.

The Associated Press contributed to this report.