In October, when COVID-19 cases were declining, Illinois Gov. JB Pritzker said there was a chance the state’s mask mandate could be lifted before the holidays. 

Unfortunately, since that pronouncement cases in Chicago and the state have climbed. On Friday, Nov. 19, Illinois logged 5,720 new cases and Chicago’s average hovered at 514 cases per day. Also on Friday, the Centers for Disease Control and Prevention recommended vaccine booster shots for all adults, an eligibility expansion that was authorized earlier in the day by the Food and Drug Administration. 

In a Tuesday press conference, Dr. Allison Arwady, the city’s chief public health officer, explained that Chicago’s current case count places it in the second highest transmission category — or “high transmission,” defined as 400-799 average daily cases. Dr. Ngozi Ezike, the director of the Illinois Department of Public Health, said in an interview with WBEZ on Tuesday that Illinois is also seeing a rise that she would describe as high transmission.

“Even though we want to be done with COVID, COVID is not done with us,” Ezike said.

Here’s guidance from local public health experts on how to think about COVID safety as the holidays approach.

What’s causing a rise in case numbers right now?

Dr. Emily Landon, the lead epidemiologist with the University of Chicago, said that of the many factors in play the most important is close-range indoor transmission.

“As the weather gets colder, we spend more time indoors,” Landon said. “And that really reduces the amount of ventilation, which makes every interaction that we have with unmasked people a little bit higher risk — or a lot higher risk, really — than what it was when we were outside hanging out with those people.”

Landon thinks of it this way: Add a drop of dye to a bathtub full of water and the effect is diluted and minimized. Add the same drop to a glass of water and you’ll see the color change.

Is it safe to gather during the holidays?

The short answer: Gatherings of fully vaccinated people are far safer than they were last year.

However, four groups still have a higher risk of contracting COVID-19: The eligible yet unvaccinated, children younger than 5 years old, the elderly and the immunocompromised. 

Because large social gatherings can make it difficult to know who’s vaccinated and who’s not, tradeoffs may need to be made. For example, you might want to wear a mask at a holiday party with coworkers or restrict a family celebration to only vaccinated members because eating and drinking would make it impossible to remain masked the entire time.

“What I really want people to think about is how they can make sure … that they are protecting people who are most at risk and that they’re sort of reasonably decreasing the risk of transmission at these events,” Landon said.

The safety recommendation to the unvaccinated or the not-quite-fully vaccinated? Consider staying home.

“If you are not fully vaccinated, you should consider not attending gatherings over the holidays,” said Dr. Candice Robinson with the Chicago Department of Public Health. “But if you plan to do so, we encourage those persons to take a COVID test before gathering as well as masking and social distancing when possible in those settings.”

How do we protect children under the age of 5?

Since children younger than 5 are the only remaining group for whom there is not a developed, approved vaccine, the strategy is to limit their contact to the fully vaccinated only.

But Robinson, of CDPH, acknowledges that there are edge situations. For example, a child with a parent who is immunocompromised may be at higher risk of catching COVID-19 from them. This is because the vaccine offers reduced protection for those adults across a range of conditions such HIV/AIDS, cancer and transplant recipients.

Turning to mitigation factors is the best way to make these encounters safer, including frequent testing, social distancing and wearing masks diligently to reduce the overall risk of transmission for kids and adults alike. Landon, the UChicago epidemiologist, makes the point that masks are most effective when they’re worn by the person who could potentially spread COVID, not the one who could potentially receive it.

“If you want to avoid getting COVID from someone, nurses and doctors and hospitals wear a lot of protective equipment to be up close with unmasked COVID patients. And they get a lot of training on how to do that,” Landon said. “Grandma and grandpa may not have that. And so it’s more important to put a mask on the person who might actually have COVID.”

Landon also offers the common-sense suggestion to set up a separate table where younger kids can eat and drink apart from elderly or immunocompromised individuals.

And how about the elderly or immunocompromised people?

The elderly and the immunocompromised should get booster shots — the sooner the better. 

“The first two doses of the messenger RNA vaccines were extremely effective in everyone, but they’re wearing off a lot faster in older people because their immune systems just aren’t as strong and vigorous as the immune systems in children,” Landon said.

The time frame of two weeks for maximum booster protection ahead of Thanksgiving has already passed, but Landon said getting a shot up to the day before families gather on Nov. 25 will offer benefits. “Because even if they’re then exposed, they’ll have a more robust immune response,” she said.

Otherwise, as with children, the best way to protect the elderly or immunocompromised is to have everyone around them be vaccinated.

What about holiday travel, especially to a place with high case rates?

For the vaccinated, planes, trains and public transportation are “actually pretty safe,” Landon said. All public transportation is federally mandated to have masking in place, and many airlines have implemented vaccine requirements for their employees. 

Landon said she’s more concerned about people traveling to destinations without indoor mask mandates given how frequently people dine indoors while on vacation.

The unvaccinated should consider delaying travel altogether, Robinson said. If travel is necessary, consult the city’s travel advisory, get tested for COVID before and after, and quarantine once back in Chicago. There are currently 38 states and 1 U.S. territory on the advisory. Those locations are averaging a daily COVID case rate of more than 15 people per 100,000 residents for at least two consecutive weeks.

“It’s imperative that people think very, very intently about their plans,” Ezike said. “Just as you would plan a trip and you want to know exactly how you’re going to get there, you have to plan how you’re going to keep yourself safe.”

Are cases expected to go up after Thanksgiving?

Unlike last year, the country now has wide access to effective vaccines, but Landon said potential spikes could happen if “people just throw caution to the wind and go and do all the things that they didn’t do last year.”

“I do think that cases are going to increase as the weather gets colder and we have to do more things indoors,” she said. “And I think that the problem is I don’t know how big that spike is going to be and I don’t know how broad it’s going to be.”

This uncertainty will make planning for the holidays later in the year, like Kwanzaa and Christmas, more difficult. Landon suggests making a plan A — an optimistic agenda that includes everything you want to do — and a scaled back plan B.

“I think if families can make two plans, then it’s much easier to switch,” she said. “If you only make one plan for everybody to get together unmasked for a number of days, staying in the same house, without worrying about the unvaccinated versus the vaccinated and boosters and whatever, then it’s really hard to cancel that.”

Once a booster shot is available to me, is there any reason not to get one?

Unlike previous rounds of vaccine distribution, the booster shots that have been distributed in the U.S. are just for people living here and would not be sent elsewhere, according to Landon at UChicago. In other words, the ethical quandary about receiving vaccinations while other countries around the world struggle with scarcity does not apply to boosters.

“There’s vaccines still expiring on shelves in American pharmacies because people aren’t getting their vaccines, so I think it’s absolutely ethical to get the boosters that you need,” Landon said.

In Illinois, the state’s director of public health said all adults should get a booster shot as soon as possible — even before Friday’s endorsement by the CDC. “Anyone over the age of 18 qualifies to get the booster and we want everyone to be as protected as possible,” Ezike said to WBEZ earlier this week. She said that because Illinois is in the high transmission category, all Illinoisans are living and working in a high-risk setting. Cook County Health officials told WBEZ on Monday that no one seeking a booster would be turned away.

Now that all adults over 18 are eligible, here are the federal guidelines on when to get the booster: Boosters are recommended six months or more after receiving the two-dose Pfizer or Moderna vaccines, or two months or more after receiving the single-shot Johnson & Johnson vaccine.

Katie O’Connell is the morning news editor for WBEZ. Follow her @katieoc.