If people don't continue to take precautions to keep from becoming infected with the coronavirus on Thanksgiving, there may be bad news when Hanukkah and Christmas arrive, according to Dr. Thomas Balcezak, chief clinical officer for Yale New Haven Health.

"The end of this week is going to be a test for all of us," Balcezak said Monday. Two weeks after Thanksgiving, health professionals will know whether family gatherings helped spread COVID-19, but "we'll have an idea in four or five days," he said.

The way cases are rising, the peak in this second wave likely will hit at the end of December, he said.

The good news is that three vaccines appear to be on the way to approval and distribution. "I think it's a very bright light at the end of a very dark tunnel. We should all be very excited that there are three candidates," Balcezak said. Pfizer, Moderna and AstraZeneca all have reported positive results in clinical trials and the vaccines appear to be "very efficacious," Balcezak said.

Even better, AstraZeneca's vaccine can be stored with normal refrigeration, not the subzero temperatures required for Moderna's and Pfizer's drugs, he said.

While the first vaccines may be available around the end of the year, in the meantime people need to stay vigilant about wearing masks, social distancing and hand-washing, Balcezak said. "As citizens, people also need to be responsible and not have large gatherings in their homes and not have large gatherings with friends," he said.

He said once vaccines are available, "it's going to be complicated but it's not impossible" to vaccinate large numbers of people, noting that hospital flu vaccine campaigns have resulted in nearly 100 percent success.

Balcezak also said people can be confident the vaccines will be safe once they're distributed to the public. "When I'm offered a vaccine, I'm going to gladly take it and I'm going to encourage my family to take it, including my elderly parents," he said. "When it is offered to me I'll take it as soon as possible."

The number of cases has spiked dramatically, with 2,118 new cases on Nov. 9, the most so far, compared with 1,186 on April 14, the highest number recorded during the spring surge, according to state Department of Public Health data. But Balcezak said that may be misleading "because there was less testing in the spring. There probably were more undiagnosed cases in the spring."

Tests were not given to asymptomatic people when the virus first swept through the state, but now are more easily obtained. Health officials have a better idea of the number of positive cases now. "We don't know those numbers for the spring with the same kind of reliability because you really needed to be symptomatic to be tested," Balcezak said.

The better number to watch, he said, is hospitalizations. "The criteria for admission has remained relatively constant," he said. There were 393 COVID-19 patients in the health system's five hospitals Monday, "and that was equivalent to where we were near the end of March," he said.

"We're probably four weeks away from peak," he said. "We're going to peak near the end of December." The previous high was about 800 on April 21.

How people respond to precautions will determine whether "community spread immediately stops or community spread takes off and worsens," he said.

While it's good that more people are being tested, so that those who test positive can self-isolate, there are downsides to testing, as well, Balcezak said. There still are not as many tests available as are needed and they need to be made available to the elderly and people with underlying health conditions.

"Testing is good as long as we don't overwhelm our testing ability," he said. The other potential risk is if people test negative and feel they have "carte blanche to do whatever they want to do."

The incubation period for COVID is up to 14 days, and "if you're in that incubation period, you may not test positive but at some point you'll begin shedding that virus," Balcezak said.

"A negative test does not guarantee you anything," he said. It says "you are not expressing that virus through your nose at that moment. But it doesn't tell you anything about the moment later that day ... or later that week."

Balcezak said the health system has enough personal protective equipment and ventilators to handle another peak, but, he said, "I'm worried about staff. Staff have been in this fight for eight months. They're tired and they're discouraged by this wave."

Even though "we have evidence that the lowest-risk people are the people that work in hospitals," many employees are concerned to be working close to people sick with COVID, he said. Meanwhile, hospitals are short-staffed.

"It's emotionally draining; it's physically draining, and they're tired," Balcezak said. "It's not as if we can print more people. There's a national demand."

Yale New Haven Health's five hospitals had admitted 5,905 COVID-positive patients as of Monday, discharged 4,989 and had 642 deaths, according to the health system.

The current numbers at each hospital were: Yale New Haven Hospital, 212; Bridgeport Hospital, 110; Greenwich Hospital, 24; Lawrence + Memorial Hospital, 35; and Westerly (R.I.) Hospital, 13.

Statewide, there were 875 hospitalized patients, according to Gov. Ned Lamont's office. There have been 106,740 cases in the state so far and 4,871 deaths.