In 2020, there were two big questions: What are my chances of contracting Covid? If I get infected, what are my chances of getting sick, or dying?

“Today those two have been replaced by one: Are you vaccinated?” Dr. Bob Wachter told local Jewish communal professionals and clergy on Wednesday in a Zoominar hosted by the S.F.-based Jewish Community Federation.

That pretty much covers it, he said. “The vaccines are so unbelievably good and unbelievably safe, once you are fully vaccinated it becomes the determinant of both your risk of catching Covid, and how sick you might become.”

The session, which featured a panel discussion and an update by Wachter, a nationally renowned Covid expert and chair of the Department of Medicine at UCSF, was aimed at helping leaders at Bay Area Jewish organizations determine how and when to reopen their institutions for in-person activities.

The questions came at Wachter fast and furiously from the 50 or so attendees.

Can my synagogue plan for indoor Rosh Hashanah services? If so, how many people can we accommodate safely? How far apart do they have to sit? Can they sing? If they sing, do they need to wear masks?

Can we require that people attending our events be vaccinated? If so, how do we check? Should we institute “vaccine passports”? Or does that infringe on individual rights, as well as Jewish sensibilities?

Wachter fielded them all, with one overarching caveat: There are no hard numbers to protect us — 6 feet of physical distancing, for example, is a guideline, not a prophylactic.

“One hundred people in a tight space with no ventilation is very different from 100 people in Moscone Center,” he pointed out.

All we can do, he advised, is consider the best information we have and then ascertain our comfort level with risk.

The good news for Bay Area residents, he said, is that our Covid numbers are among the best in the nation compared with other urban areas. San Francisco has seen 521 deaths from Covid vs. 30,000 in New York and 20,000 in Los Angeles. Even given the greater populations in those cities, he said, if the national death rate paralleled that of San Francisco’s, 350,000 people who died could still be alive.

“San Francisco and the Bay Area are the poster child for how to get the vaccine right,”  he said, chalking that up to behavioral factors: what people choose to do, based on what their political leaders tell them to do. It is not contingent on race or economic status, he said, except regarding access to information about the vaccine and about how to get vaccinated.

If you are not yet vaccinated, this is a dumb time to let down your guard.

In San Francisco, 64 percent of people have received at least one shot, vs. 40 percent nationwide; 42 percent of city residents are fully vaccinated, vs. 24 percent of all Americans.

Ironically, he said, these good numbers hide a sinister fact: This may be the most perilous time of all for those who are not vaccinated, much more dangerous than last year.

First, he said, as vaccinations progress, people are letting down their guard, leading to increasingly risky behaviors. Second, political leaders tend to look at aggregate numbers in their communities, see that Covid infections and deaths are trending down overall, and then respond to pressures to reopen more quickly than might be safe.

Third, the virus has evolved, and the new variants are more infectious and more dangerous. Precautions that kept us safe in the past might prove ineffective against these new strains, Wachter said.

Despite a few thousand breakthrough Covid infections among the 75 million fully vaccinated Americans, the risk of contracting Covid if you are fully vaccinated is “essentially zero,” he said.

“If you are not yet vaccinated, this is a dumb time to let down your guard,” he said bluntly.

To the synagogue director who asked whether communal singing during worship was safe, Wachter said only if you can guarantee that everyone singing has been vaccinated. And even then, they should wear masks.

The same applies to bringing employees back into the workplace. Plastic shields between desks, physical distancing and face masks offer some protection, but the only true measure of safety is making sure workers are fully vaccinated.

“If you have a group of people with unknown vaccination status, the answer is, it’s not safe,” he said. “You’re playing an odds game, and the virus that may be spreading is more dangerous than six months ago.

“All of the time and money you spent on ‘deep cleaning’ is now understood to be worthless. You’d be far better investing in better ventilation and masks.”

Leaders of Jewish organizations shared some of the challenges they have faced as they plan their reopenings.

Sally Flinchbaugh, COO of the Oshman Family JCC in Palo Alto, noted that they have been slowly reopening since last June, and now require that certain staff, particularly those who work with children, be vaccinated.

There has been some resistance, and those who decline to be vaccinated are not kept on staff, she said. At the same time, each case requires “talking one-to-one” with the employee, and “we take those conversations seriously.”

It comes down to separating the science from the emotion, Flinchbaugh said, but both are important when dealing with human beings who have real fears.

Adam Eilath, head of school at the Wornick Jewish Day School in Foster City, said all of the one-on-one conversations are “exhausting” but nevertheless crucial. “Every individual has to be viewed as being in the image of God.”

Several in the Zoominar spoke about conflicted feelings over requiring proof of vaccination, the so-called “vaccine passport” idea, and that for some it brought up images of Jews forced to wear yellow stars during the Nazi era.

“We’ve had conversations about how weird it feels, as a Jewish organization, to require papers,” said David Goldman, executive director of Congregation Emanu-El in San Francisco. “If we do it, we will have to do it carefully. Again it comes back to separating science from emotions.”

A major concern of attendees was protecting children, and for good reason, Wachter said. While children under 12 are less likely to contract the virus, less likely to get sick and less likely to pass it on compared with adults, the group that is most at risk today in America is between the ages of 12 and 16.

They are more like adults in their infection and transmission rates, he said, but cannot yet be vaccinated. Wachter expects a vaccine to be approved for this age group within four to six weeks and then, he urges, “it will be really important to get those kids vaccinated.”

The curve is flattening as more and more Americans get their shots. But 700 people are still dying every day in this country from Covid, he noted, and everyone looking to reopen a school, synagogue or other Jewish institution has to keep that in mind.

Wachter has little patience for people who refuse vaccination and claim it’s their right to do so.

“The decision for someone not to get vaccinations against a potentially fatal illness is no longer a personal decision,” he said. “It’s communal.”