SAN FRANCISCO – Adam Bergeron is excited to reopen the Balboa Theater, the independent San Francisco cinema that he owns and operates.

He has watched other cinemas in the US take the audience back in front of them. But San Francisco reopened more slowly than other cities. Now the time feels right.

“San Francisco was a role model for getting Covid right, if there is such a thing,” said Bergeron.

“At this point, everyone I know is fully vaccinated. Cases are falling. And we just picked a time that seemed like the right time,” he added. He plans to reopen May 14th with a “Godzilla” marathon.

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San Francisco and its suburbs were cautious and maintained various restrictions while other parts of the country reopened businesses and eased masking mandates. The vaccination rate is now among the highest of any major US city. Two thirds of all adults have received at least one dose.

And as parts of the city open up – some bars in San Francisco have waiting lists to get a table again – experts are showing cautious optimism. The city may see signs of herd immunity.

“This is our moment to leave the pandemic behind,” said Dr. Grant Colfax, San Francisco’s director of health. “It is clear that the vaccines are our way out.”

Herd immunity is about transmission. When not enough people can catch and spread a virus, especially in a community where cases are already low, the virus struggles to find new hosts. Eventually, of course, infections would subside. It’s a simple concept, but it can be elusive and difficult to define – especially at the national level.

However, it may be clearer on site. In the past seven days, San Francisco, which was home to more than 870,000 people, had an average of just 26 new Covid-19 cases per day. Two-thirds of all adults in San Francisco and nearly 60 percent of the larger metropolitan area of ​​4.7 million were vaccinated with at least one dose – one of the highest rates in the United States. The positive test rate is 1.2 percent.

All over San Francisco, there are signs that residents are beginning to relax, at least slightly, their emergency arrangements and be rewarded with vaccinations. Some people go maskless on walks outdoors – a rare sight until recently – while small gatherings such as running and cycling clubs have resumed and yoga and other gym classes have resumed. The main office of the city library reopened for rummaging on Monday, and the city was able to enter California’s “yellow tier” – the least restrictive pandemic – this week.

And there are signs that the city is preparing for a long-term reopening. Kevin Carroll, executive director of the San Francisco Hotel Council, a trading group serving the city’s hospitality industry, said the majority of San Francisco’s 34,000 hotel rooms are expected to be open by the end of May. More downtown offices, including the big tech companies, are about to return. Salesforce, the software company that occupies San Francisco’s tallest skyscraper, is aiming to reopen its headquarters this month, spokeswoman Annie Vincent said.

It is estimated that 70 to 85 percent of a city’s population must be immune to achieve herd immunity, but that number can be a moving target. A better indication is whether the number of cases and hospitalizations in a city is falling to a low level and staying so with few restrictions, said Dr. Monica Gandhi, an infectious disease doctor and professor of medicine at the University of California at San Francisco.

San Francisco has had the advantage of speeding up its vaccination campaign, while cases, hospitalizations, and daily deaths are already relatively low, which is most likely a large part of the city’s success to date. Last winter, when much of the country was grappling with a devastating wave, cases in San Francisco peaked on January 4, with 560 infections reported. For comparison: Los Angeles peaked on December 26th with more than 29,000 new cases.

Vaccines can help bring these numbers down, but how quickly this happens depends largely on the local situation. In places where cases are increasing, scientists have observed a tipping point in vaccinations. After that, hospital admissions and deaths begin to drop dramatically.

“It appeared to be 40 to 50 percent at the first dose rate,” said Gandhi. “After that, things started to decline.”

There are currently 15 people hospitalized in San Francisco for Covid-19, which is roughly less than 2 per 100,000 people. While there isn’t a magic number, Gandhi said it is these types of low hospitalization rates that public health officials monitor to make sure a city is on the right track.

In March 2020, San Francisco became the first city in the country to issue a mandatory housing order in response to the pandemic. And the city has maintained other stringent mitigation practices that have helped the city “hit back three waves,” according to Colfax, San Francisco’s health director.

Colfax also recognized the widespread acceptance of the city’s public health interventions for this advancement.

“That culture and public health support and public health infrastructure are deeply ingrained in San Francisco, largely because of our response to the HIV / AIDS epidemic,” he said. “It’s anchored in our cultural DNA.”

But the real test is likely to come this week when the city starts lifting some of its restrictions.

“The final test when you achieve herd immunity is not to be on lockdown and not having mitigation procedures in place,” Gandhi said. “The way we could tell that we got herd immunity with measles is that people were out and about and mingling and people didn’t get sick and children weren’t hospitalized with severe measles.”

However, herd immunity is not a set target and the threshold can vary depending on a number of factors including population dynamics. Reaching herd immunity also does not automatically guarantee that the coronavirus will simply go away. For example, even though more than 90 percent of the US population has received a measles vaccine, outbreaks can still occur.

Hence, herd immunity should not be viewed as an end goal, said Dr. Julie Parsonnet, Professor of Epidemiology and Population Health at Stanford University.

“It’s not permanent, and just because we’ve achieved herd immunity doesn’t mean there won’t be any cases,” Parsonnet said. “Herd immunity is a good construct for modeling, but not for life.”

There is also a risk of developing a variant of the virus that escapes the protection of vaccines. There is no evidence that this has happened so far, but if it did it could jeopardize the protection that communities have built.

And while pockets of land like San Francisco may already have reached a level of immunity that can lift most major restrictions, it can take the entire country a long time to get there – if it ever does. But that doesn’t mean that the lockdowns will last for years or that life can’t go on.

“If we get to a point where the coronavirus is not making people very sick, we are in good shape,” said Parsonnet. “If we don’t get herd immunity as a nation, we will still protect vulnerable people with vaccines and hopefully not have hospitalizations.”

While San Francisco is the first major US city to appear to have lost control of the pandemic, others are likely not far behind.

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More than 46 percent of people in New York City have received at least one dose of vaccine, and cases, hospitalizations, and deaths are steadily declining. Los Angeles County, considered the epicenter of the U.S. pandemic less than five months ago, saw no new deaths from Covid-19 on Sunday and Monday. 54 percent of residents have received at least one dose of vaccine, and it is among several California counties planning to lift restrictions this week.

In other parts of the country, smaller cities such as Albuquerque, New Mexico; Portland, Maine; and San Diego are seeing similar encouraging progress.

“It is deeply hopeful,” said Gandhi. “The vaccines have put us in a whole new world.”

Denise Chow reported from New York City and David Ingram from San Francisco.