San Francisco might have reached herd immunity

San Francisco's average of 13.7 new COVID-19 infections per day "is what herd immunity looks like," Dr. George Rutherford, a professor of epidemiology at the University of California, San Francisco, told The Guardian.

Rutherford is one of several experts who believe San Francisco is the first major U.S. city to achieve the long sought-after goal. "You're going to have single cases, but they're not going to propagate out," he said.

It's not entirely clear what the actual threshold is for herd immunity, but 68 percent of the northern California city's eligible residents are fully vaccinated against COVID-19, and 80 percent have received at least one shot, The Guardian reports. Those numbers are certainly in the neighborhood of scientists' herd immunity estimates, some of which are as high as 90 percent, and when adding the amount of people who have recovered from natural infections, it appears the coronavirus may have a hit a wall in San Francisco.

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The city has some natural advantages, The Guardian notes, including the fact that it has a relatively small population of children (no vaccines have been approved for anyone younger than 12), and it's a compact place, geographically speaking, which "has allowed teams of health workers to go door-to-door to reach" people who may not otherwise have been willing or able to get their shots. Read more at The Guardian.