San Francisco is nearing COVID-19 herd immunity; L.A. isn't - Los Angeles Times

San Francisco is nearing herd immunity, some experts believe, a milestone in California’s efforts to gain control of the COVID-19 pandemic.

San Francisco has one of California’s highest rates of vaccination, with 72% of residents having received at least one dose.

Only one other county in California — Marin, just north of San Francisco — has a higher rate of vaccination, with 75% of residents there at least partially vaccinated.

There is no definitive percentage at which herd immunity to the coronavirus is achieved.

Previous guesses for when herd immunity to the virus is achieved have ranged from 70% to 85% of community members with immunity.

Despite the hazy parameters around reaching herd immunity, getting closer to it by maximizing vaccination rates remains a paramount goal of public health experts.

George Rutherford, who believes north of 75% of a population likely needs to be immune before herd immunity is achieved.

County had achieved herd immunity yet; she is hoping to reach that goal by the end of the summer.

Nothing suddenly happens when herd immunity is achieved — daily coronavirus case rates are already extraordinarily low in San Francisco.

And, technically, herd immunity is achieved gradually: The more people who gain immunity, the slower the rate of disease transmission.

But once herd immunity is achieved, as new coronavirus cases are introduced among unvaccinated people, such as through travelers, they’re unlikely to spread beyond a small outbreak or to start growing exponentially throughout a community.

During the peak of the flu season, hospitalization rates for the flu on average top out at about 20 to 40 per 100,000 residents.