Still far from herd immunity, California could face a 4th COVID-19 wave

California
Brandi Harrapence, right, and daughter Kayla dine indoors at Firestone Grill in San Luis Obispo in this undated photo. The restaurant was open for indoor dining as San Luis Obispo County moved into a less restrictive tier of the state’s reopening plan on March 2021. (Al Seib/Los Angeles Times)

Brandi Harrapence, right, and daughter Kayla dine indoors at Firestone Grill in San Luis Obispo in this undated photo. The restaurant was open for indoor dining as San Luis Obispo County moved into a less restrictive tier of the state’s reopening plan on March 2021. (Al Seib/Los Angeles Times)

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California is optimistic that the worst of the COVID-19 pandemic is in the rearview mirror. But there are a number of things that could still go wrong and prompt a fourth wave, experts warn.

Dr. George Rutherford, an epidemiologist and infectious diseases expert at UC San Francisco, estimated that roughly 67% of a population needs immunity to COVID-19 before herd immunity can be established, meaning the spread of disease between people is unlikely.

It’s not a hard-and-fast percentage, Rutherford said; the threshold given by the U.S. government’s top infectious diseases expert, Dr. Anthony Fauci, is around 70% to 85%.

Nationally, about 40% of people are believed to have immunity to COVID-19, Rutherford said, either from vaccination or because they’ve been previously infected and have survived. About 26% to 39% of California’s population is probably immune — a figure lower than the national average “because we haven’t had so much infection and, as a result, have not had as much naturally acquired immunity,” Rutherford said last week at a campus forum.

Read the full story on LATimes.com.

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