Californians may have developed herd immunity to coronavirus last year

"Stanford researchers are looking into the possibility that coronavirus first hit California undetected last year, much earlier than anyone realized, and was only seen at that time as a particularly nasty and early flu season.

As a result, the theory says, many Californians have already unknowingly been exposed to the coronavirus and have developed immunity to it.

To investigate that idea, researchers are testing people for antibodies that indicate a previously undiagnosed infection that was defeated by the body's immune system.

The Stanford researchers tested 3,200 volunteers at three testing sites in the Bay Area. They are expected to publish the conclusions of their study in several weeks."