What is herd immunity? And did it happen in California? A doctor shares his thoughts on this theory and what it would take for herd immunity to happen in the United States.
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Californians may have developed some herd immunity to coronavirus last year, Stanford team theorizes
By ABC7.com staff
Friday, April 10, 2020 1:28AM
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Stanford researchers are investigating if undetected coronavirus may have hit California last year, helping the state develop an early herd immunity.
LOS ANGELES -- New York state has half the population of California but has experienced 14 times as many deaths from coronavirus.
Experts are looking into several possibilities as to why California hasn't been hit as hard.
The trend has been particularly surprising, experts say, given the state has a large number of people in poverty and homelessness, and saw a substantial amount of travel to and from China last year.
One theory centers around the idea of
herd immunity - the concept that a large percentage of a population has already contracted and become immune to an infection, slowing the rate at which it spreads to others.
MORE: Expert explains how herd immunity could contribute to slowing spread of COVID-19
How does herd immunity work? A UC professor breaks down the concept.
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.
"When you look at other states, it doesn't quite explain completely why California has been more fortunate, especially when it should be the least fortunate," said Victor Davis Hanson, senior fellow with the Hoover Institution at Stanford University.
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.
The state had a significant amount of travel to and from China last year - some 8,000 Chinese visitors a day at California's airports. Wuhan, China is considered the origin point of the novel coronavirus. It first came to public attention there in December 2019, but researchers are looking at whether it had been around much earlier than that.
"Something is going on that we haven't quite found out yet," Hanson said. "When you calculate as well there were people on direct flights, from San Francisco and LAX to Wuhan, ground zero of the outbreak, you'd be naive not to think the California population wasn't exposed."
In addition to the Stanford study, USC and the Los Angeles County Department of Public Health are starting a pilot test for coronavirus antibodies in LA County residents.
MORE: How many coronavirus cases in Southern California? See map by location
The tests of 1,000 adults will take place at six drive-through sites throughout the county.
The goal is to determine how many people in the county were already exposed to COVID-19, to get a more accurate picture of how far the virus has spread beyond the current testing of those who are showing symptoms. The test participants have already been selected and the first tests begin Friday and Saturday.
Outside of the studies, a similar finger-stick serology test is also offered at places like Hollywood Urgent Care. It can tell in minutes if a person has already developed coronavirus antibodies. It's the same kind of test used to examine if a person is immune to chickenpox or measles, for example.
"This test will tell you if you had it or not," said Dr. Morris Kokhab, with UrgentMED. "It's basically like when you check your titer for varicella or MMR."
Knowing who has immunity can help get people back to jobs. But for those without immunity, it could be a while.
Dr. Anthony Fauci with the National Institutes of Health says even with the concept of herd immunity, "Ultimately, the answer is going to be a vaccine."
Fauci says dozens of vaccine makers are in the race of their lives.
Among them is San Diego-based Inovio. The company is looking for 40 volunteers to test a potential vaccine. If it's safe, they hope to test the vaccine on 1 million people by the end of the year.
"In my entire career I have never felt the kind of pressure that we are under at the moment," said Kate Broderick, senior vice president of research and development with the company.
There's a lot riding on it.
Mathematical modeling based on China's outbreak suggests if lockdowns across the globe are completely lifted, a second wave of illness could come flooding back unless a vaccine is found.
