At the start of the vaccine rollout in December, experts — including COVID-19 czar Dr. Anthony Fauci — said the United States would see an end to the pandemic when a significant portion of the population has received a shot and the population reaches herd immunity.
Now, some experts are saying the country may never reach herd immunity. A widely circulated story in the New York Times on Monday said more virulent variants and vaccine hesitancy are keeping the goal out of reach.
But while many states across the country face surges and vaccine refusal, California is in a good spot with the lowest-case rate in the country — and a population that mostly wants the vaccine. Hard-hit Los Angeles County reported no deaths from COVID-19 on Sunday, the first time in 410 days the county has not reported at least one fatality.
Could the Golden State — and specifically the Bay Area — reach herd immunity ahead of the rest of the country?
Nobody knows for certain, but local experts are hopeful California is heading toward herd immunity or at least a point where transmission rates will be extremely low soon.
"I think we will get there before the rest of the U.S.," said Dr. George Rutherford, a professor of epidemiology and the head of the division of infectious diseases and global epidemiology at the UCSF. "I think the rest of the U.S. will catch up to it, or get to a point where transmission will go way, way down."
"There likely will be 'regional herd immunity' long before true 'herd immunity' on a national or global landscape," added Dr. Peter Chin-Hong, a professor in the UCSF Health Division of Infectious Diseases.
Herd immunity is the point where a substantial percentage of the population is immune due to vaccination or prior illness. When it is achieved, the spread of disease from person to person becomes low, and the whole community becomes protected, not only those who are immune.
Nobody knows for certain what the threshold is, but Fauci and many other experts have estimated for months that anywhere from 70% to 85% of the population needs to be inoculated to reach herd immunity.
Chin-Hong explained that when Bay Area communities reach this threshold, many local restrictions will continue to let up and "enable us to aspire to that life we had before 2020."
But while life will become more normal for vaccinated people as activities open up, he said that true herd immunity "will be elusive for several years." This is due to three things: vaccine hesitancy, the continued creation of virus variants, and most of all, the lack of current global vaccine equity.
"Until most of us in all countries can be immunized, there will be too much circulating virus to enable us to party like it is 2019," said Chin-Hong, referring to the spread of the virus and variants through global travel. "Until then, it will be playing a game of catch-up."
While California may have experienced a steep decline in cases, hospitalizations and deaths, nearby states — including Washington and Oregon — are seeing surges among younger residents.
Meanwhile, across the Pacific, India's health care systems are overwhelmed and there's a shortage of medical oxygen. The country saw its deadliest day of the pandemic yet on May 2, with 3,689 fatalities. In India, less than 2% of adults have been fully vaccinated.
In the United States, vaccinations are offering hope: 44% of the population has received at least one COVID-19 vaccine dose, and more than 31% are fully vaccinated, according to data from the Centers for Disease Control and Prevention. In the San Francisco Bay Area, these numbers are even higher. In Marin County, 83% of the population age 16 and over has received at least one dose and 62% have completed a series. San Francisco has seen 72% of adults receive at least one shot, while 49% are fully vaccinated. In Santa Clara, 70% have started a vaccine series, and 43% have completed vaccination.
Dr. Monica Gandhi, a professor of medicine at UCSF, said she thinks California and the Bay Area could get to herd immunity sooner than "we think" and puts the herd immunity threshold at 65% to 70%.
"This is because you just have to look up on the world stage to look at places that have higher vaccination rates than we have and are opening up to more mingling and see where their cases and hospitalization rates fall with increasing vaccination rates," said Gandhi, pointing to a table with data from yesterday from Israel, the U.K. and the United States. "At a 62% first dose vaccination rate, Israel has 74 cases today out of more than 9 million people, which is a rate of less than one per 100,000. In California today, we have 1,512 infections, and in San Francisco we have 17 infections despite ongoing testing and opening up more. We have low rates of deaths from COVID-19, with 0 deaths recorded in LA County. All of this is suggestive that we will get to herd immunity with increasing vaccination rates."
The U.S. Department of Health & Human Services map below shows estimates of the percent of the population in each county that may be vaccine hesitant.
US Department of Health & Human ServicesAbout 30% of Americans on average are reluctant to get vaccinated, but the number is lower in California, with an estimated 10% to 15% of Golden State residents vaccine hesitant, according to data from the U.S. Health and Human Services Department. Studies have shown that people who identify as Republican are less likely to get vaccinated than Democrats, and vaccine hesitancy in California is generally higher in red counties, according to the department.
Rutherford is hopeful that people who refused the vaccine at first will change their minds.
"As it starts to ratchet up about what you can and can’t do if you’re vaccinated and not vaccinated, I think that will spur people to get vaccinated," he said. "As a vaccination is required to do things such as flying and going to the office, this idea that 'I just don’t think I want to' or 'I just want to wait awhile' … that’s going to disappear."
Teenagers are another piece of the puzzle for achieving herd immunity. While transmission of the virus is low among young children who are unlikely to have access to vaccines until 2020, teenagers spread the virus like adults and vaccinating them is crucial, experts say.
Vaccinations for that age group are coming soon as the Food and Drug Administration is expected to authorize the Pfizer shot for those age 12 to 15 by early next week, according to the New York Times.
"I think we could see something very close to herd immunity in California this summer if adolescents get vaccines," Rutherford said. "The Bay Area could see herd immunity before California."
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