New coronavirus cases have jumped more than 20% in California and the Bay Area since the state’s June 15 reopening – a sign that even as residents embrace a return to normalcy, the virus can still spread among unvaccinated people and will likely linger for months to come.
Statewide, new cases crept up from about 900 on June 15 to nearly 1,100 on June 30, according to seven-day averages of new daily infections. In the Bay Area, cases ticked up from 187 to 225 during the same period, according to Chronicle data.
State and local health officials had predicted a rise in new cases after June 15, when California lifted nearly all pandemic restrictions on public life. Case rates are still considered low, at fewer than 3 new infections per 100,000 people statewide and in the Bay Area. In January, during the worst of the winter surge, there were nearly 100 new cases a day per 100,000 people statewide.
In the Bay Area, the biggest jump in new cases is in Alameda County, which has seen a 55% increase since June 15. New cases are up 22% in San Francisco, 27% in Contra Costa County and 35% in Marin County, according to Chronicle data.
In some counties, though, the number of new cases is relatively small. San Francisco went from averaging 11 cases a day to 13. Marin went from four cases a day to five.
COVID-19 hospitalizations are also increasing statewide and in the Bay Area, but at a slower rate than new cases. The number grew 11% statewide and 9% in the Bay Area from June 15 to 30, according to state data.
Deaths are largely flat statewide and dropping in the Bay Area. There is usually a lag time of several weeks between new cases and hospitalizations and deaths.
The rise in new cases can be attributed to three factors: the reopening, the fact that nearly a third of people eligible to be vaccinated have not received a shot and the spread of the more contagious delta variant, said local health officials and infectious disease experts.
Most of the new cases are among people who have not been vaccinated, including young adults and teenagers, and in areas that have lower vaccination rates, health officials said.
“It’s a good argument that the vaccine is helping to protect residents,” said Dr. Nicholas Moss, health officer for Alameda County. “And people who have not had the opportunity to get vaccinated yet, we strongly encourage to do that.”
In neighboring Contra Costa County, the city of Antioch — which has significantly lower vaccination rates than the county overall — accounted for 25% of new cases over the past two weeks, even though it has just 10% of Contra Costa’s population, said county Health Officer Dr. Chris Farnitano.
Unvaccinated people in Contra Costa are 16 times more likely to get COVID than vaccinated people, according to county data. The COVID vaccines also do a better job of preventing serious symptoms in the handful of vaccinated people who do test positive.
“With the lifting of the business restrictions, more people getting out and doing things, a lot of people not wearing masks, it’s kind of a recipe for increased infections in people who are unvaccinated,” Farnitano said.
Unvaccinated people mingling indoors is especially concerning, now that most venues go by the honor system when it comes to masking, said Dr. George Lemp, a former University of California epidemiologist.
“The problem is because they’ve changed the mask mandate, particularly indoors, there’s no way for proprietors of stores or any other facilities to know whether a person who’s maskless indoors is vaccinated or not,” Lemp said. “The large crowds of people who are unvaccinated who gather together indoors in places like Disneyland and other venues around the state are going to spread coronavirus to each other.”
The Bay Area as a whole has one of the highest vaccination rates in the country, led by San Mateo and and Marin counties, where more than 80% of eligible residents are fully vaccinated. More than 70% of residents are fully vaccinated in Santa Clara, San Francisco and Contra Costa counties. But even in those highly vaccinated counties, there are pockets where vaccination rates are less than 50%.
The spread of the delta variant prompted Los Angeles County health officials to urge even vaccinated people to resume wearing masks in indoor public spaces — one of the pandemic restrictions that the state lifted June 15. Local counties have not issued similar advice, but health officials say the growing number of delta infections could mean that the Bay Area’s already impressive vaccination numbers may have to get even better to check the disease’s spread.
“Delta might be transmissible enough, infectious enough, that you just need to push your vaccination rates a little higher,” said Moss of Alameda County. “A more transmissible virus is more likely to get to those susceptible (unvaccinated) people. And even just a small increase in the ability of the virus to pass from one person to another, when you multiply that over millions of people, you can start to see these changes in the pandemic.”