Maybe it was all too good to be true. As COVID-19 case rates fell through the autumn, it seemed as if finally the pandemic was drawing to an end. But then, as it has so many times before, the coronavirus threw another punch. After slow but steady improvement in the public health metrics, the numbers hit a wall.
As of Tuesday this week, the entire Bay Area returned to the Centers for Disease Control and Prevention’s orange “substantial” and red “high” categories of coronavirus transmission.
Truth is, case rates haven’t changed dramatically in recent weeks. Since the beginning of October, several Bay Area counties — including most recently Marin and San Francisco — have bounced between the “moderate,” “substantial” and “high” levels, with case rates zig-zagging across the lines separating the CDC’s official risk levels.
Across the Bay Area and California, cases have been relatively steady since September, data from the state show.
Here’s why the numbers aren’t falling anymore, and what that means for the Bay Area.
Loosening restrictions
One factor keeping case numbers where they are, instead of dropping more, could be the waning use of interventions like masks, according to Dr. Bob Wachter, the chair of UCSF’s Department of Medicine.
Slowly, many Bay Area counties are changing their rules for wearing masks indoors. Last week, for example, Marin county lifted its indoor mask mandate. Alameda, Contra Costa, San Francisco and Sonoma have also eased some rules, allowing fully vaccinated people to go without masks in certain indoor settings including gyms, offices and college classrooms, while masks are still mandatory in shops, restaurants and bars.
Solano county never reinstated an indoor mask mandate after the summer. There, only unvaccinated people are required to wear masks, though they’re encouraged for everyone.
Experts say that the lifting of these restrictions means more cases are inevitable — within tolerable risk levels.
“As long as there’s virus in the population, as we increase our risk behaviors, we will see more infections,” said Dr. Robert Siegel, an immunology expert at Stanford.
Vaccinations
Vaccination rates in the Bay Area are high, and most willing and eligible residents have already gotten their shots. The successful immunization program helps explain why fewer people are getting sick and dying — but also, as vaccination rates top out, why declines in illness are leveling off.
Now, the efficacy of vaccines is showing signs of wearing off for people who got the earliest shots. Many of them are being encouraged to get boosters.
But booster uptake hasn’t been quick, even among eligible populations — which could affect how much of an impact they have on case rates, especially as the holidays approach.
“Our concerns are that uptake hasn’t been matching what we feel is the concern around waning immunity and potential resurgence of COVID in the winter,” said Dr. Naveena Bobba, San Francisco’s deputy health officer. “As we go into the season where we know there are gatherings, we want people to be as healthy and safe as possible.”
“If we fall short on boosters, we’ll see a surge, and we’ll be into yet another bad pattern of surges and remissions,” said Dr. George Rutherford, a professor and epidemiologist at UCSF.
Fortunately, a new cohort of patients has just become newly eligible for shots: 5- to 11-year-old children, whose anticipated inoculations will likely drive vaccination rates in the Bay Area even higher, experts said.
“The availability of the vaccine for 5- to 11-year-old children” makes “high rates of immunity even more achievable,” Dr. Monica Gandhi, an infectious disease expert at UCSF, said.
Added to that, increased uptake of boosters would “mitigate the loss of vaccine efficacy over time,” Wachter wrote in a tweet.
Hospitalizations
The good news is that though cases are plateauing, hospitalizations in the Bay Area continue to trend downwards — a sign that vaccines work, experts say.
Data show that the Bay Area’s per capita hospitalizations due to COVID-19 have stayed lower than the overall California rate since the summer delta surge.
Rutherford pointed out that the Bay Area has also “kept mortality low,” adding that deaths in San Francisco during the 1918 to 1919 pandemic were five times higher than in this pandemic, and the city’s population at the time was much smaller.
“In the Bay Area, we’ve handled this better than anybody,” he said. “We’ve handled this as best we can.”
Danielle Echeverria is a San Francisco Chronicle staff writer. Email: danielle.echeverria@sfchronicle.com Twitter: @DanielleEchev