COVID: Delta variant now dominant in California, US. Who should worry?
News comes as Pfizer plans to ask FDA to authorize booster shot
The highly contagious Delta is now the dominant variant of the coronavirus in both California and across the U.S., hitting areas with low vaccination rates particularly hard and sparking concerns about what comes next in a pandemic that has dragged on for well over a year.
The news came Thursday as Pfizer reported new evidence that its COVID vaccine was less effective after six months and said it plans to ask the U.S. Federal Drug Administration to authorize a booster shot.
In California, the Delta variant made up nearly 43% of cases the state analyzed in June, ahead of the 30.6% of cases linked to the next most common strain, the UK or Alpha variant, according to the California Department of Public Health. In May, Delta accounted for just 5.8% of cases analyzed in California.
Across the U.S. as a whole, according to the Centers for Disease Control and Prevention, the Delta variant now accounts for 51.7% of new cases. In certain regions, including parts of the Midwest, it makes up north of 80% of cases.
“We’re seeing these variants compete with each other for survival,” said John Swartzberg, an infectious disease expert and professor emeritus at UC Berkeley. “Internecine warfare, and Delta is clearly surviving.”
Health experts have warned that the strain, initially found in India, is more infectious than others and likely increases the chance of hospitalization. And while the vaccines have shown to be highly effective at preventing hospitalization and serious illness, including when it comes to Delta, the strain does appear to be somewhat more vaccine resistant than its predecessors.
New data from Israel showed the effectiveness of Pfizer’s two-dose vaccine in people inoculated in January or February dipped to 64% in preventing infection and symptomatic disease.
But the unvaccinated are truly at risk, officials warned Thursday at a White House briefing.
“Virtually all COVID-19 hospitalizations and deaths in the United States are now occurring among unvaccinated individuals,” said Jeff Zients, the White House COVID-19 Response Coordinator.
Sixty percent of Californians 12 and older are now fully vaccinated, with another 9.4% partially vaccinated. A study published Thursday in Nature found that while people who are fully vaccinated are well protected, people with just one dose are still at risk.
That risk varies by location. Across the Bay Area, vaccination rates are high, and new case numbers remain low, meaning that even people who can’t be vaccinated yet — such as young children — face a lower risk because most of the people around them are inoculated.
“I feel like I’m sitting in this island right now that is probably the best place to be sitting in the world,” Swartzberg said of the Bay Area. “In communities that have lower vaccination rates like the Central Valley or way northern California, those are the areas that will still have more problems with Delta.”
But vulnerable populations in the Bay Area are not immune. An outbreak of the Delta variant at a homeless shelter in Santa Rosa has infected at least 27 shelter residents, with dozens of tests still outstanding. The majority, the city said in a statement, had not been vaccinated.
A recent outbreak of the virus at the state capitol in Sacramento among nine people, including four who were fully vaccinated, combined with growing concerns about the Delta variant, prompted officials to mandate that all lawmakers and staffers wear masks regardless of their vaccination status. In late June, Los Angeles County public health workers cited the Delta variant when they asked even vaccinated people to continue to wear masks in restaurants, grocery stores and other indoor places.
To keep spreading, viruses constantly mutate, and California is now tracking six “variants of interest” and four more-troubling “variants of concern.”
The state’s first known dominant variant — the B.1.427 and B.1.429 strains known as Epsilon — was first detected in California. It was taken over in March by the more-transmissible Alpha (B.1.1.7) variant, from the United Kingdom, which gave way to Delta (B.1.617.2) last month.
“Delta is ultimately going to get replaced with something else if we don’t do something differently,” Swartzberg said. “This is the record that will keep playing over and over again and the only way to stop this is to get enough people vaccinated so the virus can’t find people to multiply in.”
Still, infectious disease experts say it’s important not to panic and to be clear about new cases. While fully vaccinated people can be infected, few will be symptomatic, and a tiny fraction will require any kind of professional medical care.
“Let’s be perfectly clear,” Monica Gandhi, an infectious disease doctor at UCSF, said on Twitter recently, Delta “is not spreading like wildfire across the U.S. This strain is spreading in highly unvaccinated regions without natural immunity.”
California is even likely at or approaching herd immunity — an imprecise marker — among some sectors of the population, particularly among seniors who were among the first to get access to the vaccines.
According to an analysis by George Lemp, an epidemiologist and former director of the HIV/AIDS Research Program at the University of California Office of the President, new cases reported per day in California among people 80 and up have declined more than threefold during the three weeks from June 10-30 compared to late May and early June. Most new cases are among people younger than 35, who are less likely than seniors to be vaccinated.
“These trends show that we are now at herd immunity among persons 65 years and older in California,” Lemp said, “given the high vaccination rates and the substantial declines in cases and deaths observed among these age groups.”