The United States has surpassed 500,000 dead in the COVID-19 pandemic, a figure that roughly matches the entire population of Sonoma County. The milestone comes amid steady progress in the Bay Area as vaccinations take hold, Reporter Erin Allday talks about that and new worries about research showing a dangerous variant spreading in California, a mutation that may be both more contagious and more serious. | Unlimited Chronicle access: sfchronicle.com/pod

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