As the pandemic wears on and many people become complacent, Dr. Bob Wachter, UCSF chair of medicine, says he still plans to abstain from indoor dining, and don a mask in crowded rooms.
In a lengthy tweet thread Saturday, Wachter said he’ll return to restaurants only when daily case rates fall below 5 for every 100,000 people in the region. That’s a significant drop from the national rate of 28 cases for every 100,000 people, and even from the more moderate daily case rate in San Francisco, of 19 per 100,000.
“Clearly, many will find my threshold too conservative, others too risky,” tweeted the doctor, who has cultivated a huge social media following since the onset of COVID-19, offering prodigious, data-driven threads about the disease. His posts mix public education with personal stories and opinions: Recently, Wachter compared unmasking to reckless driving.
San Francisco dropped its mask mandates months ago, but the doctor’s string of tweets Saturday said he considered many factors before setting the yardstick for his own unmasking. Chief among them: immune status, which is better for people who are boosted and particularly those boosted recently, or those who have also had COVID. He also took the virus’ contagiousness into account — and said BA.5, which surged this summer, is “the most infectious variant yet.”
Wachter estimates a 5% to 10% chance of getting COVID from moderate exposure to an infected person, say, sitting nearby on an airplane.
Drawing on UCSF’s asymptomatic test positivity rate of 2.9% — or one person testing positive in every 35 people who have no symptoms — Wachter concluded that, in a group of 10 people, at least one will have COVID, 25% of the time.
“That’s too high for me to feel comfy ditching the mask,” Wachter said.
But he ended on a hopeful note. Future variants of COVID are unlikely to be more infectious than BA.5, and “bivalent” COVID vaccine boosters will arrive this fall.
Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan