UCSF’s Dr. Bob Wachter explains why he’s masking up again

COVID-19 cases are on the rise in California and UCSF’s Dr. Bob Wachter posted on Twitter on Monday that he will return to a more cautious demeanor and re-wear the mask in indoor public spaces where they may not be required.

“In the last month, SF has become much less masked,” Wachter wrote on Twitter. “At this point, if you’ve decided it’s okay to get covid (which isn’t crazy if you’re vaccinated/reinforced), it’s okay to take your mask off in crowded indoor spaces. If you’d rather avoid covid and have become less cautious, it’s time to rethink.

Wachter said he is wearing a face covering again because he prefers to avoid COVID. He said he is more concerned about the prolonged symptoms of COVID and the long-term risks, including heart damage, neurological impacts and diabetes.

“I will now do 100% N95 in crowded indoor spaces,” Wachter wrote. “I would strongly prefer to dine outdoors or indoors, although I will eat indoors in small groups (recognizing it’s a risk, but it seems worth it). You must make your own choice, but do so with your eyes open – there are many Covid over there.”

Wachter is the chair of the UCSF department of medicine and has been tweeting about COVID-19 for more than two years, sharing regular updates with his views on the state of the pandemic in San Francisco and around the world.


After a January spike amid the omicron surge, San Francisco saw a significant drop in cases and the city eased the health mandate, no longer requiring the wearing of masks in most indoor public spaces. Cases are on the rise again, though it’s hard to know how much less reliable the state and city data are, as there are fewer testing sites and more people are testing at home. Wachter said the asymptomatic test-positive rate at UCSF, where patients are required to be tested before certain procedures or if they stay overnight, is a good indicator of prevalence in the community. She said that in the last week, the rate tripled, reaching 3.4%, which means that 1 in 30 people in San Francisco are asymptomatic.

“I slipped a little bit around wearing masks in non-crowded spaces and became less careful around restaurants,” Wachter said. “I am resuming more cautious behavior.”

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