UCSF’s Dr. Bob Wachter on why he’s masking again

COVID-19 cases are rising in California and UCSF’s Dr. Bob Wachter posted on Twitter Monday that he’s returning to more cautious behavior and putting his mask back on in indoor public spaces where they may not be required. 

“In last month, SF has become far less mask-y,” Wachter wrote on Twitter. “At this point, if you’ve decided you’re OK getting Covid (which isn’t crazy if vaxxed/boosted), then fine to keep mask off in crowded indoor spaces. If you’d prefer to avoid Covid & have become less cautious, it’s time to re-think.”

Wachter said he’s covering his face again because he prefers to avoid COVID. He said he’s mostly worried about long COVID symptoms and long-term risks including damage to the heart, neurological impacts and diabetes.

“I’ll now do 100% N95 in crowded indoor spaces,” Wachter wrote. “I’ll strongly favor outdoor to indoor dining, though will eat indoors in small groups (recognizing it’s a risk, but it seems worth it). You should make your own choice, but do it w/ eyes open: there’s a lot of Covid out there.”

Wachter is the chair of the department of medicine at UCSF 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 worldwide.  


After a January peak amid the omicron surge, San Francisco saw a significant drop in cases and the city eased the health mandate, no longer requiring masking in most indoor public spaces. Cases are going back up—though it’s hard to know by just how much as state and city data is less reliable since there are fewer testing sites and more people are testing at home. Wachter said the asymptomatic test positive rate at UCSF, where patients must get tested before certain procedures or if they’re staying overnight, is a good proxy for community prevalence. He said in the last week, the rate is up three-fold, rising to 3.4%, meaning 1 in 30 people in San Francisco are asymptomatic.

“I’d slipped a bit re: masking in non-crowded spaces, & gotten less careful re: restaurants,” Wachter said. “I’m resuming more cautious behavior.”

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