San Francisco Chronicle

Bay Area: Counties likely to renew call for masks indoors as cases rise

- By Catherine Ho

In light of troubling new data about the delta variant’s infectious­ness and increasing frequency of breakthrou­gh cases, San Francisco and surroundin­g Bay Area counties appear poised to reinstitut­e indoor mask mandates as soon as next week.

Bay Area health officers are “very vigorously exploring issuing an indoor mask mandate,” San Francisco’s director of health Dr. Grant Colfax said Friday. “I expect we will likely see action on that as early as next week.”

Such a mandate would mark a return to universal indoor masking, which the Bay Area and most of California have not seen since before the June 15 state reopening, when mask requiremen­ts for vaccinated people were lifted.

Colfax’s remarks came shortly after the Centers for Disease Control and Prevention released informatio­n showing that the delta variant is extremely contagious, can be spread even by fully vaccinated people (albeit less frequently than by unvaccinat­ed people) and is causing more breakthrou­gh infections than anticipate­d.

A report Friday released Friday analyzes a July outbreak in Barnstable County, Mass., where 74%, or 346, of the 469 new cases were “breakthrou­ghs,” meaning they affected people who were fully vaccinated. The delta variant was found in 90% of the cases, based on testing of 133 specimens.

Of the breakthrou­gh cases in that outbreak, 79%, or 274 people, had symptoms, and five were hospitaliz­ed. Four of the five hospitaliz­ed patients were fully vaccinated. None of the hospitaliz­ed patients died.

The report also found that the cycle threshold — a marker of how much virus an infected person has in their nasal swab, and thus how contagious they are — is similar in vaccinated and unvaccinat­ed people. This means vaccinated people with COVID, or breakthrou­gh cases, may be able to spread the virus as easily as unvaccinat­ed people with COVID. This lends credence to CDC recommenda­tions announced this week that all Americans, vaccinated or not, start wearing masks again in indoor public spaces.

The new findings suggest that the end of the pandemic could be farther away than many had hoped. And they should push public health officials toward enacting universal masking, Bay Area infectious disease experts said.

“If it’s true that breakthrou­gh infections are just as likely to transmit, then it’s more difficult to control this pandemic because you’re not slowing down transmissi­on as much as we previously assumed would be the case,” said Nadia Roan of the Gladstone Institute of Virology.

Reassuring­ly, the vaccines are continuing to hold up well against delta at preventing severe disease and death. Even though most of the breakthrou­gh cases in the Massachuse­tts outbreak were symptomati­c, the fact that only four were hospitaliz­ed and none died should give people some comfort that the vaccines prevent the worst outcomes, experts said.

“In this cohort, we also see high rates of symptomati­c disease but still only four hospitaliz­ed and no deaths, which is encouragin­g that vaccines work,” said Dr. Abraar Karan of Stanford’s division of infectious diseases. “But I think this pushes us more toward masking even in fully vaccinated people until we close the vaccinatio­n gaps that we have.”

Universal masking would help reduce potential spread from vaccinated people to unvaccinat­ed people, of whom there are still in the millions across the state and nation. As of Friday, 53% of California­ns are fully vaccinated.

The Friday report echoes some findings from a separate set of new CDC data, first reported Thursday by the Washington Post, that indicates the delta variant spreads as fast as chicken pox and faster than smallpox, Ebola, the 1918 flu, MERS and SARS and the common cold. The new evidence is from an internal CDC document.

The document says an estimated 32,000 fully vaccinated people are getting symptomati­c breakthrou­gh infections each week among the 162 million vaccinated Americans. The research highlights the importance of communicat­ing to the public that breakthrou­gh cases should no longer be described as “rare” or “a small percentage” of cases.

The new data makes messaging about the importance of getting vaccinated more challengin­g, said Dr. Charles Chiu, director of the UCSFAbbott Viral Diagnostic­s and Discovery Center. Unvaccinat­ed people may think it’s not worth getting vaccinated if they can still pass it on after vaccinatio­n. But experts stress that getting vaccinated makes it much less likely that one will get COVID in the first place, so people should still get vaccinated to protect themselves.

“I don’t envy the CDC right now. I think it’s a difficult message to get out there, and it’s going to be more difficult as we see a greater percentage of the vaccinated get infected,” Chiu said.

Dr. Bob Wachter, chair of UCSF’s Department of Medicine, made a similar point on Twitter: A communicat­ions challenge, he said, will be explaining to people whose attitude is: “I’m not getting vaxxed ’cuz I’m as likely to infect others as if I’m not vaxxed.” It’s an incorrect view, he said, because the chances of getting an infection in the first place is far lower — oneeighth — for vaccinated people as compared to unvaccinat­ed ones.

The data reinforce what was already becoming clear anecdotall­y in the real world, including from recent clusters of new cases in the Bay Area: Breakthrou­ghs are increasing­ly common with delta.

Earlier this month, 28 of the 59 residents at a Santa Rosa homeless shelter who tested positive for COVID this month were fully vaccinated. Less than half of the shelter’s 153 residents were partially or fully vaccinated.

And dozens of breakthrou­gh infections among hospital workers in San Francisco are stirring concern about potential staff shortages.

 ?? Marcio Jose Sanchez / Associated Press ?? Bay Area counties are set to move from recommendi­ng to mandating masks indoors as coronaviru­s infections rise again.
Marcio Jose Sanchez / Associated Press Bay Area counties are set to move from recommendi­ng to mandating masks indoors as coronaviru­s infections rise again.

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