SACRAMENTO (CBS SF/AP) — A mask mandate returned for lawmakers and staff who work in the Capitol building after around nine people — four who had been vaccinated — tested positive for COVID-19 last week.

When the Capitol reopened last month, masks were still required in public places like hallways, committee rooms and legislative chambers. But fully vaccinated lawmakers and staff were allowed to remove their masks while working in their offices.

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That changed this week following the outbreak. The new directive applies not just to the Capitol, but also the Legislative Office Building and lawmakers’ district offices. Unvaccinated lawmakers and staff must also be tested twice per week, according to memos from the state Assembly and Senate.

It appears the outbreak is among employees of the state Assembly, although no official has confirmed all nine cases occurred among those workers.

Debra Galvert, the Assembly’s chief administrative officer, said in a memo last week that seven cases were of people who worked in the same office. Secretary of the Senate Erika Contreras said that chamber doesn’t have any “current cases.”

Last month, with infection rates at record lows, Gov. Gavin Newsom lifted nearly all of the state’s coronavirus restrictions. But public health officials recently warned that the especially-contagious delta variant of the coronavirus has spread rapidly among the unvaccinated population, causing a rise in new cases and hospitalizations.

Los Angeles County public health officials have urged people to resume wearing masks indoors regardless of their vaccination status. Newsom is not now considering a return of a statewide mask mandate or other restrictions.

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“Well, if we continue to get people vaccinated that will be unnecessary,” he said Wednesday. “This is the call to anyone who hasn’t been vaccinated: Get vaccinated. What more evidence do you need?”

Anyone 12 and over is eligible for the vaccine. So far, about 70% of that population in California has received at least one dose.

At the Capitol, four of the nine cases were fully vaccinated people — a much higher percentage of so-called breakthrough cases than the tiny number statewide. Between Jan. 1 and June 30, the state identified 8,699 coronavirus cases among people who are fully vaccinated. That represents 0.043% of the more than 20 million who have received the vaccine.

“Fully vaccinated” means a person is at least two weeks removed from their final dose of the vaccine.

Of those breakthrough cases, at least 652 people were hospitalized — although the Department of Public Health said it was missing hospitalization data in about half the cases. Another 71 people who had been fully vaccinated died, but state health officials said they did not know if the coronavirus was the primary cause of death.

“While COVID-19 vaccines are safe and effective, some cases are still expected in persons who have been vaccinated, as no vaccine is 100% effective,” the Department of Public Health wrote on its website.

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