2 major San Francisco hospitals reported that 233 staff members tested positive for COVID-19

• More than 200 hospital staff members tested positive for COVID-19 in July.
• Most of those staff members were vaccinated and presented mild to moderate symptoms.
• The Delta variant has also been known to spread among vaccinated people in breakthrough cases.

Hundreds of staffers at two major hospitals in San Francisco have tested positive for coronavirus in July, with most of them being breakthrough cases of the highly infectious Delta variant, The New York Times reported Saturday evening.

The University of California, San Francisco Medical Center told media outlets that 183 of its 35,000 staffers tested positive. Of those infected, 84% were fully vaccinated, and just two vaccinated staff members required hospitalization for their symptoms.

At Zuckerberg San Francisco General Hospital, at least 50 members out of the total 7,500 hospital staff were infected, with 75-80% of them vaccinated. None of those staffers required hospitalization.

UCSF's chief medical officer, Dr. Lukejohn Day, told The Times the numbers from his hospital showed just how important and effective vaccinations are.

"What we're seeing is very much what the data from the vaccines showed us: You can still get COVID, potentially. But if you do get it, it's not severe at all," Day said.

Day also told ABC7 News that at least 99% of the cases at UCSF were traced back to community spread, but that hospital officials are still investigating and conducting contact tracing.

He added that most of the cases presented mild to moderate symptoms, and some were completely asymptomatic. He said the cases were spread among doctors, nurses, and ancillary staff.

"We sort of are seeing that across the board," he said. "We have so far not detected any patient-to-staff or staff-to-patient transmission right now."

The highly infectious Delta variant has been deemed more transmissible than the viruses that cause the common cold, Ebola, and smallpox, and is equally as contagious as chickenpox, the US Centers for Disease Control and Prevention said in internal documents.

The Delta variant has also been known to spread among vaccinated people in breakthrough cases, prompting the agency this week to recommend that even fully vaccinated people wear masks indoors in areas with high transmission rates.

The CDC emphasized that getting vaccinated is still highly beneficial and is a crucial component to combatting the coronavirus - even the Delta variant.

"Getting vaccinated continues to prevent severe illness, hospitalization, and death, even with Delta," CDC Director Rochelle Walensky told media on Tuesday.