People who are fully vaccinated have a substantially lower risk of becoming severely ill from the delta variant — with the unvaccinated accounting for the vast majority of hospitalizations.
But new data released Friday from the Centers for Disease Control and Prevention indicate that vaccinated people with so-called breakthrough infections — those who contract the virus but generally experience much milder symptoms — can carry the same amount of viral load, and be as contagious, as those who are unvaccinated.
"High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus," CDC Director Dr. Rochelle Walensky said in a statement Friday.
When asked if the spread of the delta variant could prompt Bay Area counties to delay in-person learning for students this fall, local health officials emphasized that keeping kids in classrooms remains a high priority.
"We saw the emotional, mental and social deterioration of many students" when they were attending school remotely, said Dr. Lisa Santora, Marin County deputy public health officer. "Our goal is to get kids in school, and keep them in school."
Officials also said they're looking at ramping up COVID-19 testing options, since demand for testing has rebounded amid the current surge.
In the city of Berkeley, which is in Alameda County but has its own public health department, businesses will be required under the new order to have signs indicating that masks are required indoors, said Lisa Hernandez, the city’s health officer.
San Francisco does not plan to enforce its new order but will rely on the tendency of residents “to follow the science and the data,” said Naveena Bobba, the city’s deputy director of health.
Monday's announcement follows a recent recommendation from the CDC and the California Department of Public Health for everyone to resume wearing masks indoors in public settings.
Most counties in California dropped their indoor mask mandates for vaccinated people when the state reopened on June 15, although some exceptions remain for crowded spaces like public transit, schools and health care settings. But last month, several counties across California — starting with Los Angeles County — began reinstituting those requirements as the delta variant became the dominant strain.
Health officials on Monday also continued imploring unvaccinated people to get the shot immediately, emphasizing that even though the Bay Area has among the highest vaccination rates in the country, a significant percentage of people throughout the region remains unprotected.
The new variant, they added, has thwarted hopes of reaching "herd immunity" anytime soon — referring to when enough people become protected from a virus to significantly diminish its spread.
"Quite frankly, vaccines are keeping thousands out of Bay Area hospitals right now," said Dr. Lisa Hernandez, health officer for the city of Berkeley. "If you are 12 and older we urge you to get vaccinated as soon as possible, it will protect you, those around you, and help keep our region safer."
Unvaccinated Californians can go to myturn.ca.gov or call (833) 422-4255 to schedule their appointment or go to myturn.ca.gov/clinic to find a walk-in clinic in their county.