"We took two steps forward with the vaccines, but we're taking a big step back now," said Stanford's Dr. Yvonne Maldonado, who calls the latest data on the Delta variant "groundbreaking."
RELATED: 3 Bay Area counties may be 1st to mandate masks again; here's why
Dr. Maldonado, a pediatric infectious disease specialist and CDC ACIP committee liaison, says because the Delta variant's virus levels are 1,000 times higher in the body than the original variant, it is twice as infectious.
"Now we know that even with vaccinated people, billions of viruses can be present in your nose in your mouth," she continued, "even if you're vaccinated, it's contagious."
That's why this week, the CDC said that even fully vaccinated people need to put their mask back on indoors in places where transmission rates are substantial or high - which is most of the country.
VIDEO: These 5 Bay Area cities may be 'most at risk' for new COVID-19 infections, data shows
The updated advice in part comes from the 4th of July - Provincetown, Massachusetts outbreak - that has led to at least 882 COVID cases. Nearly three quarters of the cases in fully vaccinated people.
"I think we're going to head to a point soon, where everybody may get this virus or may be at risk for it. And if you're vaccinated, you are going to have few to no symptoms," said Dr. Maldonado.
The Delta variant may also be more deadly. But for vaccinated people, the CDC document says the risk of severe disease or death is reduced by at least 10-fold, which was always the goal of the vaccines.
Dr. Maldonado: "The real risk here, I think, is to people who can't get vaccinated, who are children under 12, and some immuno-compromised people."
Kate Larsen: "Dr. Maldonado, have you adjusted any of your behavior in recent weeks, because of all this news?"
Dr. Maldonado: "I'm still wearing a mask when I go anywhere indoors."
Dr. Maldonado says she always wears a surgical mask at the hospital, but when she un-masks to eat or drink, she distances herself from her colleagues, and so far that has been keeping her safe from the Delta variant in a high risk healthcare setting. In addition to masking, she suggests people think about going back to spending time with fully vaccinated pods of people and avoiding crowds, especially for unvaccinated children.
The CDC is expected publish additional data Friday.
Having trouble loading the tracker above? Click here to open it in a new window. RELATED STORIES & VIDEOS:
- Map shows which counties can, can't reopen under reopening tiers
- Cheat sheet: What you can and can't do after being fully vaccinated
- How to register for a COVID-19 vaccine in every Bay Area county
- Map shows everywhere you can get a COVID-19 test in the Bay Area
- Interactive map shows what's closed and what's reopening in the San Francisco Bay Area
- Data tracker: Coronavirus cases, deaths, hospitalizations in every Bay Area county
- Third stimulus check calculator: See how much you could get
- COVID-19 Diaries: Personal stories of Bay Area residents during pandemic
- Get the latest updates on California EDD, stimulus checks, unemployment benefits
- Coronavirus origin: Where did COVID-19 come from?
- What is a COVID-19 genetic, antigen and antibody test?
- What does COVID-19 do to your body and why does it spread so easily?
- Coronavirus Timeline: Tracking major moments of COVID-19 pandemic in San Francisco Bay Area
- Coronavirus Doctor's Note: Dr. Alok Patel gives his insight into COVID-19 pandemic