LOS ANGELES (CBSLA) — Hospitals across Southern California are seeing an increase in COVID-19 patients as the more infectious Delta variant spreads.

Tracy Mitchell, president of Mothers In Action, holds a sign advertising a mobile COVID-19 vaccine clinic, in collaboration L.A. County Department of Public Health Friday (Irfan Khan/Los Angeles Times via Getty Images)

Several doctors — from the emergency room to family care and research specialists — all said the key to stopping the pandemic is the vaccines.

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“If you have made your mind up to not get the vaccine, then you really need to practice the isolation protocols,” Dr. Hector Castillo, a family physician with Dignity Health California Hospital, said. “You need to wear your mask wherever you go.”

Castillo contracted COVID-19 in December, at the height of Los Angeles County’s surge. He said he lost colleagues and friends to the disease and now, as more COVID patients come in for treatment, he said the trauma medical staff went through when hospitals were overrun with critical and dying patients was returning.

“I do get [post-traumatic stress disorder],” he said. “I do feel anxious walking down those corridors, because that’s how I felt when I was seeing my patients either suffering or actively dying.”

Doctors and nurses at Cedars-Sinai Medical Center are also very busy, and another surge could once again diminish resources at any hospital.

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“The healthcare system is currently working super, super hard,” Dr. Sam Torbati, an emergency room doctor at Cedars-Sinai, said. “And adding another strain, with another round of COVID, it will be very challenging.”

In an effort to prevent that from happening, L.A. County health officials have announced that an indoor mask requirement will go into effect Saturday at 11:59 p.m. for both unvaccinated and vaccinated people.

CBS News medical contributor Dr. David Agus said there needs to be more education on the safety of the vaccine and a better understanding of how it protects people.

“It is showing us definitively the vaccines are working remarkably well,” he said. “They are preventing infection, hospitalization and death remarkably in the people who are vaccinated.”

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On Friday, L.A. County reported 1,902 newly confirmed COVID-19 cases, a 700% increase in the number of daily cases reported in just one month. There were also six new deaths reported.