Local officials have the right to reimplement mitigation strategies to stop the spread of COVID-19 amid a surge in cases fueled by the delta variant, said U.S. Surgeon General Dr. Vivek Murthy.

“Unfortunately we’re seeing rises, particularly among the unvaccinated in many parts of the country now,” Murthy said last weekend.

Approximately 97 percent of COVID-19 hospitalizations in the U.S. are among the unvaccinated and at least 58 percent of current reported cases were directly linked to the delta variant. At the end of May, the variant was estimated to account for just over 3 percent of new cases.

The Centers of Disease Control and Prevention (CDC) has for the last two months said that vaccinated individuals can enter public, indoor spaces without a mask. Amid a surge in cases, Los Angeles County reinstated its indoor mask mandate in all public places for all individuals, regardless of vaccination status and at least 10 additional counties in California, including the city of Berkeley, have highly recommended all residents wear masks indoors again.

“In areas where there are low numbers of vaccinated people, where cases are rising, it’s very reasonable for counties to take more mitigation measures, like the mask rules coming out of LA,” Murthy continued. “And I anticipate that will happen in other parts of the country — and that’s not contradictory to the guidance the CDC issued.”

Los Angeles County Board of Supervisors Chair Hilda L. Solis has said the new mask mandate was not punishment for the vaccinated, but prevention.

“We still have 4 million people out of 10 million that haven’t been vaccinated—and many of them are young people,” Solis said. “And we’re seeing that this transmission is so highly contagious that it will cost more in the long run.”

Murthy reinforced his support for LA County’s decision as an acceptable mitigation approach based on data on the ground. The county reported over 1,000 new COVID-19 cases daily this past week.

“We saw this during the last year of the pandemic, that we have large numbers of people gathering in indoor spaces that is the right setup for COVID-19 to spread,” Murthy said, adding that the CDC will provide surge response teams to assist regions experiencing high coronavirus cases.

Murthy also spoke of the World Health Organization’s warning that the delta variant and three additional variants of concern could prolong the pandemic and possibly lead to the emergence of deadlier strains of COVID-19.

“We’ve made so much progress over this past year, but what I worry about are those that we still have — millions of people in our country who are not vaccinated,” he said.