An additional mRNA vaccine shot is allowed to be provided for San Francisco residents who got a single-shot coronavirus vaccine from Johnson & Johnson’s.

Residents can receive booster shots at clinics operated by the city.

City’s health director Dr. Grant Colfax said on Tuesday that Johnson & Johnson’s policy remained unchanged and getting an additional shot is optional.

Currently, it was not recommended by the health department for J&J-vaccinated people to get a supplemental mRNA shot, which was according to the U.S. Centers for Disease Control and Prevention guidelines. But there is no harm in taking it.

“If people received the Johnson & Johnson and are requesting a second shot, we will accommodate them, but our policy has not changed,” Colfax said.

Among those who received a Johnson & Johnson’s vaccine is Mayor London Breed. She said she will not consider a supplemental shot at the moment, heeding to the CDC health experts’ advice.

“If they say I need to do it, I’ll do it,” the mayor said. “But if they don’t say that, I’m not going to do it.”

According to Colfax, no conclusive data regarding the advantages of getting a booster shot of mRNA from Pfizer and Moderna are available yet.

“In consultation with infectious disease experts, we do believe this is safe,” he, however, clarified.

A little more than 7 percent of the 665, 000 fully-vaccinated San Francisco residents have received J&J.

The city will keep posted on the data and stick with the recommendations of the CDC on additional vaccine shots.

“All of these vaccines are incredibly effective,” the doctor said, as reported by San Francisco Chronicle. “J&J is a good vaccine, and we will continue to administer it.”