The San Francisco Department of Public Health is now allowing people who received Johnson & Johnson's single-shot COVID-19 vaccine to get a "supplemental dose" of Pfizer or Moderna's mRNA vaccine, CNBC reported Aug. 3.
The health department decided to allow the extra doses in response to a high number of requests from residents. To receive the second shot, interested J&J vaccine recipients can send a special request to the health department.
In a statement shared with CNBC, city health officials did not refer to the additional shots as "boosters," instead calling them "supplemental" doses.
The public health department is still following CDC guidance, which does not recommend booster doses at this time, officials said.
"This move does not represent a change in policy for [San Francisco Department of Health,]" the department said in a statement. "We continue to align with the Centers for Disease Control and Prevention guidance and do not recommend a booster shot at this time. We will continue to review any new data and adjust our guidance, if necessary."
This comes after research published July 20 in the preprint server bioRxiv suggested J&J's shot was significantly less effective against the delta variant, first detected in India and now the dominant U.S. strain. The same study also found the single-dose shot may be less effective against the lamda variant, first detected in Peru.
At the same time, recent data from J&J showed its shot demonstrated "strong, persistent activity against the rapidly spreading delta variant and other highly prevalent SARS-CoV-2 viral variants."
The company did not immediately respond to CNBC's inquiry regarding the announcement from San Francisco's health department.
In the U.S, studies are underway to determine whether booster doses are needed for the general public, including a National Institutes of Health clinical trial evaluating a mix-and-match approach to COVID-19 vaccine boosters.