People who received a new COVID-19 vaccine booster were more likely to contract COVID-19 than people who received no COVID-19 vaccine doses, according to a new study of prisons in California.

Researchers analyzed data from 33 state prisons from January to July 2023 to try to assess the effectiveness of the bivalent shots, which were introduced in the fall of 2022.

Among 96,201 inmates with data on COVID-19 testing and vaccination, researchers identified 2,835 cases.

They found that 1,187 of the cases were among people who had received a bivalent vaccine, versus just 568 cases among the unvaccinated.