Thousands of people who visited a mass vaccination site in Oakland, California, on March 1 received the wrong dosage of the Pfizer vaccine, KTVU reported.

An estimated 4,300 people were administered less than the recommended dose while getting a shot at the Oakland Coliseum, two unnamed medical workers told the media outlet.

The optimal vaccine dosage is 0.3-mL of Pfizer but thousands of people received around 0.2 mL, KTVU said.

Due to a problem with the syringes, too little of the COVID-19 vaccine was administered, the media outlet reported.