Kaiser Permanente on Lawrence Expressway in Santa Clara, Calif., on Oct. 6, 2021. (Harika Maddala/ Bay City News)

Nearly 4,000 Kaiser patients may have received slightly less than the recommended dose of their COVID-19 vaccination last fall at Kaiser Permanente’s Walnut Creek Medical Center, the health care provider said Monday.

Kaiser is now contacting roughly 3,900 people who received a Pfizer-BioNTech COVID-19 vaccine dose between Oct. 25 and Dec. 10.

According to Kaiser’s statement, the patients may have received between .01 and .04 milliliters less than the recommended dose of .30 milliliters.

Kaiser and medical experts from the U.S. Centers for Disease Control and Prevention noted that the difference between the administered dose and the recommended dose is negligible and was unlikely to result in reduced protection against COVID.

However, Kaiser said it is offering an additional Pfizer vaccine dose to the affected patients if they request one.

According to the health care provider, the reduced dosage size was the result of miscommunication between staff and was an isolated incident.

“We took immediate steps to confirm that the issue was isolated and promptly retrained staff and validated their understanding of the correct procedure,” Kaiser said. “We are continuously monitoring so this does not happen again.”