On October 14, 2021, San Mateo County Health made a correction to the vaccination data that has resulted in lowering the total number of San Mateo County vaccinated residents by around 36,000.

During the past month, we have been working through a data discrepancy between what we and the State report about our vaccination reach in the county. We discovered that our process for synthesizing state data for our local reporting was flawed, which has resulted in diminished accuracy of the vaccination information on our dashboards. The root of this is that we were not capturing all the changes in the state vaccination data registry in our daily downloads and reports. Because we were downloading incremental updates that showed new local vaccinations but not demographic updates that included removing duplicates and correcting address data, the net result is a cumulative decrease in the count of vaccinated San Mateo County residents since December 2020. 

Each of the dashboards that display vaccination reach statistics has now been adjusted to reflect the more accurate counts, and our process for downloading the data has been corrected to improve the accuracy of the data we publish daily.