Written by Christopher Curley on December 14, 2020 — Fact checked by Jennifer Chesak CDC officials want to use personal data to keep track of the effectiveness and side effects of COVID-19 vaccines. Mark Lennihan/Getty Images Officials at the Centers for Disease Control and Prevention (CDC) are asking state and local officials to provide them with personal data on people who get the COVID-19 vaccine. CDC officials want the information to keep track of the effectiveness as well as any side effects of the vaccines. Some experts have expressed concerns over the use of this private health data and said undocumented immigrants might be reluctant to get vaccinated due to the CDC request.