The U.S. has no central database for immunizations, The Wall Street Journal reports, and there is no one standard proof for COVID-19 vaccinations. In fact, the COVID vaccination cards are not necessarily uniform, since some states and local authorities are handing out their own cards rather than using the CDC’s version. So this means your vaccination card is the only physical proof that you’ve received your shot or shots at the moment, and you’ll want to take good care of it.