Using multiple record-keeping systems (e.g., vaccination record cards, immunization information systems, electronic medical records, Homeless Management Information Systems) will help to ensure that vaccinations are recorded accurately and that people who receive vaccines that require multiple doses will receive the correct vaccine at the correct time. If a person arrives for a subsequent dose of COVID-19 vaccine and does not have their vaccination record card, review the immunization information system and other record-keeping systems for documentation. COVID-19 vaccines are not meant to be interchangeable. Every effort should be made to determine which vaccine product was received as the first dose in order to ensure successful completion of the vaccination series. In exceptional situations in which the vaccine product given for the first dose cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the mRNA COVID-19 vaccination series. For more information about the interchangeability of vaccine products, see Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States.