In general, all doses of the primary series should be with the same product. In the following exceptional situations, a different, age-appropriate COVID-19 vaccine may be administered to complete a primary series at a minimum interval of 28 days from the last COVID-19 vaccine dose. No VAERS report is required: The same vaccine is not available The first dose is unknown A person starts but is unable to complete a primary series with the same COVID-19 vaccine due to a contraindication. For more information, see timing, spacing, and interchangeability of COVID-19 vaccines.