On January 6, CDC revised Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States. The portion regarding dosing intervals is summarized below:

• Routine Scheduling. Do not schedule people to receive dose #2 earlier than recommended (i.e., 21 days for Pfizer-BioNTech or 28 days for Moderna).
• Inadvertent Early Doses. Dose #2 inadvertently administered as much as 4 days too early (“grace period”) should be considered valid.
• No Maximum Interval. There is no maximum interval between dose #1 and dose #2 for either vaccine. If dose #2 is administered beyond 21 or 28 days, there is no need to restart the series or repeat the dose.
• Errors. Vaccine administration errors should be reported to the Vaccine Adverse Event Reporting System (VAERS).

Visit CDC’s COVID-19 Vaccination: Clinical Considerations gateway page for more information.