Written by: Immunization Action Coalition

The recommended dosing intervals for the 2-dose mRNA COVID-19 vaccines are 21 days for Pfizer-BioNTech’s vaccine and 28 days for Moderna’s. Some vaccination clinics are scheduling dose #2 appointments up to 4 days early (i.e., at 17 days) for Pfizer-BioNTech’s vaccine, and as early as 24 days for Moderna’s. COVID-19 vaccines are not recommended to be administered at shortened intervals.

In general, CDC immunization guidelines allow for a “4-day grace period.” This means that if a vaccine dose is inadvertently administered earlier than the recommended time, then, according to CDC, that dose can still be counted as valid.  However, the 4-day grace period is not recommended to be used as an option when scheduling dose #2 of a vaccine.

For the COVID-19 vaccination program, CDC states, “Do not use the grace period to schedule appointments for the second dose.” People who schedule appointments and digital scheduling systems should only offer dose #2 scheduling options beginning 21 days (Pfizer-BioNTech) or 28 days (Moderna) after dose #1.


CDC’s guidance on the use of Pfizer-BioNTech COVID-19 Vaccine

CDC’s guidance on the use of Moderna COVID-19 Vaccine

CDC’s “General Best Practice Guidelines for Immunization” (Timing and Spacing of Immunobiologics Same Antigen)