Is This Vaccine Dose Valid? Minimum Interval and Grace Period (CDC)
Whether a vaccine dose counts under CDC's minimum age and interval rule.
Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Date of the dose being checked
- 2026-01-24
- Kind of vaccine
- Not live, or a live oral vaccine (Ty21a typhoid, rotavirus)
- Grace period rule
- The 4-day grace period applies
- Date of the previous dose
- 2026-01-01
- Minimum interval from the previous dose
- 4
- Unit of the minimum interval
- weeks
Result: Not a valid dose: minimum interval.
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Date of the dose being checked (YYYY-MM-DD)
- Kind of vaccine
- Grace period rule
- Date of the previous dose (YYYY-MM-DD)
- Minimum interval from the previous dose
- Unit of the minimum interval
- Date of birth (YYYY-MM-DD)
- Minimum age for this dose
The other 4 fields
- Unit of the minimum age
- Date of the most recent other live injectable or intranasal vaccine (YYYY-MM-DD)
- Previous dose given the same day as a different live vaccine
- A special grace period the schedule gives this dose
How this is calculated
Citation
CDC. ACIP General Best Practice Guidelines for Immunization: Timing and Spacing of Immunobiologics. Doses 4 or fewer days before the minimum interval or age are valid; 5 or more days early are repeated; two live injectable or intranasal vaccines are spaced 28 days. No schedule is reproduced. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.