The status model
"Is this child fully vaccinated?" sounds like a yes/no question. It is not. greenbook gives two honest answers, and is candid about the messy edges of real records.
Two answers, not one
Every dose due by now has been given.
A perfectly on-schedule 6-month-old is up to date for age - even though MMR and HPV still lie ahead, because those are not due yet. This is the answer a clinician actually wants at a glance.
Values: UpToDateForAge · BehindForAge · Unvaccinated · Unknown
Every dose at every age has been given - the whole schedule, start to finish.
That same on-schedule 6-month-old is not fully vaccinated, and that is the correct answer: they have not had the doses that come later. The strict flag is age-independent.
The headline is what the --format status command distills to a single green/red line. The two must not be confused: a green "up to date for age" does not mean "fully vaccinated".
Honest about messy records
Real records are not tidy. Two cases that naive tools silently hide, greenbook surfaces:
Outside standard schedule
A dose given too early or too late (or too soon after the previous one) is recorded as received but does not count toward completion. It is labelled, not hidden - and not harshly called "invalid". It was a real clinical event; the engine just notes it fell outside the standard rules.
Unmatched dose
A dose whose product class fits no series in the applicable schedule (e.g. a 5-in-1 against the 2026 schedule), or whose code is unknown, is surfaced, not silently dropped. The same 5-in-1 dose conforms under historical versioning when the applicable schedule version asks for a 5-in-1 primary course.
Dose sequencing
When several doses of one product class are recorded, which is dose 1, dose 2, dose 3? greenbook treats date order as authoritative. The recorded dose number (FHIR protocolApplied) and the SNOMED procedure code are cross-checks: if they disagree with date order, the engine raises a soft flag for human review rather than silently trusting the label.
This is what lets a single product class that serves multiple series - MMR → first dose and second dose - be allocated correctly across those series' slots by date, with no spurious "extra dose" or "too early" flags. See the walkthrough for this in action.