What the Green Book is
The Green Book - Immunisation against infectious disease - is the UK's definitive guidance on vaccines and vaccination. Chapter 11 carries the routine childhood immunisation schedule: which vaccines a child should receive, and at what ages.
It is published by UKHSA as human-readable PDFs on GOV.UK. For a clinician, that is exactly right. For a computer, it is a problem.
The "digital paper" problem
As of 2026 there is no computable version of the schedule. The PDF is the source of truth. So every digital system that needs the schedule - GP systems, child health information services, the NHS App - re-implements it by hand from the PDF:
Word document → PDF on GOV.UK → Hand-written code in each vendor's system
Each vendor reverse-engineers the rules into code. That derivative is lossy and error-prone, and - because there is no shared machine-readable original - the implementations diverge, drift, and break independently. We call this digital paper: a document that looks structured but carries no structure a machine can trust.
"Is this child fully vaccinated?"
The question the schedule exists to answer turns out to be deceptively hard. To answer it you have to know three separate things:
- Which schedule applied when the child was born - and what was in scope by the time each dose was due.
- What they actually received - the recorded doses, often from several systems.
- Whether what they received satisfies the schedule that applied to them.
And "fully vaccinated" does not even mean one thing - see the status model. A perfectly on-track 6-month-old has not had MMR yet (it is not due until 12 months); calling them "not fully vaccinated" is technically true but clinically misleading. The honest headline is up to date for age.