Catching up on missed childhood vaccinations
Vaccination schedules assume that life gets in the way. Illness, house moves, the newborn fog, a pandemic, migration between countries - all of these leave children behind on the schedule, and all of them are planned for.
The key principle: doses count, even years later
With very few exceptions, a vaccine dose given at any point still counts. If your child had two of three doses of something as a baby and then missed the third, they usually just need that third dose now - not the whole series again. This is true even if the gap is years.
How a catch-up works
Take whatever record you have to a GP, practice nurse, or clinic. They will compare it against your country's schedule and produce a catch-up plan: which doses are missing, in what order, and with what minimum gaps between them. Several can often be given at one visit. A typical catch-up for a school-age child who missed a fair amount might be two or three visits a month or two apart.
If you have no record at all
If a record genuinely cannot be found, the standard approach is to assume the child is unvaccinated and start an age-appropriate schedule. Getting an 'extra' dose of a vaccine a child turns out to have already had is not harmful.
Arriving from another country
Children moving between countries are a common catch-up scenario. Vaccines given abroad are recognised; the receiving country's clinician fills the gaps against the local schedule. Bring the original record and, if possible, a translation of the vaccine names. Comparing the two schedules ahead of time (this site has a country comparison tool) tells you what is likely to be added - for example a country that gives meningococcal B routinely will offer it if your child's previous country did not.
Priorities if you cannot do everything at once
If cost or access forces choices, clinicians generally prioritise MMR (measles is the most immediately dangerous gap), the diphtheria-tetanus-whooping cough-polio group, and, for the relevant ages, meningococcal and HPV vaccines. But in most countries the routine schedule is free, and the aim is simply to complete it.