-- Lets a vaccination (or a program item) repeat indefinitely at a fixed
-- interval — e.g. "ND/IB monthly during laying" — instead of having to be
-- re-added by hand every cycle. Marking a repeating vaccination 'done'
-- auto-creates its next occurrence (see VaccinationController::scheduleNext()).
-- NULL means a one-time dose, same as every row before this existed.

ALTER TABLE vaccinations
  ADD COLUMN repeat_every_days INT UNSIGNED NULL AFTER status;

ALTER TABLE vaccination_program_items
  ADD COLUMN repeat_every_days INT UNSIGNED NULL AFTER age_days;