Children who have the vaccination recorded on the health card (H4 = 1).
Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.
Polio 1 vaccination date - year.
If the vaccination date reported is inconsistent with the date of birth or the date of interview or with the dates of other vaccinations part or all of the date of vaccination may be set to 97 "Inconsistent."