The immunization data is included in the KR, BR, and IR files, but the easiest file to use is the KR, which has one record for each child born in the past five years. Age in years is given by b8. Children 12 to 23 months old will have b8=1. The child's age in months is not included in the b variables, but is included as hw1. You could select for months 12 to 23 using hw1 if you wanted. The variables for immunizations are h0 through h9.