Childhood immunisation: factors associated with failure to complete the recommended schedule by two years of age

This study aimed to determine the immunisation status of preschool-aged children attending formal child-care facilities in north Queensland, and to examine factors associated with failure to be completely immunised by two years of age. Child-care centres and kindergartens within the Cairns City and Mulgrave Shire local government boundaries were selected randomly with probability proportional to size, and 613 children (median age of 47.0 months) were selected randomly from the facilities. Only 60.3 per cent (95 per cent confidence interval (CI) 56.3 to 64.3) of the children were fully immunised by two years of age. Children who had not received any vaccines by three months of age (that is, 'late starters') were less likely to be fully up-to-date at two years of age than children who started on time (odds ratio (OR) 10.3; CI 5.2 to 20.9). Children without a parent-held immunisation record were less likely to be up-to-date at two years of age than those children with a parent-held immunisation record (OR 2.8; CI 1.9 to 4.0). With follow-up of late-starters, and with the simultaneous administration of overdue vaccines with vaccines given in the second year of life, the percentage of children up-to-date at 24 months of age could have increased from 60.3 per cent to 82.3 per cent (CI 79.1 to 85.5). The immunisation coverage rates were inadequate to prevent outbreaks of vaccine-preventable diseases. Innovative strategies will be required if the vaccine coverage rates are to be improved. The parent-held immunisation record is of fundamental importance to all these strategies.