A GENERAL-PRACTICE CASE-CONTROL STUDY OF DELAYED IMMUNIZATION IN UNDER 2-YEAR OLD CHILDREN

Aim. To identify social factors which characterise the household of ch ildren with delayed immunisation. Method. The study was done in 15 gen eral practices in the Wellington city region with a case-control desig n where preschool children who were not up to date (cases) for their i mmunisations were compared with children who were up to date (controls ). Results. There were 215 cases where immunisation was delayed among 3723 children at the time of audit in June 1996. Ethnic status was ava ilable from general practice records in 33% of cases and 40% of contro ls. There were more Maori and Pacific Island children among the cases compared to controls (39% versus 21%, odds ratio (OR) = 2.39, 95% conf idence interval (CI) 1.12 - 5.10, p = 0.022. Case sample households co mpared with controls had: (1) more children in the households (mean 2. 27 versus 1.98, p = 0.01); (2) more households with a female as the on ly adult (35% versus 24%, OR = 1.61, 95% CI 1.04 - 2.51, p = 0.034). T here was no difference in the proportions of male only adults (0.02% v ersus 0.01%, p = 0.70); (3) more mothers who were under 30 years of ag e (38% versus 25%, OR = 1.61, 95% CI 1.04 - 2.51, p = 0.034); and more fathers under 30 years of age (20% versus 10%, OR = 2.16, 95% CI 0.97 - 4.84, p = 0.06); (4) fewer mothers who were up to date with their r ecorded cervical smear status (66% versus 83%, OR = 0.69, 95% CI 0.23 - 0.63, p < 0.001); (5) more parents with an active community services card (38% versus 25%, OR 1.82, 95% CI 1.17 - 2.82, p = 0.007); (6) fe wer siblings being immunised (70% versus 94%, OR = 0.14, 95% CI 0.07 - 0.28, p < 0.001). Conclusion. There is a distinct group of New Zealan d children for whom immunisation is delayed. Such children live in hou seholds which can be characterised by various social factors easily ob tainable from general practice records. The identified households coul d be targeted for efficient preventive care by general practices.