A retrospective cohort study of childhood immunisation status in northern Sydney

A survey of their children's immunisation status was conducted among mothers of babies from a three-month birth cohort (January to March 1990) in the Northern Sydney Area in 1992. Its aims were to determine the uptake of immunisation in the area, to examine factors associated with immunisation status, and to assess agreement between the parent's reporting of this status and records of councils and general practitioners. Fifty-eight per cent of the questionnaires (1004) were returned. The full immunisation rate was 86 per cent, 14 per cent were partially immunised and only four children had received no immunisations. Between 74 per cent and 82 per cent of vaccinations were on time at two, four and six months; the rate dropped to 21 per cent at 12 months. Logistic regression analysis showed that premature babies are significantly more likely to be fully immunised, whereas children who have had a serious childhood illness, those with a single mother, or whose mothers are more highly educated, are significantly less likely to be fully immunised. There was 60 per cent agreement between the parent's report of immunisation status and a subgroup of 197 council and 82 general practitioner records. Although all councils in the Northern Sydney Area have a reminder system, most immunisations were found to be done in general practices (64 per cent), where reminder systems are not common.