Immunisation timeliness for a birth cohort in Christchurch. Christchurch Immunisation Coordination Study Group.

AIMS

To determine whether New Zealand's goals for immunisation coverage are being met in Christchurch and to assess whether scheduled vaccinations are being delivered in a timely fashion.

METHODS

A cohort of all infants born in Christchurch during June, July and August 1995 were matched with immunisation benefit claim information for the 6-week, 3-month, 5-month and 15-month immunisation events. Those with incomplete reports were traced for amendment or verification of their immunisation status.

RESULTS

The cohort contained 1002 infants. The full complement of scheduled immunisations was delivered to an estimated 95.8% (95% CI: 94.5, 97.2) of infants within the cohort by two years of age. Infants who presented late for their 6-week immunisation visits were significantly more likely to be late for their next visits (chi 2 log rank = 8.2, df = 1, p < 0.01), as were those late for their 3-month visits (chi 2 = 20.9, df = 1, p < 0.01), and their 5-month visits (chi 2 = 52.5, df = 1, p < 0.01). Infants were significantly less likely to receive their full complement of immunisations by two years of age if they presented late for their 6-week (Fisher's exact test, p = 0.01), 3-month (p < 0.01) or 5-month (p = 0.01) immunisation visits.

CONCLUSIONS

The Immunisation 2000 target of 95% full immunisation coverage by two years of age was met by this cohort. However, infants who were late for any immunisation visits were more likely to be late for subsequent visits and incompletely vaccinated by two years of age, compared to those infants who presented on time.