A re-evaluation of immunisation coverage estimates from the Australian Childhood Immunisation Register.

Immunisation coverage reporting using data from the Australian Childhood Immunisation Register is likely to underestimate immunisation uptake. Since 1997, several initiatives have been introduced to improve both immunisation uptake and notification of immunisation encounters. These initiatives seemed likely to have changed previous coverage estimates. Re-calculation of immunisation coverage estimates for the previously reported cohorts was undertaken. This used current Australian Childhood Immunisation Register data--especially the immunisation history form and the impact of catch-up immunisations--to evaluate delayed reporting. Previous coverage estimates published in Communicable Diseases Intelligence were shown to be at least 2% to 4% below estimates based on data now held by the Australian Childhood Immunisation Register, with greater differences observed in particular jurisdictions.