Measles vaccination coverage among five-year-old children: implications for disease elimination in Australia.
OBJECTIVE
To (i) assess under-reporting of measles-mumps-rubella (MMR) vaccinations to the Australian Childhood Immunisation Register (ACIR); (ii) estimate MMR coverage among five-year-old children and the proportion immune to measles infection; (iii) identify factors related to non-uptake of MMR vaccination.


METHODS
We analysed ACIR data for a birth cohort of approximately 64,000 children aged five years. The parents of a sample of 506 children with no ACIR record for the second MMR vaccination (MMR2), due at four years of age, were interviewed by telephone to assess under-reporting to the ACIR and reasons for non-uptake of MMR vaccination.


RESULTS
Parents reported that 22% (n = 111) of the surveyed 506 children had received MMR2 before their fifth birthday, and 42% (n = 214) by approximately 5.5 years of age. After correcting for this level of under-reporting to the ACIR, MMR2 coverage for the entire cohort at five years of age was 52.9% (95% CI 52.3-53.4), and increased to 84.1% (95% CI 83.4-84.8) by approximately 5.5 years of age. This was 4.3% and 8.2%, respectively, higher than ACIR coverage estimates at the two ages. Based on the corrected MMR coverage estimates, 93% of the cohort was immune to measles due to vaccination. The most common parent-reported reason for incomplete vaccination was lack of knowledge about the MMR vaccination schedule.


CONCLUSIONS
Measles elimination in Australia will require continued effort in vaccination coverage and timeliness among pre-school children. School-entry requirements are important for MMR2 uptake. Strategies are needed to improve reporting to the ACIR for more accurate measurement of coverage.
Lawrence
Glenda L
GL
National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, University of Sydney, New South Wales. glendal@chw.edu.au
MacIntyre
C Raina
CR
Hull
Brynley P
BP
McIntyre
Peter B
PB
D001294:Attitude to Health; D001315:Australia; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D017589:Immunization Programs / Q000706:statistics & numerical data*; D007115:Immunization Schedule; D007117:Immunization, Secondary / Q000523:psychology / Q000706:statistics & numerical data; D007407:Interviews as Topic; D008297:Male; D008457:Measles / Q000517:prevention & control*; D008458:Measles Vaccine / Q000627:therapeutic use*; D022542:Measles-Mumps-Rubella Vaccine / Q000627:therapeutic use; D010349:Patient Compliance / Q000706:statistics & numerical data*; D012042:Registries
D008458:Measles Vaccine; D022542:Measles-Mumps-Rubella Vaccine