Despite the maternal and infant health benefits of antenatal vaccines and availability of government-funded vaccination programs, Australia does not have a national system for routinely monitoring antenatal vaccination coverage. We evaluated the potential use of Western Australia's mandatory Midwives Notification System (MNS) as a tool for routinely monitoring antenatal vaccination coverage.
Two hundred and sixty-eight women who gave birth to a live infant between August and October 2016 participated in a telephone survey of vaccines received in their most recent pregnancy. For women who reported receiving influenza and/or pertussis vaccine and whose vaccination status was documented by their vaccine provider, MNS vaccination data were compared with the vaccine provider's record as the 'gold standard'. For women who reported receiving no vaccines, MNS vaccination data were compared with self-reported information.
Influenza and pertussis vaccination status was complete (i.e. documented as either vaccinated or not vaccinated) for 66% and 63% of women, respectively. Sensitivity of MNS influenza vaccination data was 65.7% (95% CI 56.0-74.2%) and specificity was 53.0% (95% CI 42.4-63.4%). Sensitivity of MNS pertussis vaccination data was 62.5% (95% CI 53.3-70.9%) and specificity was 40.4% (95% CI 27.6-54.7%). There was no difference between vaccinated and unvaccinated women in the proportion of MNS records with missing or unknown vaccination information. When considering only MNS records with complete vaccination information, the sensitivity of the MNS influenza vaccination field was 91.8% (95% CI 83.0-96.9%) and the sensitivity of the MNS pertussis vaccination field was 88.0% (95% CI 76.7-95.5%).
Due to the high proportion of records with missing or unknown vaccination status, we observed low sensitivity and specificity of antenatal vaccination data in the MNS. However, given we did not observe differential ascertainment by vaccination status, MNS records with complete information may be reliable data source for routinely monitoring antenatal vaccine coverage.