Provider Determinants of Maternal Influenza and Pertussis Vaccination Uptake in South Australia in a Tertiary Healthcare Setting

<b>Background</b>: In Australia, maternal influenza and pertussis vaccinations have been recommended for every pregnancy since 2010 and 2015, respectively. Aims: This study aimed to determine maternal influenza and pertussis vaccine uptake in South Australia and assess factors associated with vaccine uptake among pregnant women. <b>Methods</b>: This retrospective cohort study collected data from the South Australian Pregnancy Record (SAPR) or other medical records of women who delivered at the Women's and Children's Hospital from 2016 to 2018. <b>Results</b>: Of 2230 complete records, 53.5% received influenza vaccination and 66.5% pertussis vaccination. Maternal vaccine uptake significantly increased from 2016 to 2018: influenza 43.1-61.6%; pertussis 58.7-71.6%. Healthcare provider discussions with pregnant women about maternal vaccines more than doubled the likelihood of influenza (AOR 2.74, 95% CI: 2.21-3.39) and pertussis vaccine uptake (AOR 2.22, 95% CI: 1.77-2.78). Lower vaccine uptake was observed among women attending midwifery clinics (influenza: AOR 0.72, 95% CI: 0.58-0.90; pertussis: AOR 0.67, 95% CI: 0.54-0.84) or private maternity care (influenza: AOR 0.51, 95% CI: 0.34-0.77; pertussis: AOR 0.40, 95% CI: 0.27-0.60). Shared antenatal care increased the uptake of influenza (AOR 1.51, 95% CI: 1.12-2.04) and pertussis (AOR 1.39, 95% CI: 1.00-1.91). Additional adjustment for SAPR versions did not appreciably change the results, although attending private practice was no longer significantly associated with lower vaccine uptake. <b>Conclusions</b>: Maternal vaccine uptake varies depending on the antenatal care provider. This study identifies opportunities to improve vaccination access during pregnancy and emphasizes the need for targeted strategies to address provider-related barriers.