Coverage and predictors of influenza and pertussis vaccination during pregnancy: a whole of population-based study

Background: Respiratory infections including influenza and pertussis are associated with significant morbidity and mortality in mothers and newborns. Vaccination during pregnancy against influenza and pertussis is recommended for all women but data on uptake in Australia is limited.Methods: We conducted a retrospective population-based cohort study in Australia's largest state, New South Wales (NSW), using a Perinatal Data Collection (PDC). Data included demographic, pregnancy, and birth details including pertussis and influenza vaccination during pregnancy for all women giving birth between 01 January 2016 and 31 December 2020. We used descriptive statistics to assess uptake of influenza and pertussis vaccination during pregnancy and Poisson loglinear regression to estimate associations between maternal characteristics and vaccine receipt.Results: During 2016-2020, there were 477,776 births (mean maternal age 32.25 years). In 176,255 (36.9%) births the mother received both vaccines; 202,922 (42.5%) influenza and 315,620 (66.1%) pertussis vaccine. From 2016 to 2020, reported coverage increased from 26.7% to 58.7% for influenza and 43.1% to 78.8% for pertussis, respectively. After adjustment, characteristics associated with lower likelihood of receiving influenza and pertussis vaccination included: younger age (<30 years), being born in Australia/New Zealand, from lower socio-economic strata, having previous pregnancies, being later to first antenatal care, utilising the public hospital care model, smoking, having chronic hypertension and BMI > 25 kg/m(2).Conclusions: While reported coverage of both influenza and pertussis vaccine in birthing women in NSW has increased over time, disparities in coverage exist and they highlight areas where evidence-based interventions to improve maternal vaccination could be targeted.