Influenza and pertussis vaccination of women during pregnancy in Victoria, 2015–2017

In reply: We thank Kong and colleagues for their interest in our study.1 Our article highlighted the potential effect of influenza vaccination during pregnancy in reducing risk of pre‐term birth, as suggested by increased odds of vaccination among women birthing at 37 weeks or later compared with those birthing earlier than 28 weeks' gestation.1 We agree that one explanation of these results may be the potential protective effect that influenza vaccination during pregnancy has on pre‐term birth. This protective effect of influenza vaccines against a range of adverse birth outcomes has been noted in other studies.2 An alternative explanation, however, may be reverse causation, whereby women with longer periods of gestation (≥ 37 weeks) have an increased opportunity to be vaccinated. In this study, data on the timing of vaccination were not available, but we are in the process of making a submission to the data custodians of the Victorian Perinatal Data Collection to enable capture and examination of these data.

We agree that the protective effect of vaccines against pre‐term birth, as well as maternal and infant influenza infection, is an important motivating factor in a woman's decision to vaccinate. In addition, and to improve vaccination coverage for both influenza and pertussis vaccines, all health care workers need to actively promote vaccination for pregnant women in their care, and systems are required at all points of antenatal care to facilitate easy access to vaccines. To this end, broadening the window for pertussis vaccination, which in Australia is now recommended to be given from 20 weeks' gestation,3 may facilitate improved coverage for both vaccines.