Grant: Project Grant

Uncontrolled asthma during pregnancy can lead to adverse maternal and child health outcomes. Asthma attacks in the late second or third trimester are linked to higher risks of recurrent wheeze and severe asthma in children. Viral infections, including Respiratory Syncytial Virus (RSV), commonly trigger asthma attacks in pregnant individuals. RSV is also a leading cause of infant hospitalization and is associated with recurrent wheeze and asthma onset in children. The new RSV prenatal vaccine (RSVpreF) may reduce asthma-related morbidity in mothers and infants, but its safety and benefits in pregnant people with asthma and their children remain unexplored. The PROMOTE project aims to assess, among mothers with asthma, whether receiving vs. not receiving the vaccine decreases the risk of poor (1) maternal outcomes (asthma exacerbation during pregnancy and postpartum, gestational hypertension), (2a) birth outcomes (preterm birth, small for gestational age), and (2b) infant outcomes (asthma-related physician visits and hospitalizations) in the first 6 months after birth. To do this, we will emulate a series of trials at each gestational week (28-37) occurring with follow-up aligning with the RSV season in the first 2 years post-vaccine UK approval (2024-2026) using the Clinical Practice Research Datalink mother-child data. Pregnant people with asthma carrying until at least 28 weeks and their infants will be included. Follow-up will begin at the start of each trial and will end at the outcome date or delivery for pregnancy or birth outcomes, 42 days post-delivery for maternal morbidity outcomes, and 6 months after birth for postpartum and infant outcomes. We will compare outcomes between vaccinated and unvaccinated mothers with asthma. Findings are expected to demonstrate maternal and infant benefits of the RSVpreF vaccine, potentially increasing uptake, shaping vaccination recommendations, and extending protection earlier in pregnancy for women with asthma in Canada.