The Health and Economic Impacts of Group B Streptococcus Disease Among Infants in Ontario, Canada

Group B Streptococcus (GBS) remains a leading cause of neonatal morbidity and mortality worldwide, despite preventive measures such as intrapartum antibiotic prophylaxis (IAP). Globally, an estimated 20 million pregnant individuals are colonized with GBS each year, leading to nearly 400,000 cases of infant GBS disease and over 90,000 infant deaths annually. While routine screening using rectovaginal swabs in the late third trimester and IAP have reduced the incidence of early-onset GBS disease (infection occurring within the first 6 days of life) in high-income countries like Canada, current strategies have important limitations: they are less effective against later-onset GBS disease (beyond the first week of life), may miss cases due to false-negative screening results or changes in maternal colonization status, and have limited impact on GBS-associated preterm births and stillbirths. Moreover, despite the widespread adoption of these prevention strategies in Canada, studies evaluating their effectiveness remain sparse, often relying on outdated or regionally limited data with small sample sizes. Important gaps also exist in fully understanding the true burden of GBS disease, its long-term neurodevelopmental consequences, and its broader economic impact. As maternal immunization with a GBS vaccine is being explored as a potential future prevention strategy, robust epidemiological and health economic data are critically needed to support vaccine development, inform policy decisions, and guide future implementation efforts. This dissertation aimed to address these gaps by evaluating the epidemiological, clinical, and economic burden of infant GBS disease in Ontario, Canada. Leveraging real-world, population-wide health administrative and registry data, this research pursued three key objectives: (1) to estimate the burden of infant GBS disease, describe epidemiological trends, and assess the effectiveness of current prevention strategies; (2) to evaluate the risk of neurodevelopmental impairments (NDIs) in early childhood following infant GBS disease, while examining sex and prematurity as effect modifiers; and (3) to determine the healthcare costs associated with GBS disease in infancy. The findings from this dissertation highlight the substantial health and economic burden of infant GBS disease in Ontario and reveal ongoing challenges with current prevention efforts. In the first study, despite demonstrating high maternal screening coverage, we identified missed opportunities for IAP administration, and the incidence of later-onset disease remained unchanged across the five-year study period. The second study found that survivors of infant GBS disease had approximately twice the risk of developing neurodevelopmental impairments by five years of age, with particularly elevated risks among preterm infants and males. The last study demonstrated that infant GBS disease was associated with substantial short-term healthcare costs, particularly during the first 30 days after disease onset. Collectively, these findings can support clinical and public health planning, inform cost-effectiveness analyses, and contribute to evidence-based policy development as Canada and other jurisdictions explore the potential introduction of maternal GBS vaccination in the future, should a vaccine become available, licensed, and recommended for use.

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