Date of Award

8-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Health Research and Evaluation

Committee Chair/Advisor

Dr. Lior Rennert

Committee Member

Dr. Brian Witrick

Committee Member

Dr. Md Tareq Ferdous Khan

Committee Member

Dr. Md Sakhawat Hossain

Abstract

Respiratory infectious diseases, including COVID-19, influenza, and RSV, pose significant public health challenges, especially during the respiratory virus season. Vaccination remains the primary intervention to mitigate morbidity and mortality associated with these diseases. Vaccine effectiveness (VE) can vary between seasons and populations, necessitating continuous evaluation. This study aims to evaluate the effectiveness of the 2024-2025 COVID-19 mRNA vaccine, 2024-2025 seasonal influenza vaccine, and single-dose RSV vaccine over two seasons.

Utilizing electronic health records (EHRs) from the Prisma Health healthcare system, this dissertation emulated target trials to assess the vaccine effectiveness of each vaccine. Risk set propensity matching was used to get a balanced analytic sample between vaccinated and unvaccinated individuals, and Cox proportional hazards models were used to estimate the hazard ratio (HR) of severe outcomes.

The findings demonstrate that all three vaccines provided meaningful protection against requiring Emergency department (ED) or more severe care, highlighting the role of vaccination in reducing the risk of moderate illness requiring medical care across different viral infections. This is particularly important for public health planning, as lowering ED admissions can significantly reduce healthcare burdens during respiratory virus seasons. However, the study also identified differences in protection against hospitalization. The COVID-19 vaccine showed strong effectiveness in preventing severe outcomes, while the RSV vaccine offered moderate protection, though with some uncertainty. In contrast, the influenza vaccine did not show substantial protection against hospitalization, suggesting it may be less effective in preventing severe cases during the 2024–2025 season.

This study highlights the variable effectiveness of vaccines against respiratory viruses, emphasizing the importance of ongoing evaluation to guide public health interventions. The observed differences in vaccine performance against ED visits and hospitalizations suggest that tailored strategies may be needed to optimize protection, especially for influenza, where the vaccine showed limited effectiveness in preventing severe outcomes during the 2024–2025 season.

Author ORCID Identifier

0009-0007-9905-9510

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