Comparative Effectiveness of mRNA and Viral Vector COVID-19 Vaccines in Multicentric Populations

The global rollout of COVID-19 vaccines has relied heavily on two major platforms: messenger RNA (mRNA) vaccines and viral vector vaccines. While both demonstrate efficacy in preventing severe disease and mortality, differences in real-world effectiveness across diverse populations remain underexplored. This multicentric study compares the clinical effectiveness, safety outcomes, and durability of immune responses between mRNA (e.g., BNT162b2, mRNA-1273) and viral vector vaccines (e.g., ChAdOx1 nCoV-19, Ad26.COV2.S) across heterogeneous populations. Data were collected from multiple international cohorts representing varied demographics, comorbidities, and viral variant exposures. Effectiveness was evaluated using incidence rates of breakthrough infections, hospitalization, intensive care unit admissions, and all-cause mortality within a defined follow-up period. Preliminary findings suggest that while mRNA vaccines provided higher protection against symptomatic infection and severe outcomes during the dominance of early variants, viral vector vaccines maintained comparatively stable protection in resource-limited settings with logistic advantages. Both platforms demonstrated robust safety profiles, though adverse event patterns varied by population and vaccine type. Importantly, waning immunity was more pronounced in viral vector recipients, highlighting the need for tailored booster strategies. This study underscores the importance of vaccine platform-specific evaluation in guiding public health policy, resource allocation, and booster dose prioritization in global pandemic response.