COVID-19 Pandemic: A Comprehensive Meta-Review of Global Impacts, Responses, and Future Preparedness.

INTRODUCTION: The COVID-19 pandemic due to SARS-CoV-2 has initiated historically unparalleled global health, social, and economic impacts. Syntheses of the multivariable interdependent effects on the multiple clinical, immunologic, psychosocial, and health service realms are required to guide current and future public health preparedness and policy. METHODS: A systematic review of a meta-analysis was conducted using the PubMed, Scopus, and Web of Science databases from December 2019 to 2025 to identify observational studies and randomized controlled trials. Quantitative reporting studies of COVID-19 outcomes were included. Random-effects model aggregated effect sizes were estimated and tested for heterogeneity with Cochran's Q, τ2, and I2. Subgroup, moderator, publication bias, sensitivity, and leave-one-out analyses were conducted for exploration and validation. RESULTS: Twenty-four studies were classified into three categories: clinical outcomes (15 studies), immunogenicity (4 studies), and psychosocial/health service outcomes (5 studies). There was no statistically significant pooled effect (effect ratio 0.95, 95% CI: 0.55-1.62) with severe heterogeneity (I2 > 99%). Immunogenicity showed a statistically significant positive effect (pooled estimate 0.77, 95% CI: 0.38-1.16) with high heterogeneity (I2 ~96%). Psychosocial effects were highly heterogeneous with non-significant overall effects (estimate -1.03, 95% CI: -5.74 to 3.69). Sample size was an influential moderator that explained significant between-group heterogeneity. DISCUSSION: The outcomes reveal robust immunogenic vaccine impacts and indeterminate psychosocial and clinical impacts, consistent with the heterogeneity and complexity of COVID-19 effects. Great heterogeneity highlights methodological standardization and cautious interpretation. This present meta-analysis offers key lessons to guide subsequent study design and manufacture of fair health policy and pandemic readiness.