Economic modeling across four Pacific Island nations reveals that rotavirus, pneumococcal conjugate, and human papillomavirus vaccines provide substantial cost-effectiveness benefits despite slow implementation in middle-income Pacific countries. The study analyzed vaccination programs in Fiji, Samoa, Tonga, and Vanuatu to support policy decisions regarding simultaneous vaccine introduction. Researchers used established cost-effectiveness frameworks to evaluate the economic impact of preventing rotavirus gastroenteritis, pneumococcal diseases including pneumonia and meningitis, and HPV-related cancers. The modeling incorporated country-specific disease burden data, healthcare costs, and vaccine pricing to determine return on investment for each immunization program. Results indicate that all three vaccines meet international cost-effectiveness thresholds, with pneumococcal conjugate vaccine showing particularly strong economic benefits due to prevention of severe respiratory infections in children. The HPV vaccine demonstrated long-term cost savings through cervical cancer prevention. Pacific Island Countries have historically lagged in vaccine adoption compared to higher-income nations, often due to resource constraints and competing health priorities. This comprehensive economic analysis provides evidence-based support for health ministries to prioritize vaccine program expansion, potentially through coordinated regional procurement strategies to reduce costs and improve access across the Pacific region.