FDA BEST Program

The FDA's Biologics Effectiveness and Safety (BEST) initiative is the agency's flagship system for active post-market surveillance of biologics, including vaccines. Using large healthcare databases, BEST conducts real-world evidence generation to monitor vaccine safety and effectiveness after regulatory approval.

How BEST Works

BEST leverages data from multiple sources to monitor vaccine safety:

• Claims databases: Medicare, Medicaid, and commercial insurance claims data covering millions of patients
• Electronic health records: Integration with health system EHR data
• Registries: Disease-specific and product-specific registries
• Vaccine administration data: Integration with state immunization information systems
• FDA Adverse Event Reporting System (FAERS): Synergy with passive reporting data

Active vs. Passive Surveillance

BEST represents a shift from passive to active surveillance:

• Active: FDA initiates studies based on specific hypotheses; has denominators and comparison groups
• Comprehensive: Can detect both known and unknown adverse events through broad outcome monitoring
• Quantitative: Can calculate relative risks and attributable risks
• Real-world evidence: Reflects actual use in diverse populations beyond clinical trial settings

Key Findings from BEST

BEST has contributed to several important post-market safety assessments:

• COVID-19 mRNA vaccines: Confirmed myocarditis/pericarditis signal, particularly in young males after second dose
• Shingrix vaccine: Demonstrated acceptable safety profile in older adults
• Fluad (adjuvanted flu vaccine):strong> Monitored for potential increased reactogenicity
• Novel vaccine platforms: Active monitoring of newly licensed vaccines in real-world settings