FAQ: Vaccine Safety

VAERS (Vaccine Adverse Event Reporting System) is a national early warning system co-managed by CDC and FDA:

• Anyone can submit reports — healthcare providers, manufacturers, and the public
• Reports are analyzed for patterns that might indicate safety concerns
• It detects potential signals but does not prove causation
• Reports are publicly accessible and often misunderstood

Important: VAERS reports alone do not mean a vaccine caused the event. Correlation ≠ causation.

Source: CDC About VAERS

When a potential safety signal is detected, investigators use multiple methods:

1. Epidemiological studies: Compare disease rates in vaccinated vs. unvaccinated populations
2. Clinical reviews: Examine medical records and timing of events
3. Biologic plausibility: Determine if a biological mechanism could explain the event
4. Vaccine rechallenge: (Rare) Test if symptoms recur with additional doses

This process has led to vaccine contraindications being identified and added to guidance.

Regulators like the FDA weigh multiple factors:

• Disease severity: Is the disease serious enough to warrant vaccination?
• Vaccine efficacy: How well does the vaccine prevent the disease?
• Known risks: What are the documented adverse events?
• Population benefit: Who stands to benefit most?
• Alternative options: Are there other ways to prevent the disease?

This is why some vaccines are recommended for certain age groups or populations but not others.

Source: FDA Vaccine Approval

Multiple systems work together:

• V-safe: Active surveillance using smartphone text surveys
• Vaccine Safety Datalink (VSD): Rapid cycle analysis of electronic health records
• CISA: Clinical Immunization Safety Assessment network for complex cases
• Manufacturer post-licensure studies: Required ongoing safety studies

Source: CDC Safety Monitoring

Yes. Anyone can submit a VAERS report:

• Go to vaers.hhs.gov
• Click "Report an Adverse Event"
• Provide information about the vaccine, the event, and your contact

Healthcare providers are required to report certain events. You can also contact your doctor to report on your behalf.