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Important: VAERS reports alone cannot determine if a vaccine caused an adverse event. Reports may contain incomplete, inaccurate, or unverified information. Correlation does not equal causation.

Onset Calculator

Explore when vaccine adverse events typically occur. Select a vaccine to see the timing distribution of VAERS reports and understand onset patterns.

73%

of events within 3 days

Day 0

most common onset day

104

vaccines to explore

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Important Notes

• This tool shows when adverse events are reported, not when they necessarily begin
• Most vaccine side effects occur within the first few days after vaccination
• Timing patterns are similar across different vaccine types
• Not all VAERS reports include precise onset timing information