Skip to main content
VaccineWatch
VaccinesSymptomsStatesAnalysisToolsDashboardCompare

VaccineWatch

Transparent access to VAERS data for informed decision-making. We present the data as-is, with appropriate context and disclaimers.

Explore Data

  • Vaccines
  • Symptoms
  • Manufacturers
  • States
  • Dashboard
  • Compare Tool
  • Search

Deep Dives

  • The Denominator Problem
  • Onset Timing
  • Lot Number Analysis
  • COVID Impact
  • Myocarditis
  • Death Reports
  • Interactive Tools
  • All 23 Articles →

Resources

  • About
  • Methodology
  • FAQ
  • Glossary
  • Side Effects Guide
  • Vaccine Schedule
  • Vaccine Safety
  • Safety Timeline
  • Adverse Events
  • Is VAERS Reliable?
  • Report an Event
  • Disclaimer
  • VAERS Official Site ↗

Sister Sites

  • OpenMedicaid
  • OpenFeds
  • OpenSpending
  • OpenMedicare
  • OpenLobby
  • TheDataProject.ai

Data source: VAERS (Vaccine Adverse Event Reporting System)

Data through 2026 · Updated quarterly

Built by TheDataProject.ai · © 2026 VaccineWatch

Important: VAERS accepts reports of adverse events following vaccination. For any given report, there is no certainty that the reported event was caused by the vaccine. Reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. Most reports to VAERS are voluntary, which means they are subject to biases. This data cannot be used to determine if vaccines cause or contribute to adverse events.

⚠️

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.

  1. Home
  2. Symptoms
  3. Underdose

Underdose

12,134 total reports0.1% serious outcomes
Share

Underdose appears in 12,134 VAERS reports across all vaccines. Of these, 3 reports also mentioned death and 6 involved hospitalization. The severity rate (deaths + hospitalizations as a percentage of reports) is 0.1%. The top vaccines associated with this symptom are COVID19, COVID19-2, HEP. Remember: VAERS reports show temporal association, not causation.

12,134
Total Reports
3
Deaths
6
Hospitalizations
0.1
Severity Rate
% serious outcomes

About Underdose Reports

Underdose has been reported 12,134 times in VAERS from 1990 to 2026.

Of these reports, 3 were associated with death (0.02%) and 6 involved hospitalization.

The overall serious outcome rate (death or hospitalization) for reports mentioning Underdose is 0.1%.

Understanding Underdose in VAERS

•Temporal association only: These reports show Underdose occurred after vaccination, not necessarily because of vaccination.
•Background rates matter: Many symptoms occur naturally at baseline rates in the population, unrelated to vaccination.
•Reporting variability: Medical terminology may be used differently by various healthcare providers and over time.
•Investigation needed: High-frequency reports may trigger further epidemiological studies to determine causation.

What This Data Shows

Most Associated Vaccines: The vaccines most frequently mentioned in reports with Underdose. This may reflect usage patterns, not causation.
Severity Patterns: The percentage of reports that involve serious outcomes can help prioritize safety investigations.
Reporting Trends: Changes in reporting frequency over time may reflect increased awareness, media attention, or actual safety signals.

Most Associated Vaccines

1. COVID196,462
2. COVID19-21,806
3. HEP1,108
4. FLU3860
5. HEPA766
6. FLU4498
7. VARZOS318
8. UNK149
9. TDAP137
10. RV5129
View all vaccines →

Detailed Breakdowns

Underdose × COVID19 →Underdose × COVID19-2 →Underdose × HEP →

Quick Facts

Reports:12,134
Deaths:3
Hospitalizations:6
Mortality Rate:0.02%
Severity Rate:0.1%

Related Analysis

Most Common Symptoms Analysis →Serious Outcomes Analysis →When Do Side Effects Start? →Recovery Rates Analysis →

Explore Further

Compare with Other SymptomsRead Symptoms Analysis

Data Source

This data comes from the Vaccine Adverse Event Reporting System (VAERS), jointly managed by CDC and FDA.