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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.

Injection site mass

16,666 total reports1.4% serious outcomes

16,666

Total Reports

Deaths

224

Hospitalizations

1.4

Severity Rate

% serious outcomes

About Injection site mass Reports

Injection site mass has been reported 16,666 times in VAERS from 1990 to 2026.

Of these reports, 6 were associated with death (0.04%) and 224 involved hospitalization.

The overall serious outcome rate (death or hospitalization) for reports mentioning Injection site mass is 1.4%.

Understanding Injection site mass in VAERS

•Temporal association only: These reports show Injection site mass 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 Injection site mass. 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.