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.
A small number of companies dominate VAERS reporting. The top 5 manufacturers account for 77% of all reports — but this tells us more about market share than safety.
VAERS tracks reports from 47 manufacturers, but the market is heavily concentrated. The top manufacturer, Pfizer / BioNTech, alone accounts for 559,257 reports (21.2%).
This concentration is almost entirely driven by COVID-19 vaccines. Pfizer-BioNTech and Moderna together produced the vast majority of the 670+ million COVID-19 doses administered in the U.S., so their dominance in VAERS reports is a direct reflection of their market presence.
Before the pandemic, companies like Merck, GlaxoSmithKline, and Sanofi Pasteur dominated the vaccine market with products covering childhood immunizations, flu vaccines, and travel vaccines. Their VAERS report counts are substantial but dwarfed by the COVID-19 era surge.
High report counts for a manufacturer primarily reflect how many doses they've distributed. A company with 50% market share would be expected to have roughly 50% of reports, all else being equal. Comparing manufacturers on raw report counts without adjusting for doses administered is misleading.