When comparing vaccines in VAERS, keep these critical factors in mind:
Doses administered vary enormously. COVID-19 vaccines have hundreds of millions of doses vs. thousands for rare-disease vaccines. Raw report counts cannot be directly compared. See our denominator problem analysis.
Reporting rates differ by era. Post-2020 vaccines have much higher reporting rates due to stimulated reporting.
Patient populations differ. Some vaccines are given to infants, others to elderly adults. Age alone affects outcome severity.