Underreporting factor. For mortality based on CMS data that came through the whistleblower lawsuit to the FDA found a factor of 5.
The paper from Pantazatos (COVID vaccination and age-stratified all-cause mortality risk, 2021), found a factor of 20.
Prior to COVID, Harvard established, according to review of real patient data, that vaccine injuries are underreported to VAERS, and that less than 1% are actually reported.
The VAERS database, of which all of the reports were verified by the CDC (permanent VAERS number), and typically 86% of the reports are filed by doctors, coroners, and manufacturers. False reports are punishable for federal law.