Myocarditis Cases Reported After mRNA-Based COVID-19 Vaccination in the US From December 2020 to August 2021

Here’s the key paragraph:

Furthermore, as a passive system, VAERS data are subject to reporting biases in that both underreporting and overreporting are possible.38 Given the high verification rate of reports of myocarditis to VAERS after mRNA-based COVID-19 vaccination, underreporting is more likely. Therefore, the actual rates of myocarditis per million doses of vaccine are likely higher than estimated.

I agree. Underreporting is more likely. In fact, the term “overreporting” wasn’t even mentioned in the reference they cite. I can’t even figure out how VAERS could be overreported since the system should eliminate duplicates unless there is a bug.

But the key thing here is they did absolutely nothing to attempt to quantify the underreporting factor (URF).

They absolutely know how to estimate it. John wrote the paper on how to do that in November 2020: The reporting sensitivity of the Vaccine Adverse Event Reporting System (VAERS) for anaphylaxis and for Guillain-Barré syndrome.