VAERS reports what VAERS gets, but of all the people I know that got vaccinate, we are the only ones that put it on our Iphones when first vaccinated. It was on the paperwork as an invitation, so we did. The article, (I think) capture maybe 1%, 1 out of a hundred, as most people throw the papers away as soon as the get home or just don't want to fool with it.
Once in, you answer initial questions, the for a few weeks you get a text, that links you to about 3 questions and the basically says have a nice day. Then it changes to once a month, I guess just to make sure you aren't dead. About the time we got the first booster that fall, it added the question of have we got the booster, when I replied yes, it started the daily thing and wound down again.
I've spent some time querying the VAERS database online at the website. It's a little tricky but amazing what you can find out, total, stats, group by vaccine manufacturer, date range, seriousness of effects or deaths, page after page of individual reports, and not just about the Covid vaccine but other vaccines as well. If you are a wonk, it is all downloadable for spreadsheet analysis once you set it up correctly. I didn't, as I got my fill of spreadsheet analytics in the military and in business, so now I let other do the analytics.