The difference is that anti-vaxers make this point against vaccines that have been used for a long time about which we do understand the long term health consequences.

This is contrasted to the long term health consequences of COVID-19, which appears could be significant, but we just aren't certain yet only because there just aren't any long term survivors yet and thus studies [0] related to it haven't been completed. I don't think this is past the limit.

0 - https://www.nhlbi.nih.gov/news/2020/looking-forward-understa...