A while ago I ran into a report of an alleged side effect of the COVID-19 vaccine. It was a “this happened to my cousin” story, so it’s low on credibility. Some news outlets, though, claimed it couldn’t be true because there was no previous report of this effect.

That’s not a valid refutation. The vaccines are fairly new, and it’s plausible that a few people could have side effects that weren’t previously recorded. The media argument amounted to “We never heard of it before, so it couldn’t have happened.”
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