I don't think the study is as easy to replicate as you think. It requires correlating test results and vaccination records. Although both of those data sets probably exist, they are sensitive, probably held by different parties. Joining them should be difficult.

As to the study, I'm not really clear if you're objecting to the research itself or to it being posted on HN, but both those positions seem unreasonable. I agree that publicity value sometimes derives from novelty, and that might, in the end be traced to an unfortunate coincidence in the data. But replication and/or review should address that. And if it is as easy as you hint, that should happen quickly and at low cost.