Most of what we know about coronavirus will change [es]
According to this article, most of what has been published about coronavirus hasn't been peer reviewed.
https://m.eldiario.es/sociedad/Paciencia-leas-coronavirus-va-cambiar_0_1008249584.html
The value of peer review depends a lot on the journal. There are predatory journals that publish any crap if you pay the fee. And there are serious journals. (And there are some journals in between.)
Anyway, the peer review is not a proof that the paper is correct or that the data is real. It's only a check that the article is minimally inteligible and the result makes a minimal sense. People has published fake data. Some articles are just wrong. (Publishing usually involves a few review suggested by the referees and editors. It is not so easy. But a lot of articles slip through the cracks.)
In a good journal the peer review filter the very bad articles and the bad articles, but there are some articles of dubious quality that has been published. (Some get famous, like the arsenic in bacterias, of cold fusion.)
Most bad preprints and bad articles are just ignored. This part of science is protected by obscurity. The problem is that in this emergencies, any preprint or press release is immediately repeated in all major media, forums, facebook, and whatever other platform is out there. So the bad articles have a lot of diffusion.
> La importancia del cribado periodístico
Just assume there is no filtering by the journalism. Many just start the article with "According to a recent scientific study" and then they repeat whatever the article says.
Honestly it's no different to normal.
You have to look at who is making the claim and if they can back it up.
And if it's outlandish they really really need to back it up.
Maybe there needs to be more of a barrier of entry or a fee paid or a rating system with punishments.
But that's the same problem as peer review.