Our knowledge of Covid-19 changes every day. Hindsight is misleading when it comes to science | Gideon Meyerowitz-Katz

It's tempting to look back and say if only we had known' - but that ignores the realities

The results of a Covid-19 study have been announced. Unlike most of the previous results, this study seems immediately to be a game-changer - rather than minor benefits from an expensive drug, or spurious nonsense from a dubious trial, these results show that a cheap and common medication, dexamethasone, could reduce the risk of death in people with severe disease by a substantial amount. The study was large enough to be meaningful and its finding likely to be true.

This is, without qualification, fantastic news.