Earlier quoted context omitted.
The intervention is Metformin during Covid onset?
I had the same question. Apparently people who had already been taking Metformin for diabetes were at lower risk of severe Covid [1], which explains why Metformin is being studied. Looks like the same authors found that Metformin as a treatment after Covid diagnosis did not significantly reduce the the risk of hospitalization or death, even though it does reduce incidence of long Covid. [1] https://www.covid19treatme…
https://clinicaltrials.gov/study/NCT04510194?term=NCT0451019...
Spoiler: "None of the three medications that were evaluated prevented the occurrence of hypoxemia, an emergency department visit, hospitalization, or death associated with Covid-19." [https://pubmed.ncbi.nlm.nih.gov/36070710/]
But they already had this population enrolled when Long Covid started becoming an issue, so they extended the study to see what impact the same 3 drugs would have on incidence of long covid.