At least one other COVID-19 proposal has been closed, and I'm not sure how this one is different.
I did not make either proposal, but this one certainly looks very different. The title is perhaps more appropriate since it's just "covid19" instead of the very long title of the previous proposal. Also the example question is very different from the ones in the previous proposal, and in my opinion it is a very good example question and appropriate for stack exchange.
I do think that since COVID-19 only refers to one disease (the disease caused by SARS-CoV-2), the scope is a bit narrow and perhaps ephemeral. Hopefully discussion about COVID-19 will not be so commonplace 10 years from now, so perhaps a proposal with title "Pandemics" or "Epidemiology" or "Virology" would be more appropriate, though "virology" probably falls under Biology.