There has been a huge influx of people trying to upload scammy covid apps. As a result the mere mention of covid is enough to get your app flagged automatically.
I don't currently work on a covid app, but I know somebody who does. Their app was flagged but they were able to resolve it by contacting google.
Do they happen to be government-funded, or represent a health company as stated above? To be fair, I didn't follow up the rejection, I just assumed the rule would be set in stone and they wouldn't budge. The app was free, no ads or any method to profit from covid so I was pretty shocked.
I don't remember the specifics since I thankfully don't get my apps rejected often, but there should be a button to contact the play store support somewhere in the play store UI.
Unfortunately in this kind of situation, the play store handling, while understandable, does not make it easy for legitimate covid apps to be posted.