@Carl79 So do your calendar dates actually show as blocked, or are you registered to accept medical and other essential personnel, so the dates show as open?
If they show as blocked and you still got a Booking Request, contact Airbnb to find out why someone could send a request for blocked dates. If the calendar is open, for the purpose of hosting first responders, then you are still going to end up getting requests and inquiries from ordinary, clueless guests. If you haven't already, put at the top of your listing description that you are not open to normal bookings at this time, due to pandemic control. Then rather than decline inappropriate requests, try just messaging back, pointing out that you aren't hosting at the present time, and to please withdraw their request. If you can get them to withdraw it within the 24 hour time frame, you won't need to take a hit on acceptance rate.
If they are Inquiries, rather than booking requests, you don't need to either pre-approve or decline- just messaging back fulfills your responsibilities and doesn't impact your stats.