Yes. If there's a nuclear explosion close enough that you need to take shelter, 911 isn't coming whether you tell them you have COVID or not, assuming you can even reach them, which is dubious.

> If there's a nuclear explosion close enough that you need to take shelter, 911 isn't coming

Not necessarily true. Even if you are quite far away, going inside to avoid the fallout is a very strategy and 911 will (most likely) at least be available.