We live in a free and liberal world - mostly - and so it would seem on the face of it that anything is fair game for a laugh. Religion, politics and relationships are the regular butts of jokes, and by and large they all work. However, there are exceptions. Choose the wrong religion to have some fun with and you could find yourself at the wrong end of a Fatwa and in hiding for the rest of your adult life. Obviously this seemed to work well for Salman Rushdie as he somehow came out of hiding married to a supermodel whilst looking even more like an extra from Harry Potter. Politics is OK as long as you don't aim it at a dissident group who set their own agenda and come fully armed and ready to pop an IED through your letterbox.
Illness is really tricky ground, and unless you're a testicular cancer survivor, and now have pickled onions where your privates used to be, it's pretty hard to get away with. Covid-19 could be different though, mainly because nobody has the slightest idea of what is going on.
What was described as a killer disease and deadly virus, now accounts for less deaths than skipping, and yet people are ploughing their way around supermarkets in slow motion moonwalks complete with sanding masks from Wickes. In the Midlands, the knock effect of old ladies spending several minutes deciding which fish fingers, has caused queues over half a mile...our main government advisor rated the advice he rolled out for the rest of the country so optional that he popped up to the other end of the country to see his parents whenever his kids needed looking after...and Donald Trump was offering to inject the entire American public with disinfectant.
So, there is humour in there, and plenty of it. All you need to work out is if anyone associated with the wedding has carced it, but the thing is, every wedding has sad news attached to it. Short of sending out a survey asking everyone, the really is very little you can do in terms of research. Maybe keep the humour general and don't allude to any specific like melting lungs...or maybe don't go there at all.