Yes, it’s a worry and yes, people are suffering a diverse and serious range of symptoms but… this behaviour by the virus – mutating and/or coming back within the same host is by no means novel.
Many types of flu recur and the symptoms are not always the same, nor of the same intensity. This is a long-standing and well-known feature of such virus.
The fact that the virus has multiple variants (a fact that has been confirmed, denied, then confirmed again) and that it appears to mutate means that virologists are constantly chasing it to understand it – and until they understand it, no one can produce a vaccine that will work in, even, most cases.
Even more complicated is the question as to whether the virus attacks different races in different ways or if there is more than one form of the virus and infection, or severity, depends on race.
Given that it is now established that the strain most prevalent in Italy is different to that most prevalent in the UK and from that most prevalent in Pakistan and from that most prevalent in Malaysia and so on, it is clear that while there are core elements to them, they are not the same and therefore treatment and possible immunisation must take account of that.
Racial markers, locality, age and just sheer bad luck seem to have at least some responsibility.
There are a number of different vaccines being developed.
The Russian vaccine touted by President Putin appears to have been, either, a hoax or a wildly optimistic statement.
If all of the others are all working on identical strains of the virus, then we are gaining the chance for a quick response but losing the chance to develop what we might term a broad-spectrum vaccination.
Ditto with treatments.