Neither me or family members who got seasonal allergies / flu before we started taking D3 never had smell or taste completely disappear.
Relatives who got CD19 said that they knew that they got virus when taste and smell disappeared.
I got H1N1 in 2009 and lost all taste and smell but only for a couple of days.
A friend of mine got C19 last fall. While it was a pretty mild case, thank goodness, she lost taste and smell for about a month and then things tasted different and “off” to her for a couple more months.