I have severe allergies where I moved to Texas became allergic asthma. I invested in proper air purifier's and man the difference is amazing.
Some other things folks should look at:
Level of Micron of contaminants trapped
Does it have a pre-filter with the filter
I run honeywell kit and have to exchange the pre-filters out every 2-3 weeks and every year have to swap out the hepa filter.
We live in a high pollen, high seed, and farm area (with horses and cats) and you would be shocked at how much is collected.
How good is it? I can track on my blood pressure based upon dirtiness of the filters ...
COVID is like pollen ... so the analogy is similar