Lung infections come from improperly cleaned or maintained CPAP machine and failure to change out the water in the humidifier.
I clean and maintain mine regularly (change the water, use distilled water, clean everything, etc) and have not had a single lung infection. Starting Vitamin D four years ago helped a lot, too.
Presuming the supplementing you’ve been doing has ensured you will have good bioavailable Vitamin D flowing through your veins if and when your immune system needs it, how’d you fare during the recent COVID-19 unpleasantness?
Did you avoid the worst symptoms even if infected with COVID-19?