a few thoughts.
silver what ever is effective against infectious buggers because it carries an electric charge that kills the little buggers on contact. the same reason silver is used to make anti stink cloth. Copper works as well(so does gold platinum ect.) Its also why zinc lozenges shorten colds.
Note do not take zinc willy nilly. while its unlikely to kill you it can destroy your sense of smell and taste permanently. If you are going to be forced to be in a germ incubator it may(stress may) be wise to take a lozenge after exposure. Covid-19) seems to anchor in the back of the throat, fester and then move down to the lungs.
For your compromised elders, the best thing you can do is make sure mold is not an issue in their environment and then increase the humidity they live in to (guess) 20-40%. If you can buy them an electrostatic generator, making particulates cling to the walls.
I used to have terrible troubles with sinus infections. Had the roto-rooter surgery to open things up, which helped some, but not enough.
Started using a neti pot, which helped some, but not enough. Sinus infection turned to pneumonia Dec of ‘17.
Bought a Navage and started using it fall of ‘18. Sinus infection turned to pneumonia in Dec of ‘18.
Last fall I started adding an ounce of Silver Biotics brand colloidal silver solution to the Navage rinse. Haven’t had so much as the sniffles since.
Coincidence? Maybe, but I like to think not.