It is not merely that people are old that makes them susceptible to Covid-19. It is other factors that correlate with age that make them more susceptible. One of those factors could very well be lack of vitamin d.

I'm guessing wrinkles and gray hair make covid worse, too. Hair dye and facelifts for everyone!

Sick people lack vitamin D. Most people grow sick when they get old. Sickness and autoimmune diseases exposes to Covid-19.