Look up germ theory vs terrain theory. I think the most important part of it is that your outlook on disease will start out as seeing a deadly world out there trying to kill you in germ theory and you need special protection from medicines. As you understand terrain theory the Outlook becomes that if your body is weak it invites disease and so the power of fighting diseases is completely in your own hands. Just to add some practical info, rubella is a virus and similar protocols for covid such as zinc, quercetin, vitamin c, vitamin d should suffice to prevent any issues