Yes, but only seniors get that, because your immunity to chicken pox, if you get it as a child, lasts most of your lifetime. It’s not until you are older and your immune system starts weakening that you are at any risk for reinfection.
Very true, but this author seems to have picked a bad example for a disease where lasting immunity is permanent.
For Covid it is also seniors who are most at risk, and may not have long lasting immunity from either infection of the vaccine and thus require regular boosters.