Put up No Trespassing signs. Then they are breaking the law if they come and knock.
NO TRESPASSING signs are the way to go, but property owners need to specify what trespassers are illegal. “Anyone entering on this private property to inquire in any manner about any medical matter protected by HIPPA or relating in any manner to the personal medical vaccination status of occupants is deemed to be illegally trespassing and will be prosecuted to the full extent of the law.”