It's the mutating spike proteins being shed from the "vaccinated" who are essentially walking bioweapons whose bodies engineer it, indefinitely. The bodies keep replicating the spike proteins and shed it onto other people.
True vaccines have nucleocapids that, supposedly, trigger the immune system to build upon itself and target intended viruses. The Covid "vaccine" is (intentionally) completely devoid of nucleocapids but instead have spike proteins which systemically destroy the body's cells, thereby, effecting an extremely wide range of pathogenicity (from artery damage in legs to prion colonization in the brain).