Pondering this, Jenner concluded that cowpox not only protected against smallpox but also could be transmitted from one person to another as a deliberate mechanism of protection. —"Edward Jenner and the History of Smallpox and Vaccination," Stefan Riedel Which piece of evidence in this passage supports the text’s central claim? Jenner had the idea of spreading cowpox intentionally. Jenner figured out that cowpox can be prevented. Jenner decided that people should have smallpox before they have cowpox. Jenner thought that cowpox could not be transmitted.