1. The Historical Medical Library of The College of Physicians of Philadelphia. Crookshank, E.; ed. History and Pathology of Vaccination, vol. 1. London: Lewis, H. K. 1889.
2. American Academy of Pediatrics, “Vaccine Safety: The Facts,” www.aap.org, 2008.
3. (a) www.who.int/immunology WHO (2019); (ii) Vanderslott, S.; Roser, M. https://ourworldindata.org/vaccination Vaccination.
4. CDC, “Smallpox Disease Overview,” www.cdc.gov, 2004.
5. (a) Varki, A. Glycobiology, 1993, 3, 97-130