Protection from Infection or Protection from Disease?
The memory response elicited by most human viral vaccines does not protect against reinfection, but rather against the development of disease. An individual may be exposed repeatedly to viruses and never be aware of it, because the memory response eliminates the virus before signs and symptoms develop. After vaccination with inactivated poliovirus vaccine, virus replication may take place in the intestine, but effectively blocks the development of poliomyelitis. On the other hand, the human papillomavirus vaccine is over 90% effective at blocking infection. Consequently the HPV vaccine induces sterilizing immunity.
