Comparing benefits and risks of immunization

Background: This paper uses a straightforward method of quantifying the ben efits and risks of immunization, illustrated by universal immunization prog rams in British Columbia against invasive Haemophilus influenzae type b dis ease (Hib), measles, rubella, and paralytic poliomyelitis. Methods: Data were extracted from provincial communicable disease and vacci ne adverse event surveillance systems. Average disease incidence was compar ed before and after implementing universal immunization programs. Estimates of prevented deaths and serious disease complications were calculated and compared with expected numbers of serious vaccine-associated adverse events (VAAEs). Results: Average incidence of reported cases decreased 90 to 100% over a 5- year period after implementing universal programs. These benefits were sust ained or strengthened over time. Rates of reported serious VAAEs were low. Discussion: The remarkable success of immunization has created a paradox. D espite a low absolute risk of serious VAAFs, the relative risk of some VAAE s can exceed risk of disease in the province.