Academic journal article Canadian Journal of Public Health

Comparing Benefits and Risks of Immunization

Academic journal article Canadian Journal of Public Health

Comparing Benefits and Risks of Immunization

Article excerpt

ABSTRACT

Background. This paper uses a straightforward method of quantifying the benefits and risks of immunization, illustrated by universal immunization programs in British Columbia against invasive Haemophilus influenzae type b disease (Hib), measles, rubella, and paralytic poliomyelitis.

Methods: Data were extracted from provincial communicable disease and vaccine adverse event surveillance systems. Average disease incidence was compared 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 sustained or strengthened over time. Rates of reported serious VAAEs were low.

Discussion: The remarkable success of immunization has created a paradox. Despite a low absolute risk of serious VAAEs, the relative risk of some VAAEs can exceed risk of disease in the province.

ABREGE

Contexte: L'etude emploie une methode simple pour quantifier les avantages et les risques de (immunisation, tell qu'illustres par les programmes de vaccination systematiques de la Colombie-Britannique contre (infection invasive at HiB (hemophilus influenzae B), la rougeole, la rubeole et la poliomyelite paralytique.

Methode: Nous avons extrait des donnees des systemes provinciaux de surveillance des maladies transmissibles et des reactions adverses aux vaccins, puffs compare (incidence moyenne des maladies avant et apres la raise en oeuvre de programmes de vaccination systematiques. Nous avons ensuite estime les deces et les complications graves &wites, que nous avons compares avec le nombre attendu de reactions adverses vaccinales (RAV) graves.

Resultats : L'incidence moyenne de cas declares a diminue dans une proportion de 90 h 100 % sur cinq ans apres la mise en oeuvre des programmes systematiques. Ces avantages se sont maintenus ou renforces avec le temps. Les taux declares de RAV graves etaient faibles.

Question a dbattre : Le succes remarquable de la vaccination entraine un paradoxe: bien que le risque absolu de RAV grave soit faible, le risque relatif de certaines RAV peut &passer le risque de la maladie dans la province.

Success of immunization programs depends on sustained public acceptance that individual and collective benefits of immunization outweigh the risks. The benefits and safety of immunization are questioned by some persons or groups who are generally opposed to immunization.1-5 Parents must evaluate conflicting claims and counter-claims about immunization.6 Health professionals' role in informing parents about the benefits and risks of immunization is increasingly challenging.6,7

Misunderstanding of the benefits and safety of immunization is fueled by two converging trends, leading some parents to believe that the risk of immunization exceeds the risk of disease. First, the incidence in Canada of many vaccinepreventable diseases has decreased to such low levels that some parents question the need to immunize their children.2,8,9 This attitude may be reinforced by a minority of parents whose children have not been immunized, yet who have indirectly benefited from disease protection afforded by high levels of vaccination-derived population immunity10,11 - a phenomenon known as "herd immunity". 12 Some persons also believe that the decline in vaccinepreventable diseases is more related to other factors, such as improved public sanitation, better nutrition or accessible, highquality health care.5,13

Second, there is increased awareness of vaccine-associated adverse events (VAAEs) or instances when immunization has failed to prevent disease.14 Since vaccines are neither 100% effective, nor 100% safe,5,9,15 incidents of break-through disease in immunized persons and reports of VAAEs are expected and reasons for continued disease surveillance and monitoring of VAAEs. …

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