INTRODUCTION

Without question, immunization against many infectious diseases has dramatically reduced mortality and morbidity, especially among children in both industrialized and developing areas of the world. The impact grew over the last half of the 20th century, with major reductions in disease burden caused by polio, measles, rubella (with respect to congenital defects), and varicella viruses and by invasive bacteria such as Haemophilus influenza, various pneumococci, and Bordetella pertussis, among others. The long-term effect on serious disorders such as liver cancer, caused by the hepatitis B virus, or cervical cancer, caused by the human papilloma virus (HPV), remains to be seen. Despite this clear medical success, vaccines have become the focus of considerable social and ethical controversy.

MORAL JUSTIFICATION FOR IMMUNIZATION

Immunization has two principal purposes: (1) the prevention of harm to individuals who receive vaccines and therefore develop protective immunity and (2) a reduction in social burdens associated with infection. The latter occurs both because of the economic savings associated with the direct cost of care, as well as such things as lost time and income on the part of caregivers, and because of the phenomenon of herd immunity, which reduces the spread of disease throughout a population, even to those not vaccinated or to those whose immunity has waned or become impaired as a result of unrelated diseases or treatment (e.g., HIV infection, cancer chemotherapy, and the use of steroids for rheumatological disorders). Thus, we justify vaccination primarily on the basis of its direct beneficial effect: the development of immune protection against disease, in individuals and in populations.