The initial motives behind development of vaccines were to protect against life-threatening infections (eg, rabies, diphtheria), to eradicate sweeping outbreaks of serious diseases (eg, paralytic poliomyelitis, smallpox), and to prevent diseases in a vulnerable population by the immunization of surrogates (eg, rubella immunization to prevent congenital rubella syndrome). Now a fourth motive emerges: prevention of less serious infections to improve quality of life. The advantages of new vaccines and immunization programs should no longer be measured exclusively in terms of the number of lives saved but should take into account direct and indirect cost savings and overall benefit to individual and societal health and well- being. Although varicella and hepatitis A infections can be life threatening, most cases are self-limited and have no significant sequelae. Immunization is more likely to improve quality of life than to save lives. Vaccination against typhoid remains a potentially lifesaving act in developing nations, but even the newer typhoid vaccines were developed primarily to reduce the frequency and severity of adverse reactions to immunization rather than to improve the protective efficacy of the original heat-phenol inactivated vaccine. Varicella virus vaccine, hepatitis A virus vaccines, and the typhoid polysaccharide Vi capsular vaccine represent important additions to immunization agents. These vaccines are immunogenic, clinically effective, and generally safe, with infrequent and usually mild adverse reactions. Their favorable benefit-risk ratio should encourage their appropriate use. The Centers for Disease Control and Prevention, the American Academy of Pediatrics, and the American Academy of Family Physicians have already recommended varicella vaccine for universal immunization of children. Formal recommendations that hepatitis A vaccine also be routinely used for all children may be forthcoming in the next few years; in the meantime, persons at high risk should be immunized. Typhoid vaccination will likely continue to be used selectively for those who have significant contact with the organism or those who travel to typhoid-endemic countries.
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