Chapter 116. Immunization Principles and Vaccine Use (Part 8) Current recommendations also include influenza vaccine for routine annual administration to individuals with chronic illness at any age, to persons living in the same household as chronically ill individuals, and to all adults >50 years of age. Polyvalent pneumococcal polysaccharide vaccine is similarly recommended for adults ≥65 years of age and for all chronically ill persons. Hepatitis B vaccine should be given to adults at high risk from clinical, occupational, behavioral, or travel exposures, including patients undergoing hemodialysis, routine recipients of clotting factors, health care workers exposed to potentially infected blood or blood products, individuals living and working in institutions for the mentally handicapped, travelers to highly endemic countries, persons at excess risk for sexually transmitted diseases, injection drug users, and household contacts of known carriers of hepatitis B surface antigen. Hepatitis A vaccine is recommended for these same groups and for persons with clotting disorders or chronic liver disease. There are a number of other special-use vaccines whose administration is related to travel and occupational exposures (e.g., Japanese B encephalitis, typhoid fever, yellow fever, and rabies); specific recommendations for the use of these vaccines in the United States can be found at www.cdc.gov/nip/recs/adult- schedule.htm. Simultaneous Administration of Multiple Vaccines There are no contraindications to the simultaneous administration of multiple individual vaccines, although the use of licensed combination vaccines can significantly reduce the required number of injections during the first 2 years of life. Combination DTaP/Hib vaccine should not be used for primary immunization of infants because it results in a blunted, suboptimal response to Hib; the combination may be used for booster immunizations. Simultaneous administration of the most widely used live and inactivated vaccines has not resulted in impaired antibody responses or in elevated rates of adverse reactions. In fact, this approach increases the likelihood that a child will ultimately be fully immunized. The simultaneous administration of vaccines is useful in any age group when the potential exists for exposure to multiple infectious diseases during travel to endemic countries. Live-virus vaccines may be given together on the same day; if this approach is not feasible, an interval of at least 30 days should be allowed to avoid interference in the response to one or another of the administered vaccine strains. Because high doses of immune globulin can inhibit the efficacy of measles and rubella vaccines, an interval of at least 3 months is recommended between the administration of immune globulin and that of MMR vaccine or its components. However, postpartum vaccination of rubella-susceptible women should not be delayed because of the administration of anti-Rho(D) immune globulin or any other blood product during the last trimester or at delivery. Should the administration of an immune globulin preparation become necessary after vaccination, it should be postponed, if at all possible, for at least 14 days to allow time for vaccine-virus replication and development of immunity. In general, there is little interaction of immune globulin with inactivated vaccines, and postexposure passive prophylaxis can be given together with hepatitis B vaccine or tetanus toxoid, resulting in both immediate and long-lasting protection. Adverse Events Vaccines are generally very safe. Serious adverse events proven to be due to currently licensed vaccines are rare. Concerns about vaccine safety have at times become inflated in conjunction with complacency about the consequences of infections no longer routinely transmitted in the United States. As a result, some parents have refused to have their infants and children immunized. An adverse reaction or vaccine side effect is an untoward vaccine effect that is extraneous to the vaccine's primary purpose (to produce immunity). An adverse event can be either a true vaccine reaction or an event whose occurrence is temporally related to a vaccine dose but is entirely unrelated to the vaccine itself. As vaccines are routinely administered through childhood, coincidental events are inevitable. Because our understanding of the underlying biologic mechanisms that cause adverse events remains limited, a few highly publicized claims— unsubstantiated by validated data or analysis—can easily heighten the suspicion that some or all vaccines routinely cause unacceptable adverse events. Antivaccine advocacy groups actively encourage the avoidance of immunization because they believe that vaccines cause certain disorders (e.g., autism). This situation presents a challenge to physicians and public health officials who must educate parents and practitioners about vaccine benefits and risks. It is true that modern vaccines, while remarkably safe and effective, are associated with adverse events in some recipients and that these events range from frequent and mild to rare and serious or even life-threatening. The decision to recommend a vaccine involves an assessment of the risks of disease and its complications for those who remain unimmunized and the benefit-to-risk ratio of vaccination itself. Because these factors may change over time, the balance between societal benefits and individual risks must be continually evaluated. Valid and invalid contraindications to childhood immunization and appropriate precautions in the use of specific vaccines are reported by the CDC (Table 116-3); updated information can be found at www.cdc.gov/vaccines/recs/vac- admin/downloads/contraindications_guide.pdf. A putative link between measles immunization and autism has been the subject of intense international controversy. The Institute of Medicine of the U.S. National Academies of Science has issued four recent reports whose findings (1) fail to support hypotheses that vaccines are associated with multiple sclerosis, neurodevelopmental disorders (e.g., autism), or immune dysfunction; (2) provide no evidence for a temporal association of these conditions with vaccination; and (3) elucidate no biologically plausible basis for the purported relationships. . Chapter 116. Immunization Principles and Vaccine Use (Part 8) Current recommendations also include influenza vaccine for routine annual administration. some or all vaccines routinely cause unacceptable adverse events. Antivaccine advocacy groups actively encourage the avoidance of immunization because they believe that vaccines cause certain. Combination DTaP/Hib vaccine should not be used for primary immunization of infants because it results in a blunted, suboptimal response to Hib; the combination may be used for booster immunizations.