Chapter 116. Immunization Principles and Vaccine Use (Part 2)

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Approaches to Passive Immunization Passive immunization is generally used to provide temporary immunity in a person exposed to an infectious disease who has not been actively immunized; this situation can arise when active immunization is unavailable (e.g., for respiratory syncytial virus) or when active immunization simply has not been implemented before exposure (e.g., for rabies). Passive immunization is used in the treatment of certain illnesses associated with toxins (e.g., diphtheria) as well as for some snake and spider bites and as a specific or nonspecific immunosuppressant [Rho(D) immune globulin and antilymphocyte globulin, respectively]. ...

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Chapter 116. Immunization Principles and Vaccine Use (Part 2) Approaches to Passive Immunization Passive immunization is generally used to provide temporary immunity in a person exposed to an infectious disease who has not been actively immunized; this situation can arise when active immunization is unavailable (e.g., for respiratory syncytial virus) or when active immunization simply has not been implemented before exposure (e.g., for rabies). Passive immunization is used in the treatment of certain illnesses associated with toxins (e.g., diphtheria) as well as for some snake and spider bites and as a specific or nonspecific immunosuppressant [Rho(D) immune globulin and antilymphocyte globulin, respectively]. Three types of preparations can be used in passive immunization: (1) standard human immune serum globulin for IM or IV administration; (2) special immune serum globulins
with a known content of antibody to specific agents (e.g., hepatitis B virus or varicella-zoster immune globulin); and (3) specific animal antisera and antitoxins. Postexposure Immunization For certain infections, active or passive immunization soon after exposure can prevent or attenuate disease expression. Recommended postexposure immunization regimens are shown in Table 116-1. For example, giving either measles immune globulin within 6 days of exposure or measles vaccine within the first few days after exposure may prevent symptomatic infection. Nonimmune pregnant women exposed to rubella can minimize clinical illness by postexposure passive immunization; however, this measure may fail to prevent viremia and infection of the fetus and thus may be followed by the congenital rubella syndrome. Proper immunization for tetanus plays an important role in dirty-wound management. The need for active immunization—with or without passive immunization—depends on the wound's condition and the patient's immunization history. Tetanus is rare among persons with documented receipt of a primary series of tetanus toxoid doses. Tetanus immune globulin is helpful in patients with clinical tetanus, but survivors must be actively immunized since the disease does not stimulate protective levels of antitoxin antibody. Administration of rabies immune globulin plus rabies vaccine in the immediate postexposure period is highly effective in preventing disease. Similarly, for persons who have not been actively immunized, administration of hepatitis A immune globulin within 2
weeks of exposure to hepatitis A virus is likely to prevent clinical illness. Evidence also supports the efficacy of human hepatitis B immune globulin in preventing disease after exposure. While no high-titer preparation is available for postexposure protection against non-A, non-B hepatitis, standard human immune serum globulin is efficacious. VariZIG, a highly purified preparation of human antibody to varicella-zoster virus (VZV), is licensed in Canada for the prevention of varicella in nonimmune pregnant women who are exposed to infected individuals. At the time of this writing, this product is available in the United States from the Centers for Disease Control and Prevention (CDC) under an investigational new drug (IND) protocol or under an expanded-access program through the U.S. Food and Drug Administration. Table 116-1 Recommended Postexposure Immunization with Immunoglobulin Preparations in the United States Disease Indicated Comments Measles Yes Standard human immune globulin is recommended for exposed infants and adults with normal immunocompetence (but with a contraindication to measles vaccine) and for
immunocompromised patients exposed to measles (regardless of immunization status). Patients should be actively immunized 3–6 months after immunoglobulin administration. Recommended dose: 0.25–0.50 mL/kg (40–80 mg of IgG/kg) IM; 80 mg of IgG/kg for immunocompromised contact; maximum, 15 mL. Rubella No Efficacy is unreliable; therefore, standard human immune globulin is recommended for administration only to antibody-negative pregnant women in the first trimester who have a documented rubella exposure and will not consider terminating the pregnancy. Recommended dose is 0.55 mL/kg (90 mg of IgG/kg) IM. Tetanus Yes Human tetanus immune globulin (TIG) has replaced equine tetanus antitoxin because of the risk of serum sickness with equine serum.
Recommended dose for postexposure prophylaxis is 250–500 units of TIG (10–20 mg of IgG/kg) IM. Recommended dose for treatment of tetanus is 3000–6000 units of TIG IM. Rabies Yes Human rabies immune globulin (RIG) is preferred over equine rabies antiserum because of the risk of serum sickness with equine serum. RIG or antiserum is recommended for nonimmunized individuals with animal bites in whom rabies cannot be ruled out and with other exposures to known rabid animals. Recommended dose of RIG is 20 IU/kg (22 mg of IgG/kg). Recommended dose of antiserum is 40 IU/kg. Rabies vaccine is given as well at 0, 3, 7, 14, and 28 days. Hepatitis Yes Standard immune serum globulin is A given in a single dose of 0.02–0.04 mL/kg or (for continuous exposure) in a dose up to 0.06
mL/kg every 5 months. Postexposure treatment with hepatitis A immune globulin has not been studied. Varicella Yes VariZIG, a new Canadian purified human immune globulin containing high-titer IgG antibody to varicella-zoster virus, is intended for patients without evidence of immunity to varicella who are exposed to infection and who are at high risk for severe disease and complications. It is not currently licensed in the United States but instead has investigational new drug status. VariZIG may be obtained under expanded-access provisions for patients who meet the enrollment criteria and choose to participate. Maximal benefit requires administration within 96 h of exposure. The recommended dose is 125 units/10 kg of body weight, up to a maximum of 625 units.