Immunoprophylaxis of hepatitis B virus infection.
Hepatitis-B infection is a global health problem. The spectrum of the disease is highly variable ranging from mild disease to chronic liver diseases including hepatocellular carcinoma. There are approximately 350 million chronic Hepatitis-B surface antigen (HBsAg) carriers in the world. Till date there is no effective therapy against this disease. Hence, prevention of the disease through vaccination is the only means to control the disease. Passive immunization is recommended for certain accidental exposures. Hepatitis-B immunoglobulin (HBIG) contains high titers of anti-HBs prepared from pooled plasma. HBIG has been shown to be highly effective in preventing post exposure transmission. HBIG induces immunity for a short period only hence, it is recommended to have a course of active immunization following passive immunization. Active immunization is achieved using vaccination. Two generations of vaccines, 1st generation plasma derived and 2nd generation recombinant DNA vaccines are available. Both these vaccines have been used extensively in all age groups all over the world. The studies have shown that HB vaccines are clinically well tolerated, safe and highly immunogenic. Normally 3 doses of HB vaccines are recommended in 0, 1, 2 and 12 or 0, 1, 6 months schedule. The dosages and schedules may vary in certain special groups, such as infants and neonates, chronic renal failure patients on hemodialysis. Advisory committee on immunization practices (ACIP) has given several guidelines regarding HB vaccination. Universal immunization of all infants and integration of HB Vaccine in the expanded program of immunization has been recommended by World Health Organization. Universal infant immunization is cost effective. Universal immunization of infants is the only strategy that will lead to the control and eradication of HBV infection in all regions of the world. Several countries have adopted this policy. But in India we have several problems in implementation of this policy. The high cost of the presently available vaccine is one of the major factors. The future consideration for hepatitis vaccines are focussed on multivalent combination vaccines with other childhood vaccines, and use of immunomodulators in conjunction with vaccine to increase the efficacy of vaccines in immunocompromised hosts.
Department of Gastroenterology, Nizam's Institute of Medical Sciences, Punjagutta, Hyderabad - 500 082, India.
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