Hepatitis B virus (HBV) is the cause of significant disease worldwide. Acute infectionoccurs with hepatitis B, but chronic asymptomatic infection leading to chronic liverdisease and hepatocellular carcinoma (HCC) is a lifelong concern. Infections ininfants and pre-school age children are at greatest risk of becoming chronic, therebyincreasing the risk of cirrhosis and primary HCC later in life, which is probablydue to the effect of age on the immune system's ability to clear and eliminate the infection. Treatmentfor hepatitis B is rarely effective with current medications.

Global burden of Hepatitis B: Globally, hepatitis B is one of the most common infectious diseases. Estimatesindicate that at least 2 billion people have been infected with HBV, with over 378million people being chronic carriers (6% of the world population). Some 4.5 millionnew HBV infections occur worldwide each year, and 15-40% of those infectedwill develop cirrhosis, liver failure, or hepatocellular carcinoma.

On the basis of sero-epidemiological surveys, the World Health Organization(WHO) has classified countries into three levels of endemicity according to theprevalence of chronic HBsAg carriage: high (8% or greater), intermediate (2-8%),and low (less than 2%). In India, HbsAg prevalence of carriers is 4.2%, which is second highest in the world after China which means that there are estimated 40 million carriers in India. It is estimated that 30 - 40% of the total population show some serological markers of past infection with HBV.In endemic areas, HBV infection takes place in infancy and early childhoodwith perinatal transmission accounting for most chronic HBV infection.

Transmission of Hepatitis B: The primary routes of transmission are perinatal, early childhood exposure (often called horizontal transmission), sexual contact, and percutaneous exposure to blood or infectious body fluids (i.e.,injections, needle stick, blood transfusion).The likelihood of an infant developing chronic HBV infection is70-90% for those born to HBeAg-positive mothers and less than 15% for those born to HBeAg-negative mothers.

Prevention of Hepatitis B: The best approach to HBV control is prevention by vaccination and by screeningof blood products and organ donors. Recombinant HBV vaccine is effectivein 97% of at risk infants.

Hepatitis B vaccine: Hepatitis B vaccine consists of purified HBsAg particles producedthrough recombinant DNA technology in yeast.More recently, so-called third-generation hepatitis B vaccines - based on theS-, preS1-, and preS2-antigens, or using new adjuvants - have been and are beingdeveloped. These vaccines specifically aim to enhance the immune response inimmunocompromised persons and nonresponders.

Immunization schedule: Immunization against hepatitis B requires the intramuscular administration ofthree doses of vaccine given at 0, 1, and 6 months. More rapid protection (i.e.,for health care workers exposed to HBV or the susceptible sexual partner of apatient with acute hepatitis B) can be achieved through the adoption of an acceleratedschedule using three doses of vaccine administered at 0, 1, and 2 monthsfollowed by a booster dose given at 12 months. Various Hepatitis B schedules recommended by Indian Academy of Pediatrics are:
(i) Birth, 1 and 6 months
(ii) Birth, 6 and 14 weeks
(iii) 6, 10 and 14 weeks
(iv) Birth, 6 weeks, 6 months
(v) Birth, 6 weeks,10 weeks, 14 weeks

Dosing: For a child <10 years, 10 mcg/dose is advocated and for a child> 10 years, 20 mcg. It is given IM in the anterolateral aspect of thigh, or in the deltoid muscle in older children. Avoid using gluteal region, as the fat mass is large in that area which can lead to poor sero response.

Seroprotection: Seroprotection against HBV infection is defined as having an anti-HBs level >10 IU/L after complete immunization. Response to a three-dose series is excellent in all age groups,producing antihepatitis B antibodies (anti-HBs) in 85% to 99% ofrecipients. People with immunodeficiencies, renal failure,have poorer response, and higher dosages are recommended.Passive immunisation at birth with HBV immunoglobulinis also required if the mother is HBeAg positive and vaccine is given in allcases at birth with 2 or 3 subsequent vaccinations over 6 months so that all exposedchildren should receive at least three doses.

Booster dose: Boosterdoses of hepatitis B vaccine are not recommended for any age group;however, the need for booster continues to be evaluated.

Delay in between doses: Hepatitis B induces strong T cell response and memory. Anamestic response occurs even when the antiHBs titre had become undetectable.Hence according to the latest data there is no need to revaccinate the child even if the gap between the first and the second dose is more than 6 months, and that between 2nd and 3rd dose is more than 1 year. Instead just complete the three doses of vaccination as the child remains unprotected till the course of 3 doses are completed.

Hepatitis B vaccine in preterm babies: Studies show that response to hepatitis B vaccine may be diminished in infants with birth weight less than 2000 grams after administration of hepatitis B vaccine at birth. However, by 1 month of chronologic age, all preterm infants, regardless of initial birth weight or gestational age, are as likely to respond as adequately as do older and larger infants. Thus Hepatitis B vaccine should be given in preterm infants weighing < 2000 grams and born to HBsAg-negative mothers at 1 month of postnatal age if medically stable or at hospital discharge.

Side Effects: Side effects are generally mild, transientand confined to the site of injection (erythema, swelling, induration). Systemicreactions (fatigue, slight fever, headache, nausea, abdominal pain) are uncommon.

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