Hepatitis B virus (HBV) is the cause of significant disease worldwide. Acute infection occurs with hepatitis B, but chronic asymptomatic infection leading to chronic liver disease and hepatocellular carcinoma (HCC) is a life-long concern. Infections in infants and pre-school age children are at greatest risk of becoming chronic, thereby increasing the risk of cirrhosis and primary HCC later in life, which is probably due to the effect of age on the immune system's ability to clear and eliminate the infection. Treatment for hepatitis B is rarely effective with current medications.
Global burden of Hepatitis BGlobally, hepatitis B is one of the most common infectious diseases. Estimates indicate that atleast 2 billion people have been infected with HBV, with over 378 million people being chronic carriers (6% of the world population). Some 4.5 million new HBV infections occur worldwide each year and 15-40% of those infected will develop cirrhosis, liver failure or hepato-cellular carcinoma.
On the basis of sero-epidemiological surveys, the World Health Organization (WHO) has classified countries into three levels of endemicity according to the prevalence 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 childhood with perinatal transmission accounting for most chronic HBV infection.
Transmission of Hepatitis BThe 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 is 70-90% for those born to HBeAg-positive mothers and less than 15% for those born to HBeAg-negative mothers.
Prevention of Hepatitis BThe best approach to HBV control is prevention by vaccination and by screening of blood products and organ donors. Recombinant HBV vaccine is effective in 97% of at risk infants.
Hepatitis B vaccine
Hepatitis B vaccine consists of purified HBsAg particles produced through 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 being developed. These vaccines specifically
aim to enhance the immune response in
immunocompromised persons and non-responders.
Immunization against hepatitis B requires the intramuscular administration of three doses of vaccine given at 0, 1 and 6 months. More rapid protection (i.e. for healthcare workers exposed to HBV or the susceptible sexual partner of a patient with acute hepatitis B) can be achieved through the adoption of an accelerated schedule using three doses of vaccine administered at 0, 1 and 2 months followed by a booster dose given at 12 months.
Various Hepatitis B schedules recommended are:
Birth, 1 and 6 months
Birth, 6 and 14 weeks
6, 10 and 14 weeks
Birth, 6 weeks, 6 months
Birth, 6 weeks, 10 weeks, 14 weeks
DosingFor 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 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 anti-hepatitis B antibodies (anti-HBs) in 85% to 99% of recipients. People with immunodeficiencies, renal failure, have poorer response and higher dosages are recommended. Passive immunisation at birth with HBV immunoglobulins also required if the mother is HBeAg positive and vaccine is given in all cases at birth with 2 or 3 subsequent vaccinations over 6 months so that all exposed children should receive at least three doses.
Booster doses of hepatitis B vaccine
are not recommended for any age group; however the need for booster continues to be evaluated.
Delay in between dosesHepatitis B induces strong T cell response and memory. Anamnestic response occurs even when the anti-HBs 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 babiestudies 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 pre-term 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 pre-term infants weighing < 2000 grams and born to HBsAg-negative mothers at 1 month of post-natal age if medically stable or at hospital discharge.
Side-effectsare generally mild, transient and confined to the site of injection (erythema, swelling, induration). Systemic reactions (fatigue, slight fever, headache, nausea, abdominal pain) are uncommon.