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Letters to the Editor Indian Pediatrics 2001; 38: 1335-1338 |
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IAP Hepatitis B Immunization Schedule |
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Hepatitis B infection and its sequalae are important public health problems in India. Perinatal route is an important mode of transmission of the virus from carrier mothers to their newborn infants. The prevalence of HBsAg positivity in pregnant mothers in various Indian studies ranges from 0.6%-5.0%(1-3). In addition to perinatal transmis-sion, horizontal mode also contributes substantially to the pool of chronic infection. The principal objective of hepatitis B immunization and its sequelae is to prevent chronic HBV infection and its sequelae. Hepatitis B immunization strategies include a three-pronged attack: (i) routine infant vaccination; (ii) prevention of perinatal HBV transmission; (iii) catch-up vaccination of older age groups. Programmatically, it is usually easiest if the three doses of hepatits B vaccine are given at the same time as the three doses of DPT. Administering the vaccine earlier in life makes it easier to achieve high immunization coverage. This schedule prevents infections acquired during early childhood, which accounts for most of the HBV-related disease burden in countries with high endemicity. However, this schedule does not prevent perinatal HBV infections because it does not include a dose of hepatitis B vaccine at birth. The immunization schedule recommended by Expanded Program on Immunization in 1995, mentioned two options for both the situations (Table I)(4).
In countries where yellow fever poses a risk. ** Scheme A is recommended in countries where perinatal transmission of hepatitis B virus is frequent (e.g., South East Asia); Scheme B may be used in countries where perinatal transmission is less frequent (e.g., sub-Saharan Africa). Reproduced from(4). For preventing perinatal transmission the first dose of hepatitis B vaccine should be given as soon as possible after birth, preferably within 24 hours. In most countries the most feasible strategy for preventing perinatal hepatitis B transmission involves giving a dose of Hepatitis B vaccine to all infants at birth, as a program to screen HBV-infected mothers will require extensive resources. However, to give the first dose at birth, with the present health infrastructure and health care delivery system in India, is not feasible currently. In view of this difficulty, a high level of completion of hepatitis B vaccine series among all infants should be the highest priority. This is likely to have the greatest overall impact on the prevalence of chronic HBV infection in children, regardless of whether it is feasible to administer a dose, at birth. In order to achieve reduction of HBV carrier burden in a country, WHO also recommends catch up vaccination of older age group in addition to the other two strategies mentioned. The IAP Committee on Immunization has strongly recommended that the first dose of hepatitis B vaccine should be given as soon as possible after birth and especially within 24 hours. The second dose should be given along with DPT at 6 weeks and third dose at 14 weeks. For babies who are not available at birth, vaccination should not be denied. In this situation, the second schedule of 6,10 and14 weeks is recommended. Evidence from India also supports the seroprotective efficacy of the schedules recommended by the IAP Committee on Immunization(5,6) The recom-mendation also fits well with the existing EPI schedules. There is no current evidence to support the hypothesis that higher titers following vaccination with a particular schedule offer longer and extra protection from the disease. With the advent of combination vaccine, WHO has suggested an additional schedule with monovalent HepB vaccine at birth and DPT-HepB at 6, 10 and 14 weeks. This third option is to make the logistics simpler, which entails a higher cost of the fourth dose (Table II)(7). Individual countries may adapt the best schedule to fit into their immunization program. Basically the need is to give 3 doses of the vaccine at least 4 weeks apart and this should fit on the EPI system and local disease epidemiology.
* Only given in countries where polio is highly endemic; ** Monovalent vaccine; + Monovalent or combination vaccine; # Combination vaccine. Adapted from(7). As far as long term protection and booster doses are concerned. it has been shown that, children and adults, following 3 dose hepatitis schedule are protected from the disease for as long as 15 years. Even if protective antibody titer decline with time, long term protection relies on immunolgical memory, which allows a protective anamnestic response after exposure to HBV. Booster doses of vaccine are not, therefore recommended(7). A.K. Dutta, | |||||||||||||||||||||||||||||||||||||||||||||||||||||
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