Hepatitis V virus (HBV) is spread is vertically, from mother to child. Combine this with the fact that age is inversely proportional to the risk of becoming a chronic carrier of HBV and neonates are a significantly affected population. This poses a threat that not only will the baby develop liver problems, but as a chronic carrier also has a significant chance of passing the virus on to others horizontally. In fact, about 25% of neonates infected by their mothers at such a young age will develop liver failure or liver cancer. One-third of all chronic cases of HBV come from individuals affected as infants or young children. Because of these risks, it is especially important to take measures to prevent infection in neonates. In order to do so, it is recommended that all pregnant women be tested for HBV by the presence of Hepatitis B surface antigen (HBsAg) in their serum. If a mother is positive for serum HBsAg, her infant not only receives the standard vaccine, but within the first 12 hours after birth receives pre-formed anti-HBsAg antibody (immunoglobulin) in a form of passive immunization in addition to receiving the first dose of the standard recombinant vaccine. The second and third doses of the standard vaccine should be administered to these children on schedule, and in endemic parts of the world, a fourth dose is recommended at 12 months of age (6 months after the third dose). Thus, infants need to be vaccinated immediately in any case, and given immunoglobulin in addition if they are born to sero-positive mothers. See our vaccine page or epidemiology page for more information. 2, 4, 19, 22


Originally, the common version of the HBV vaccine found in the US contained a substance called thimerosal as a preservative. Thimerosal is an anti-bacterial preservative containing a small amount of mercury, a substance that can be highly toxic to humans at certain levels. Thimerosal was included in the vaccine in order to prevent bacteria and other organisms from contaminating the vaccine, especially in multi-dose, open vials. In fact, it has been used as a preservative in many types of vaccines since the 1960's. Because the HBV vaccine was given to neonates less than one month old, the concern about the mercury present in thimerosal was significant. The recommendation for the age of the first dosage of the HBV vaccine was pushed back in the United States form birth to 2-6 months of age, provided the mother was sero-negative for HBsAg. It is important to stress that although there was concern about the mercury present in the thimerosal, there is no evidence of harm to neonates due to mercury exposure as a result of the vaccine. Recently, however, HBV vaccine without thimerosal became available for use from Merck. At first, the thiomerosal free vaccine was only availibile in limited quantities, but in September 1999 it became available on a large scale. Thus, the recommendation for vaccination of infants was again to give the first dose of the vaccine at birth. In areas where the thimerosal-free vaccine was (or in some places, still is) unavailable, the recommendation was to wait until the infant was a little older and larger to begin the vaccine series unless the mother was sero-positive for HBsAg or her HBsAg status was unknown. In those cases, the vaccine was to be given immediately, as it has not been shown that the mercury has caused any problems in the neonates who were exposed to it. See our vaccine page for more information. www.psigroup.com, www.immunize.org, www.cdc.gov, www.merck.com, www.who.int

 

Another issue relating to the to distribution of the vaccine is its stability. Similar to many other vaccines, such as DTP, the hepatitis B vaccine needs what is known as a "cold chain," or a system of delivery that is designed to keep the vaccine cold (between 2 and 8 degrees Celsius) at all times through its journey from manufacturer to recipient. When the vaccine is being shipped to the developing world, it is often difficult to ensure the cold chain. Once at its final destination, the vaccine must be kept cold until it is administered, and many outlying areas do not have the resources to do so. Although this poses a significant distribution problem, the problem may not be as severe as originally thought because the vaccine has actually been shown to be fairly heat stable. After being at a temperature of 45 C for one week or 37 C for an entire month, the vaccine's immunogenicity and efficacy are not altered. The thermodynamic stability of the vaccine, therefore, may allow it to be given anywhere in the developing world or at birth by midwives and other trained workers who deliver babies away from any source of refrigeration. For more information, see our vaccine page and epidemiology page. 19

 

Because of the burden of HBV disease in the developing world, it is essential that these populations get vaccinated against hepatitis B virus. However, it is these same populations who have the least access to the vaccine. The primary reason is cost. One dose of the vaccine can cost approximately US$30-$55, bringing the three-dose cost to upwards of US$100-$150. Unfortunately, this is far too expensive for many countries in the developing world who spend about US$12 or less per capita per year for all organized health care. Therefore, even though the World Health Organization (WHO) recommends that the HBV vaccine be added to the Expanded Programme of Immunization, many countries have been unable to do so. Thus far, about 100 countries have implemented this strategy, and more will probably do so once they become financially able. According to the World Health Organization, the cost of the vaccine itself is the largest worldwide problem with respect to universal vaccination. Therefore, the world's poorest nations are still not using the vaccine to protect children in areas of high endemicity. The children in these countries are unprotected and are at the highest risk for becoming chronic carriers, spreading the infection, and continuing the cycle of disease. For more information, see our vaccine page and future vaccine page. www.who.int, 5



At one point in time, there was concern that HBV vaccine was causing multiple sclerosis (MS), a debilitating disease of the central nervous system. However, several large epidemiological trials have not been able to find a link between the HBV vaccine and MS. At the current time, scientific knowledge cannot show any increased risk of MS associated with any of the HBV vaccines. www.immunize.org, www.hepnet.com, www.cdc.gov

 

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 The Vaccine

The Vaccine Future

 Vaccine Issues

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