vaccination, while Twinrix (GlaxoSmithKline) is used for adult vaccination (CDC, 2005). Comvax is a bivalent vaccine designed to prevent Hae-mophilus influenzae type B infection in addition to hepatitis B and contains Haemophilus influenzae type B capsular polysaccharide polyribosylribitol phosphate affixed to Neisseria meningitides outer-membrane protein complex and HBsAg from recombinant yeast cultures (CDC, 2005). Pediarix contains recombinant HBsAg, diphtheria and tetanus toxoids and acellular pertussis adsorbed (DTaP), and inactivated poliovirus (CDC, 2005). Twinrix is designed to prevent hepatitis A and B, and contains recombinant HBsAg and inactivated hepatitis A virus (CDC, 2005).
The Advisory Committee on Immunization Practices, the American Academy of Pediatrics, and the American Academy of Family Physicians recommend the HBV vaccine in a series of three doses: at birth, between 1 and 2 months, and between 6 and 18 months (CDC, 1991; Mast and Ward, 2008). In unvaccinated adolescents and adults, the CDC recommends three doses of the vaccine with the first and second dose 1 month apart and the third dose 6 months after the initial dose (CDC, 1991). The three-dose series results in protective concentrations of HBsAg antibodies in more than 95 percent of healthy infants, children, and adolescents and in greater than 90 percent of healthy adults aged up to 40 years (Mast and Ward, 2008). In adults older than 40 years, immunogenicity drops below 90 percent (Mast and Ward, 2008). The hepatitis B vaccine has a preexposure efficacy of 80–100 percent, and if given in conjunction with hepatitis B immune globulin, the vaccine is 85–95 percent effective in preventing chronic infection post-HBV exposure (Mast and Ward, 2008). Following vaccination, HBV immunity appears to be lifelong, and booster doses of the vaccine are not routinely recommended (Mast and Ward, 2008). In 2009, 92 percent of U.S. children aged 19–35 months completed all three recommended doses of hepatitis B vaccine (CDC, 2010).
No studies were identified in the literature for the committee to evaluate the risk of encephalitis or encephalopathy after the administration of hepatitis B vaccine.
Weight of Epidemiologic Evidence
The epidemiologic evidence is insufficient or absent to assess an association between hepatitis B vaccine and encephalitis or encephalopathy.