Hepatitis, Viral, Type B - Article
Article: Hepatitis, Viral, Type B
Hepatitis B is caused by the hepatitis B virus (HBV). The clinical manifestations of HBV infection range in severity from no symptoms to fulminant hepatitis. Signs and symptoms of hepatitis B may include fever, malaise, anorexia, nausea, and abdominal discomfort, followed within a few days by jaundice.
HBV is transmitted through activities that involve contact with blood or blood-derived fluids. Such activities can include unprotected sex with an HBV-infected partner; injection of illegal drugs; work in health-care fields (medical, dental, laboratory, or other) that entail direct exposure to human blood; receiving blood transfusions that have not been screened for HBV; or having dental, medical, or cosmetic (e.g., tattooing or body piercing) procedures with needles or other equipment that are contaminated with HBV. In addition, open skin lesions, such as those due to impetigo, scabies, or scratched insect bites, can play a role in HBV transmission if direct exposure to wound exudates from HBV-infected persons occurs.
The prevalence of chronic HBV infection is low (<2%) in the general population in Northern and Western Europe, North America, Australia, New Zealand, Mexico, and Southern South America. In the United States and many other developed countries, children and adolescents are routinely vaccinated against hepatitis B. The highest incidence of disease is in younger adults, and most HBV infections are acquired through unprotected sex with HBV-infected partners or through illicit injection drug use. The prevalence of chronic HBV infection is intermediate (2%–7%) in South Central and Southwest Asia, Israel, Japan, Eastern and Southern Europe, Russia, most areas surrounding the Amazon River basin, Honduras, and Guatemala. The prevalence of chronic HBV infection is high (>8%) in all socioeconomic groups in certain areas: all of Africa; Southeast Asia, including China, Korea, Indonesia, and the Philippines; the Middle East, except Israel; south and Western Pacific islands; the interior Amazon River basin; and certain parts of the Caribbean (Haiti and the Dominican Republic).
Risk for Travelers
The risk of HBV infection for international travelers is generally low, except for certain travelers in countries where the prevalence of chronic HBV infection is high or intermediate. Factors to consider in assessing risk include 1) the prevalence of chronic HBV infection in the local population, 2) the extent of direct contact with blood or secretions, or of sex contact with potentially infected persons, and 3) the duration of travel. Modes of HBV transmission in areas with high or intermediate prevalence of chronic HBV infection that are important for travelers to consider are contaminated injection and other equipment used for health care-related procedures and blood transfusions from unscreened donors. However, unprotected sex and sharing illegal drug injection equipment are also risks for HBV infection in these areas.
The incubation period of hepatitis B averages 120 days (range 45–160 days). Constitutional symptoms such as malaise and anorexia may precede jaundice by 1–2 weeks. Clinical symptoms and signs include nausea, vomiting, abdominal pain, and jaundice. Skin rashes, joint pains, and arthritis may occur. The case-fatality rate is approximately 1%. Acute HBV infection causes chronic (long-term) infection in 30%–90% of persons infected as infants or children and in 6%–10% of adolescents and adults. Chronic infection can lead to chronic liver disease, liver scarring (cirrhosis), and liver cancer.
Hepatitis B vaccination should be administered to travelers to areas with intermediate to high levels of endemic HBV transmission (i.e., with hepatitis B surface antigen [HBsAg] prevalence >2%) and who will have close contact with the local populations. In particular, travelers who anticipate sex contact or who will have daily physical contact with the local population; or who are likely to seek medical, dental, or other treatment in local facilities; or any combination of these activities during their stay should be advised to receive the vaccine. Hepatitis B vaccination is currently recommended for all United States residents who work in health-care fields (medical, dental, laboratory, or other) that entail exposure to human blood.
Two monovalent hepatitis B vaccines are currently licensed in the United States: Recombivax HB, manufactured Merck and Co., Inc., and Engerix B, manufactured by GlaxoSmithKline. These vaccines are produced through recombinant DNA technology by baker's yeast into which the gene for HBsAg has been inserted. The usual schedule of primary vaccination consists of three intramuscular doses of vaccine. The recommended dose varies by product and the recipient's age (
Twinrix, manufactured by GlaxoSmithKline, is a combined hepatitis A and hepatitis B vaccine licensed for persons 18 years of age or more. Primary immunization consists of three doses, given on a 0-, 1-, and 6- month schedule, the same schedule as that used for single-antigen hepatitis B vaccine (Table 3–6). Twinrix consists of inactivated hepatitis A virus and recombinant HBsAg protein, with aluminum phosphate and aluminum hydroxide as adjuvant and 2-phenoxyethanol as a preservative.
Individual clinicians may choose to use an accelerated schedule (i.e., doses at days 0, 7, and 14) for travelers who will depart before an approved vaccination schedule can be completed. The FDA has not approved accelerated schedules that involve vaccination at more than one time during a single month for hepatitis B vaccines currently licensed in the United States. Persons who receive a vaccination on an accelerated schedule that is not FDA approved should also receive a booster dose at least 6 months after the start of the series to promote long-term immunity.
Hepatitis B vaccines have been shown to be very safe for persons of all ages. Pain at the injection site (3%–29%) and elevated temperature >37.7° C (>99.9° F) (1%–6%) are the most frequently reported side effects among vaccine recipients. In placebo-controlled studies, these side effects were reported no more frequently among persons receiving hepatitis B vaccine than among those receiving placebo. Among children receiving both hepatitis B vaccine and diphtheria-tetanus-pertussis (DTP) vaccine, these mild side effects have been observed no more frequently than among children receiving DTP vaccine alone. For hepatitis A vaccine (a component of the combination hepatitis A/hepatitis B vaccine Twinrix), the most frequently reported adverse reactions occurring within 3–5 days were soreness or pain at the injection site (56% among adults and 8% among children) and headache (14% among adults and 4% among children). No serious adverse events among children or adults that could be definitively attributed to hepatitis A vaccine or increases in serious adverse events among vaccinated persons compared with baseline rates have been identified.
Precautions and Contraindications
These vaccines should not be administered to persons with a history of hypersensitivity to any vaccine component, including yeast. The vaccine contains a recombinant protein (HBsAg) that is noninfectious. Limited data indicate that there is no apparent risk of adverse events to the developing fetus when hepatitis B vaccine is administered to pregnant women. HBV infection affecting a pregnant woman can result in serious disease for the mother and chronic infection for the newborn. Neither pregnancy nor lactation should be considered a contraindication for vaccination.
Source: Centers for Disease Control and Prevention
Cache Date: December 29, 2004
- Add Hepatitis B Vaccination to Your Back to School List (National Center for Infectious Diseases, CDC, OPHS, HHS)
- Advice for Parents (Hepatitis B Foundation)