Hepatitis B vaccine
Hepatitis B was previously referred to as "serum hepatitis" because it usually is spread by the transfer of infected blood or serum (for example, through needle sticks, blood transfusions, hemodialysis, and childbirth). Hepatitis B also is spread through sexual intercourse and may be passed from mother to child. Inadvertent exposure to infected blood or body fluids may occur during tattooing, body piercing, or when sharing razors or toothbrushes with an infected person. Persons infected with hepatitis B may be asymptomatic or may develop fatigue, jaundice, and weight loss. Rarely - though more commonly than with hepatitis A - acute infection with hepatitis B can cause liver failure and death.
Most infected adults are able to clear the hepatitis B virus from their body and become immune to further infections with hepatitis B. However, some people are not able to clear the hepatitis B virus and it progresses to chronic (persistent) infection and inflammation of the liver. Most infants infected at birth and 25% to 50% of infected children aged 1–5 years have chronic persistent infection.
Chronic infection may be mild or may damage the liver. The majority of individuals with chronic hepatitis B who clear the virus and are "cured" still have detectable virus in the liver. However, the importance of this fact is unclear since there is no evidence of consequences to the presence of the virus except that it can be reactivated with immunosuppression. Individuals with hepatitis B virus only in the liver are not infectious. Some people with chronic hepatitis B infection have their lives shortened by complications of liver disease, cirrhosis, or liver cancer.
Vaccination has reduced the number of new cases of hepatitis B by more than 75% in the United States. The hepatitis B vaccine contains a protein (antigen) that stimulates the body to make protective antibodies. Examples of hepatitis B vaccines available in the United States include hepatitis B vaccine-injection (Engerix-B and Recombivax-HB). Three doses (given at 0, 1, and 6 months) are necessary to assure protection.
There are also combination vaccines on the market that provide protection against hepatitis B and other diseases. For example:
Hepatitis B vaccines are effective and safe. Most vaccinated individuals develop protective antibodies when they get the vaccine and are protected from infection with hepatitis B. Among individuals at high risk for infection with hepatitis B include:
- health care workers,
- intimate and household contacts of patients with chronic hepatitis B infection,
- public safety workers who may be exposed to blood products,
- men who have sex with men,
- individuals with multiple sexual partners,
- dialysis patients,
- injection drug users,
- persons with chronic liver disease,
- residents and staff in institutions that care for persons with developmental disabilities,
- persons infected with human immunodeficiency virus (HIV), and
- persons who require repeated transfusions or blood products.
Centers that serve high-risk individuals are encouraged to provide the vaccine to their clients. Such centers include:
A blood test for hepatitis B antibodies is recommended after vaccination to ensure that antibodies have been produced. For the few who do not form antibodies, revaccination may improve the response, especially in infants. However, a small proportion of individuals will never respond to hepatitis B vaccination. Side effects from the vaccine usually are mild, primarily soreness at the site of injection. The risk of serious allergic reactions (anaphylaxis) is less than one per million doses.
In the United States, hepatitis B vaccination is recommended for all infants at birth. Older children and adolescents should receive the vaccine if they did not receive it at birth. Adults in high risk situations also are advised to receive hepatitis B vaccine.
Some countries have a high prevalence of hepatitis B in their population. Travelers who visit these countries for a prolonged period of time (usually 6 months or longer) and those who may be exposed to blood or semen should consider vaccination.
Unvaccinated individuals who are exposed to a known case of hepatitis B or to a person at high risk for hepatitis B should be evaluated by a physician. Examples of such exposures include needle stick injuries in health care workers or sexual intercourse with an infected person. If the exposure is significant, the physician will recommend vaccination and may also recommend an injection of hepatitis B immune globulin (HBIG). HBIG is prepared from the plasma of blood donors and contains antibodies to hepatitis B. Vaccination and HBIG can substantially reduce the risk of disease in persons exposed to hepatitis B if given within one week of a needle stick or two weeks of sexual intercourse.
Vaccination provides long-term immunity in people who respond to the vaccine. There is no need for HBIG if an exposure occurs to a vaccinated person who is known to have responded to the vaccine; however, a blood test might be drawn to verify that the person did respond to the vaccine and form antibodies.
Infected mothers can pass hepatitis B to their newborn infants. All pregnant women should have blood drawn to determine if they are infected. Infants born to infected mothers should receive HBIG and hepatitis B vaccine at birth. This is 85% to 95% effective in eliminating the risk of hepatitis B infection in the infant.