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Hepatitis B vaccine

Vaccine against hepatitis B

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Engerix B (Hepatitis B) vaccine, showing pre-filled syringe
Whispyhistory · CC BY-SA 4.0

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Blood testing to verify that the vaccine has worked is recommended in those at high risk. Additional doses may be needed in people with poor immune function but are not necessary for most people. In those who have been exposed to the hepatitis B virus but not immunized, hepatitis B immune globulin should be given in addition to the vaccine. The vaccine is given by injection into a muscle.

Serious side effects from the hepatitis B vaccine are very uncommon. Pain may occur at the site of injection. It is safe for use during pregnancy or while breastfeeding. It has not been linked to Guillain–Barré syndrome. Hepatitis B vaccines are produced with recombinant DNA techniques and contain immunologic adjuvant. They are available both by themselves and in combination with other vaccines.

The first hepatitis B vaccine (Merck's Heptavax-B) was approved in the United States in 1981. A recombinant version (Merck's Recombivax-HB) came to market in 1986. It is on the World Health Organization's List of Essential Medicines. Both versions were developed by Maurice Hilleman and his team.

Medical uses

In the United States vaccination is recommended for nearly all babies at birth. Many countries routinely vaccinate infants against hepatitis B. In countries with high rates of hepatitis B infection, vaccination of newborns has not only reduced the risk of infection but has also led to a marked reduction in liver cancer. This was reported in Taiwan where the implementation of a nationwide hepatitis B vaccination program in 1984 was associated with a decline in the incidence of childhood hepatocellular carcinoma.

In the United Kingdom, the vaccine is given to all babies at birth and is also offered to people in various categories at higher risk, including men who have sex with men.

In many areas, vaccination against hepatitis B is also required for all health-care and laboratory staff. Both types of the vaccine, the plasma-derived vaccine and the recombinant vaccine, seem to be able to elicit similar protective anti-HBs levels.

The US Centers for Disease Control and Prevention (CDC) issued recommendations for vaccination against hepatitis B among people with diabetes. The World Health Organization (WHO) recommends a pentavalent vaccine, combining vaccines against diphtheria, tetanus, pertussis and Haemophilus influenzae type B with the vaccine against hepatitis B. There is not sufficient evidence on how effective this pentavalent vaccine is compared to the individual vaccines. A pentavalent vaccine combining vaccines against diphtheria, tetanus, pertussis, hepatitis B, and poliomyelitis is approved in the US and is recommended by the Advisory Committee on Immunization Practices.

Hepatitis B vaccination, hepatitis B immunoglobulin, and the combination of hepatitis B vaccine plus hepatitis B immunoglobulin, are all considered as preventive for babies born to mothers infected with hepatitis B virus. The combination is superior for protecting these infants. The effectiveness of being vaccinated during pregnancy to prevent vertical transmission of hepatitis B to infants has not been studied. Hepatitis B immunoglobulin before birth has not been well studied.

Effectiveness

Studies have found that that immune memory against HepB is sustained for at least 30 years after vaccination, and protects against clinical disease and chronic HepB infection, even in cases where anti-hepatitis B surface antigen (anti-Hbs) levels decline below detectable levels. Testing to confirm successful immunization or sustained immunity is not necessary or recommended for most people, but is recommended for infants born to a mother who tests positive for HBsAg or whose HBsAg status is not known; for healthcare and public safety workers; for immunocompromised people such as haemodialysis patients, HIV patients, haematopoietic stem cell transplant [HSCT] recipients, or people receiving chemotherapy; and for sexual partners of HBsAg-positive people.

An anti-Hbs antibody level above 100 mIU/ml is deemed adequate and occurs in about 85–90% of individuals. An antibody level between 10 and 100 mIU/ml is considered a poor response, and these people should receive a single booster vaccination at this time, but do not need further retesting. People who fail to respond (anti-Hbs antibody level below 10 mIU/ml) should be tested to exclude current or past hepatitis B infection, and given a repeat course of three vaccinations, followed by further retesting 1–4 months after the second course. Those who still do not respond to a second course of vaccination may respond to intradermal injection or to a high dose vaccine or to a double dose of a combined hepatitis A and B vaccine. Those who still fail to respond will require hepatitis B immunoglobulin (HBIG) if later exposed to the hepatitis B virus.

Poor responses are mostly associated with being over the age of 40 years, obesity, celiac disease, and tobacco smoking, and also in alcoholics, especially if with advanced liver disease. People who are immunosuppressed or on dialysis may not respond as well and require larger or more frequent doses of vaccine. At least one study suggests that hepatitis B vaccination is less effective in patients with HIV. The immune response to the hepatitis B vaccine can be impaired by the presence of parasitic infections such as helminthiasis.

The HepB vaccine is vital for use for infants who contract HepB. 90% of infants who contract HepB and do not receive the vaccination will develop chronic infection. These chronic hepatitis B virus infections are life-threatening, with a 15–25% risk of death from complications.

Duration of protection

The hepatitis B vaccine is believed to provide indefinite protection. Older literature assumed that immunity would wane with antibody titers and only effectively last five to seven years, but immune-challenge studies show that even after 30 years, the immune system maintains the ability to produce an anamnestic response, i.e. to rapidly bump up antibody levels when the previously seen antigen is detected. This shows that the immunological memory is not affected by the loss of antibody levels. As a result, subsequent antibody testing and administration of booster doses is not required in successfully vaccinated immunocompetent individuals. UK guidelines suggest that people who respond to the vaccine and are at risk of occupational exposure, such as for healthcare workers, a single booster is recommended five years after initial immunization.

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