Hepatitis B vaccine is a vaccine that prevents hepatitis B. The first dose is recommended within 24 hours of birth with either two or three more doses given after that. This includes those with poor immune function such as from HIV/AIDS and those born premature. It is also recommended for health-care workers to be vaccinated. In healthy people routine immunization results in more than 95% of people being protected.
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. The current vaccines are produced with recombinant DNA techniques. They are available both by themselves and in combination with other vaccines.
The first hepatitis B vaccine was approved in the United States in 1981. A recombinant version came to market in 1986. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. As of 2014, the wholesale cost in the developing world is US$0.58-13.20 per dose. In the United States it costs US$50-100.
Video Hepatitis B vaccine
Medical uses
Hepatitis B vaccination, hepatitis B immunoglobulin, and the combination of hepatitis B vaccine plus hepatitis B immunoglobulin, all are considered as preventive for babies born to mothers infected with HBV. The combination is superior for protecting these infants. The vaccine during pregnancy is not considered to be valuable in protecting babies of the infected mothers. Hepatitis B immunoglobulin before birth has not been well studied.
In the United States vaccination is recommended for nearly all babies at birth. Many countries now 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 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 UK, the vaccine is offered to MSM, usually as part of a sexual health check-up. A similar situation is in operation in Ireland.
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 (PDV) and recombinant vaccine (RV), seems to be able to elicit similar protective anti-HBs levels.
The Centers for Disease Control and Prevention have issued recommendations for vaccination against hepatitis B among patients with diabetes mellitus. The World Health Organization recommends a pentavalent vaccine, combining vaccines against diphtheria, tetanus, pertussis and Haemophilus influenzae type B with the vaccine against hepatitis B. There is not yet sufficient evidence on how effective this pentavalent vaccine is in relation to the individual vaccines.
Effectiveness
Following the primary course of 3 vaccinations, a blood test may be taken after an interval of 1-4 months to establish if there has been an adequate response, which is defined as an anti-hepatitis B surface antigen (anti-Hbs) antibody level above 100 mIU/ml. Such a full response 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 3 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 administration 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 and smoking, and also in alcoholics, especially if with advanced liver disease. Patients who are immunosuppressed or on renal dialysis may respond less 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.
Duration of protection
It is now believed that the hepatitis B vaccine provides indefinite protection. However, it was previously believed and suggested that the vaccination would only provide effective cover of between five and seven years, but subsequently it has been appreciated that long-term immunity derives from immunological memory which outlasts the loss of antibody levels and hence subsequent testing and administration of booster doses is not required in successfully vaccinated immunocompetent individuals. Hence with the passage of time and longer experience, protection has been shown for at least 25 years in those who showed an adequate initial response to the primary course of vaccinations, and UK guidelines now suggest that for initial responders who require ongoing protection, such as for healthcare workers, only a single booster is advocated at 5 years.
Maps Hepatitis B vaccine
Side effects
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.
Multiple sclerosis
Several studies have looked for an association between recombinant hepatitis B vaccine (HBV) and multiple sclerosis (MS) in adults. Most studies do not support a causal relationship between hepatitis B vaccination and demyelinating diseases such as MS. A 2004 study reported a significant increase in risk within 3 years of vaccination. Some of these studies were criticized for methodological problems. This controversy created public misgivings about HB vaccination, and hepatitis B vaccination in children remained low in several countries. A 2006 study concluded that evidence did not support an association between HB vaccination and sudden infant death syndrome, chronic fatigue syndrome, or multiple sclerosis. A 2007 study found that the vaccination does not seem to increase the risk of a first episode of MS in childhood.
Usage
The following is a list of countries by the percentage of infants receiving three doses of hepatitis B vaccine as published by the World Health Organization in 2014.
History
The road to the hepatitis B vaccine began in 1963 when American physician/geneticist Baruch Blumberg discovered what he called the "Australia Antigen" (now called HBsAg) in the serum of an Australian Aboriginal person. In 1968, this protein was found to be part of the virus that causes "serum hepatitis" (hepatitis B) by virologist Alfred Prince. The American microbiologist/vaccinologist Maurice Hilleman at Merck used three treatments (pepsin, urea and formaldehyde) of blood serum together with rigorous filtration to yield a product that could be used as a safe vaccine. Hilleman hypothesized that he could make an HBV vaccine by injecting patients with hepatitis B surface protein. In theory, this would be very safe, as these excess surface proteins lacked infectious viral DNA. The immune system, recognizing the surface proteins as foreign, would manufacture specially shaped antibodies, custom-made to bind to, and destroy, these proteins. Then, in the future, if the patient were infected with HBV, the immune system could promptly deploy protective antibodies, destroying the viruses before they could do any harm.
Hilleman collected blood from gay men and intravenous drug users--groups known to be at risk for viral hepatitis. This was in the late 1970s, when HIV was yet unknown to medicine. In addition to the sought-after hepatitis B surface proteins, the blood samples likely contained HIV. Hilleman devised a multistep process to purify this blood so that only the hepatitis B surface proteins remained. Every known virus was killed by this process, and Hilleman was confident that the vaccine was safe.
The first large-scale trials for the blood-derived vaccine were performed on gay men, in accordance with their high-risk status. Later, Hilleman's vaccine was falsely blamed for igniting the AIDS epidemic. (See Wolf Szmuness) But, although the purified blood vaccine seemed questionable, it was determined to have indeed been free of HIV. The purification process had destroyed all viruses--including HIV. The vaccine was approved in 1981.
The blood-derived hepatitis B vaccine was withdrawn from the marketplace in 1986 when Pablo DT Valenzuela, Research Director of Chiron Corporation, succeeded in making the antigen in yeast and invented the world's first recombinant vaccine. The recombinant vaccine was developed by inserting the HBV gene that codes for the surface protein into the yeast Saccharomyces cerevisiae. This allows the yeast to produce only the noninfectious surface protein, without any danger of introducing actual viral DNA into the final product. This is the vaccine still in use today.
In 1976, Blumberg had won the Nobel Prize in Physiology or Medicine for his work on hepatitis B (sharing it with Daniel Carleton Gajdusek for his work on kuru). In 2002, Blumberg published a book, Hepatitis B: The Hunt for a Killer Virus. In the book, according to Paul A. Offit--Hilleman's biographer and an accomplished vaccinologist himself--Blumberg...
... claimed that the hepatitis B vaccine was his invention. Maurice Hilleman's name is mentioned once.... Blumberg failed to mention that it was Hilleman who had figured out how to inactivate hepatitis B virus, how to kill all other possible contaminating viruses, how to completely remove every other protein found in human blood, and how to do all of this while retaining the structural integrity of the surface protein. Blumberg had identified Australia antigen, an important first step. But all of the other steps--the ones critical to making a vaccine--belonged to Hilleman. Later, Hilleman recalled, "I think that [Blumberg] deserves a lot of credit, but he doesn't want to give credit to the other guy."
Manufacture
The vaccine contains one of the viral envelope proteins, hepatitis B surface antigen (HBsAg). It is now produced by yeast cells, into which the genetic code for HBsAg has been inserted. Afterward an immune system antibody to HBsAg is established in the bloodstream. The antibody is known as anti-HBs. This antibody and immune system memory then provide immunity to HBV infection.
Brand names
The common brands available are Recombivax HB (Merck), Engerix-B (GSK), Elovac B (Human Biologicals Institute, a division of Indian Immunologicals Limited), Genevac B (Serum Institute), Shanvac B, etc. These vaccines are given by the intramuscular route. In late 2017 the FDA approved a new vaccine called Heplisav-B from Dynavax Technologies Corps. This two-dose vaccine will compete with Engerix-B's three-dose vaccine.
Twinrix is a vaccine against hepatitis A and hepatitis B.
Research
Injectable Hepatitis B vaccines require expensive production processes and refrigeration, which can make them difficult to access in developing countries. As a result, researchers have been working to engineer plants capable of producing the ingredients necessary to make vaccines so that people can eat these plants to receive the vaccine. Potatoes, bananas, lettuce, carrots, tobacco are some of the plants being genetically engineered to produce the Hepatitis B vaccine ingredients.
The process of genetically engineering plants to produce the vaccine includes extracting the gene that codes for Hepatitis B surface antigens from the Hepatitis B genome, and placing it in a bacterial plasmid. The bacteria then infect a plant, which will produce the surface antigens. When a human eats the plant, their body is stimulated to produce an antibody response to the surface antigens. Although concerns remain in improving the efficacy of edible vaccines, controlling the dosage of vaccine in each plant, and managing land allocation for this process, scientists consider this a promising avenue for vaccinating underprivileged areas of the world.
References
External links
Source of the article : Wikipedia
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