Hepavax-Gene® is a recombinant hepatitis B vaccine. Its immunogenic component, recombinant hepatitis B surface antigen (HbsAg), is produced in modified yeast using Crucell’s proprietary Hansenula polymorpha expression system. It is one of the WHO’s pre-qualified vaccines for active immunization against hepatitis B virus.
Hepatitis refers to inflammation of the liver. One of seven different human hepatitis viruses, hepatitis B (HBV) causes various complications if left untreated does as well when treated, treatment is a not an option comparable with prevention. It is the most serious type of viral hepatitis and the only type causing chronic hepatitis for which a vaccine is available.
Infection with HBV leads to one of three outcomes. An infected individual may: die of fulminant hepatitis within days or weeks after the onset of the disease; recover after symptomatic or asymptomatic infection and develop lifelong immunity against the disease; or develop chronic infection for which no specific treatment is available and which may ultimately cause death from cirrhosis of the liver or liver cancer.
It is estimated that 2 billion people have become infected with HBV globally, with 350 million being chronic carriers. The disease claims approximately 1 million lives each year. Young children who become infected with HBV are the most likely to develop chronic infection. About 90% of infants infected during the first year of life and 30% to 50% of children infected between 1 to 4 years of age develop chronic infection. For those who become chronically infected during childhood, the risk of death from HBV-related liver cancer or cirrhosis is approximately 25%.
HBV is highly infectious and is endemic in many parts of the world. In many parts of the developing world (sub-Saharan Africa, most of Asia, and the Pacific), most people become infected with HBV during childhood, with 8% to 10% of the general population becoming chronically infected. As a result, liver cancer caused by HBV is among the top three causes of death by cancer in men and women living in these regions.
Higher rates of chronic HBV infection are also found in the Amazon and the southern parts of Eastern and Central Europe. In the Middle East and Indian sub-continent, about 5% of the population are chronically infected. While one out of 20 people in the United States will get infected with HBV some time during their lives, infection is less common in Western Europe and North America, where less than 1% are chronically infected.
Transmission of HBV occurs as a result of the exchange of blood (for example, through the sharing of needles by intravenous drug users), the exchange of fluids during sexual intercourse, or the exchange of body fluids between an infected mother and a new-born baby during birth (perinatal transmission).
HBV infection can be asymptomatic, with the likelihood of symptoms increasing with age. Symptoms can include: yellow skin or yellowing of the whites of your eyes (jaundice); tiredness; loss of appetite; nausea; abdominal discomfort; dark urine; clay-colored bowel movements; and joint pain.
HBV vaccines have demonstrated excellent safety and efficacy since they became available in 1982. Since 1991, the WHO has called for all countries to add HBV vaccine into their national immunization programs.
Although the vaccine will not cure chronic hepatitis once it has taken hold, it is 95% effective in preventing chronic infections from developing and, as such, is considered to be the first vaccine against a major human cancer. Liver cancer, which usually develops between the ages of 35 and 65, is almost always fatal. In developing countries, most people with liver cancer will die within months of diagnosis. In wealthier societies, surgery and chemotherapy can prolong life, perhaps for a few years, and patients with cirrhosis sometimes benefit from liver transplants. Expensive drugs like interferon or lamivudine can help some patients with chronic hepatitis B. However, the prevention of this disease with a vaccine is clearly preferable to the difficult prospect of trying to cure it.
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