Chronic Hepatitis B Infection

Hepatitis B is a disease of the liver caused by the hepatitis B virus (“HBV”), characterized by hepatic (e.g. liver) inflammation, injury, and even cell death. The disease can present acutely, and resolve on its own, or can progress to a chronic state.

Acutely, HBV infection can lead to fever, fatigue, malaise, abdominal pain, and hepatomegaly (abnormal enlargement of the liver). Often hepatitis B resolves on its own, but if the acute infection is not cleared by the immune system, the patient may develop chronic disease.

Chronic hepatitis B can lead to cirrhosis, scarring of the liver that leads to a number of physical and metabolic symptoms, including chronic liver failure. Chronic hepatitis B can also lead to hepatocellular carcinoma (“HCC”), the most common type of liver cancer and one of the three most common causes of cancer mortality in the world; chronic hepatitis B increases the risk of HCC by more than 100-fold.

There are more than two billion individuals with serological evidence of HBV infection worldwide. Of these, 240 million are chronic carriers and approximately 780,000 hepatitis B-related deaths occur annually. Despite advances in antiviral therapy, only a minority of patients with chronic hepatitis B will have a sustained immune response to treatment. Therefore, primary prevention by vaccination is considered the ideal way to control HBV.

First- and Second-Generation Hepatitis B Vaccines

The development of the hepatitis B vaccine is considered to be one of the major achievements of modern medicine. The first hepatitis B vaccine was licensed in 1981. This first-generation vaccine was prepared by removing plasma from HBV carriers and concentrating out a surface antigen (the S antigen). Derivation from plasma left concerns regarding the potential to transmit blood-borne infections, and therefore a second-generation of yeast-derived vaccines was created in the mid-1980s. These second-generation vaccines also contain the S antigen and are currently used for the universal vaccination of newborns and adults in many countries worldwide.

Successful seroprotection (the body’s ability to produce an antibody response capable of preventing an infection) against HBV infection is defined by rate and by an anti-HBV surface antibody (anti-HBs) titer of ≥ 10 mIU/ml following immunization. Second-generation hepatitis B vaccines have been shown to have good efficacy in neonates and in otherwise healthy individuals up to age 40. However, many individuals do not respond to currently marketed hepatitis B vaccines due to immunosenescence (the gradual deterioration of the immune system brought on by aging) or immunosuppression.

Hepatitis B vaccine failure is often explained by certain conditions such as smoking and obesity, and by comorbidities such as advanced age, renal failure, diabetes, and other immunosuppression. Genetically determined resistance may also play a factor in non-responsiveness.

Sci-B-Vac®: A Third-Generation Hepatitis B Vaccine

In contrast to second-generation hepatitis B vaccines, Sci-B-Vac® contains not only the S antigen from the hepatitis B virus, but also two additional surface antigens, the pre-S1 and pre-S2 surface antigens. By mimicking all three surface antigens of the hepatitis B virus, Sci-B-Vac® may provide more opportunities for the immune system to respond with antibodies to the virus, helping it to overcome some limitations of prior hepatitis B vaccines, which present only the S antigen.

To date, 20+ clinical studies have been completed in over 3,000 persons immunized with Sci-B-Vac®. This research has demonstrated that the vaccine can reliably, and safely, be used to prevent HBV infection. Some early studies of Sci-B-Vac® suggest that, in comparison to second-generation hepatitis B vaccines, a majority of individuals receiving Sci-B-Vac®, including neonates, children, and young adults, develop earlier seroprotection against HBV.

Moreover, anti-HBV antibody concentrations were found to be higher in a large percentage of vaccinated individuals and an immune response could be elicited by Sci-B-Vac® using a lower dosage than second-generation hepatitis B vaccines.

Researchers have also sought to understand how Sci-B-Vac® may benefit persons that are less likely to respond to currently marketed second-generation vaccines, including:

  • Elderly Persons: The immune system becomes less effective as individuals age. Aging is associated with increased susceptibility to infectious diseases, reduced response to vaccination, and an increased risk of developing severe or complicated illnesses as a result of infection. The impaired response to vaccination is due to accumulating functional defects at multiple levels of the immune system, which lower the overall magnitude and quantity of response to vaccination. Although safe, there is an age-specific decline in immune responsiveness to some currently marketed hepatitis B vaccines starting around age 40.
  • Persons with End-Stage Renal Disease: Chronic kidney disease is a condition where the kidneys are damaged and cannot filter blood as well as healthy kidneys. This lack of filtration leads to excess waste buildup in the body that can cause other health problems. Without treatment, diseased kidneys may stop working after a time, a condition called kidney failure or end-stage renal disease (“ESRD”). Currently marketed hepatitis B vaccine options may provide limited seroprotection to persons with ESRD.
  • Persons with Diabetes: Diabetes is a condition in which a person has a chronically high blood sugar level, due to an inability to absorb sugar and use it as energy. High blood sugar levels can lead to a number of complications including kidney failure, blindness, nerve damage, cardiovascular disease, and non-traumatic amputation. Persons with diabetes are less responsive to hepatitis B vaccines than healthy adults.

In addition, because of their contact with patients and/or infectious materials, many healthcare workers are at an increased risk of being exposed to HBV. The U.S. Advisory Committee on Immunization Practices (“ACIP”) recommends that all healthcare workers at risk of acquiring or transmitting HBV be vaccinated. Compared to some currently marketed hepatitis B vaccines, Sci-B-Vac® may offer faster seroprotection, potentially reducing the risk of infection.

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