What is Immunisation for hepatitis B?

 

Immunization for hepatitis B is a critical and highly effective public health intervention aimed at preventing infection with the hepatitis B virus (HBV). This immunization strategy primarily involves the administration of a hepatitis B vaccine, which stimulates the body's immune system to produce antibodies alongside the virus. In this comprehensive discussion, we will delve into the various aspects of hepatitis B immunization, including the need for vaccination, the vaccine's components, dosing schedules, effectiveness, safety, and the impact of immunization on the global burden of hepatitis B.

The Need for Hepatitis B Immunization

Hepatitis B is a significant global health concern, with approximately 257 million people living with chronic HBV infection worldwide. This viral infection can lead to severe liver-related complications, such as cirrhosis and liver cancer, resulting in substantial morbidity and mortality. HBV is transmitted through exchange with infected blood and body fluids, making it particularly dangerous for healthcare workers, people living with an infected individual, and individuals engaging in high-risk behaviors such as unprotected sex and intravenous drug use.

Hepatitis B immunization is crucial because it offers a primary means of preventing new infections and reducing the long-term health and economic burdens associated with the disease. By vaccinating individuals against HBV, we can significantly reduce the risk of transmission and help break the chain of infection.

The Hepatitis B Vaccine

The hepatitis B vaccine is a recombinant vaccine, meaning it is made from a non-infectious component of the virus. It does not contain live or inactivated HBV, making it a safe and highly effective preventive tool. The primary component of the vaccine is the hepatitis B shallow antigen (HBsAg), which is a protein on the virus's surface.

Vaccine Components

The hepatitis B vaccine consists of the following components:

Hepatitis B surface antigen (HBsAg): This is the key protein used to stimulate the immune response. It is derived from genetically modified yeast cells or mammalian cell cultures.

Adjuvants: These are substances added to enhance the body's immune response to the vaccine. Aluminum salts are commonly used adjuvants in the hepatitis B vaccine.

Vaccine Types

There are different types of hepatitis B vaccines available, including:

Engerix-B and Recombivax HB: These are standard recombinant vaccines that are typically given as three doses.

Heplisav-B: This is a newer, two-dose vaccine with a higher concentration of HBsAg and a different adjuvant (cytokine).

Pediatric vaccines: Special formulations are available for infants and children to ensure that they receive the appropriate dose for their age and weight.

Dosing Schedules

The hepatitis B vaccine is administered through a series of injections to stimulate a robust immune response. The dosing programme may vary depending on the specific vaccine product and the age of the recipient:

Standard Adult Dosing: Engerix-B and Recombivax HB are typically administered as a series of three doses. The another dose is given one month after the first, and the third dose is given six months after the first.

Heplisav-B: This vaccine offers a more accelerated dosing schedule, with just two doses given one month apart.

Pediatric Dosing: Infants are usually vaccinated with a 3-dose series, with the first dose given shortly after birth, followed by doses at one and six months of age.

Catch-Up Vaccination: People who missed childhood vaccination can receive the hepatitis B vaccine at any age, with a standard three-dose schedule.

Accelerated Schedules: In cases where rapid protection is needed, healthcare professionals may administer an accelerated schedule. For example, the second and third doses can be given one month and two months after the first dose, respectively.

Effectiveness and Immunity

The hepatitis B vaccine is very much effective in providing protection against HBV infection. After completing the recommended vaccine series, the vast majority of individuals develop immunity against the virus. The vaccine's efficacy is notably high:

Primary Vaccination: After completing the initial series, over 90% of recipients develop protective antibody levels.

Long-lasting Immunity: The vaccine induces long-lasting immunity, with protective antibodies persisting in the bloodstream for many years, if not a lifetime.

Reduced Risk of Infection: Vaccinated individuals are at a significantly reduced risk of contracting hepatitis B, even if they are exposed to the virus.

Preventing Chronic Infection: Immunization in infancy has been particularly effective in preventing chronic HBV infection, which is a major risk factor for liver disease.

Preventing Transmission: By reducing the number of individuals with chronic infection, the vaccine also helps reduce the risk of transmission within communities.

Safety and Side Effects

Hepatitis B vaccination is generally considered safe, with the benefits of preventing HBV infection far outweighing the risks associated with vaccination. Common side effects of the vaccine are mild and short-lived, including pain at the injection site, fever, and fatigue.

Serious allergic reactions to the vaccine are extremely rare. The vaccine is contraindicated only in individuals with a known severe affected reaction to a previous dose or to a vaccine component. It is important to discuss any known allergies with healthcare providers before vaccination.

Impact of Hepatitis B Immunization

The introduction of hepatitis B immunization has had a profound impact on the global burden of the disease:

Reduced Incidence: In countries with robust vaccination programs, there has been a substantial reduction in new hepatitis B cases, especially among children.

Prevention of Chronic Infection: Hepatitis B vaccination, particularly when administered at birth, has been effective in preventing chronic infection and its associated long-term health consequences.

Improved Health Outcomes: Vaccination has led to fewer cases of liver cirrhosis and liver cancer, resulting in improved public health and reduced healthcare costs.

Health Equity: Hepatitis B vaccination campaigns have helped address health disparities, as they are often targeted at high-risk populations, including infants born to mothers with HBV, healthcare workers, and people in high-prevalence regions.

Global Impact: Efforts to expand hepatitis B immunization to all corners of the world have the potential to knowingly reduce the global burden of hepatitis B.

Global Vaccination Efforts

Efforts to expand hepatitis B immunization on a global scale have been extensive. The World Health Organization (WHO) recommends integrating hepatitis B vaccination into routine childhood immunization programs. The Global Vaccine Action Plan (GVAP) sets ambitious targets to reduce hepatitis B incidence and mortality. Initiatives like the GAVI Alliance have played a vital role in making vaccines accessible to low-income countries.

Challenges and Future Directions

While hepatitis B immunization has been highly successful, several challenges remain:

Vaccine Coverage: Achieving and maintaining high vaccine coverage rates, especially in underserved communities, remains a challenge.

Birth Dose Vaccination: Administering the first quantity of hepatitis B vaccine within 24 hours of birth is crucial to preventing mother-to-child transmission, but coverage in this critical window varies.

Affordability and Accessibility: Ensuring that vaccines are affordable and accessible to all, especially in low- and middle-income countries, is essential.

Combating Vaccine Hesitancy: Like other vaccines, hepatitis