What is Hepatitis B?
Hepatitis B is caused by a virus which damages the liver cells and impairs liver function. After infection, some people become permanent carriers of the hepatitis B virus (HBV) and are at risk of developing chronic hepatitis, cirrhosis or even liver cancer later in life. It is estimated that about 5.6% of the Hong Kong population are carriers.
How is Hepatitis B transmitted?
The hepatitis B virus is present in blood and body fluids such as saliva, semen, vaginal secretion and other body secretions. Its main routes of transmission are:
- Sexual contact with an infected person
- Mother to baby transmission
- Blood exposure through blood transfusion, or by sharing contaminated needles, toothbrushes, shaving razors, etc.
Acute Hepatitis B
The incubation period ranges from 1 to 6 months with an average of 75 days. Symptoms include loss of appetite, chills and fever, nausea, vomiting, malaise, joint pain, jaundice, tea-coloured urine and liver enlargement, etc. Some patients present little or no symptoms especially for infants and young children. Rarely, death may result from complications of the disease.
Most people with acute hepatitis B will develop antibodies against the virus and recover fully. Some people fail to clear the virus and develop chronic hepatitis B (CHB). The younger a person is when infected with hepatitis B, the higher the risk of developing chronic infection. Up to 90% of newborn babies infected with HBV would develop CHB, while the risk for adults is about 5%.
Hepatitis B Carrier
About 15-40% of hepatitis B carriers will progress to chronic hepatitis, cirrhosis or liver cancer. These complications usually develop during the ages of 50 to 60. To facilitate early diagnosis and treatment, hepatitis B carriers should undergo regular tests to monitor the liver function and status.
Although carriers appear healthy, the virus remains dormant in their body and may be transmitted to others through blood and body fluids contact. Since the symptoms of infection are mild in most cases, carriers may be unaware that they carry the virus and may pass it to their spouse and children unknowingly.
How would Hepatitis B affect your offspring
If a pregnant woman is a hepatitis B carrier, she may transmit the virus to her baby. Up to 90% of infants infected by the virus become carriers. Couples planning to have children should therefore try to protect themselves and their next generation from hepatitis B.
Prevention
The most effective way to prevent hepatitis B is through vaccination. Those people who do not possess either hepatitis B surface antigen or hepatitis B surface antibody in their bodies may consider receiving vaccination.
A hepatitis B surface antigen test detects whether a person is infected with the hepatitis B virus. A positive result indicates that a person has been infected in the past and has become a lifelong carrier. This person does not need vaccination.
A hepatitis B surface antibody test screens for the presence of hepatitis B antibody. If present in a person who had not been vaccinated, it means that a person has recovered fully from an infection and developed lifelong immunity.
Vaccination
A course of vaccination requires three doses of injection:
- 1st dose
- 2nd dose: one month after the first dose
- 3rd dose: six months after the first dose
For optimal production of antibodies against the disease, all three doses should be completed within 6 months.
All newborn babies should receive the birth dose of hepatitis B vaccination within 24 hours of birth. Afterwards, they should receive the second and third dose of the vaccination at the age of one month and six months respectively. After completing the three-dose course of vaccination, 90-95% of babies can produce adequate protective antibody to protect them from HBV infection.
Reduction of Mother-to-Child transmission of Hepatitis B
Mothers with a lot of virus in the body can take antiviral drugs to lower the transmission to babies.
Babies born to mother with CHB should
- be given hepatitis B immunoglobulin within 24 hours after birth for immediate extra protection
- receive hepatitis B vaccination as usual
- be tested on hepatitis B surface antibody and hepatitis B surface antigen at the age of 9-12 months to see whether they are protected or not
