Hepatitis B

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 and are at risk of developing chronic hepatitis, cirrhosis or even liver cancer later in life. It is estimated that about 8% 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 6 weeks to 6 months. 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. Rarely, death may result from complications of the disease.

Most people with acute hepatitis B will develop antibodies against the virus and recover fully. About 6% of those infected become lifelong carriers.

Hepatitis B Carrier

An estimated 25% 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. About 70-90% 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.


The most effective way to prevent hepatitis B is through vaccination. Those people who do not possess either hepatitis B antigen or hepatitis B antibody in their bodies may consider receiving vaccination.

A hepatitis B 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 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.


A course of vaccination requires three doses of injection:

  • 1st dose: first month
  • 2nd dose: one month after the first dose
  • 3rd dose: five months after the first dose

For optimal production of antibodies against the disease, all three doses should be completed within 6 months.

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