Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). This virus can lead to both short-term, or acute, illness and a long-term, chronic condition. Immunity against Hepatitis B means the body has developed protection, making it resistant to the virus. If a person is not immune to Hepatitis B, they are susceptible, lacking the necessary defenses to fight off the infection if exposed.
Understanding Susceptibility to Hepatitis B
Susceptibility to Hepatitis B means an individual’s body does not possess the specific antibodies required to combat the virus. These protective antibodies, known as Hepatitis B surface antibodies (HBsAb or anti-HBs), are crucial for neutralizing the virus and preventing infection. A person’s susceptibility is determined through a simple blood test called Hepatitis B serology, which measures the level of HBsAb.
A negative HBsAb test result, or a level below 10 mIU/mL, signifies a lack of immunity, rendering the individual vulnerable to infection if exposed to HBV. Conversely, an HBsAb level greater than or equal to 10 mIU/mL indicates protection against the virus. This protective status can be acquired either through successful vaccination or from recovery after a natural infection.
How Hepatitis B is Transmitted
The Hepatitis B virus spreads when blood or other bodily fluids from an infected person enter the body of someone who is not immune. Transmission routes include direct blood-to-blood contact, such as sharing needles or syringes, or through unsterile medical procedures. Sexual contact is another way the virus can be transmitted. Additionally, the virus can pass from an infected mother to her baby during childbirth.
Hepatitis B is not transmitted through casual contact, such as sharing food or water, hugging, kissing, coughing, or sneezing. The virus requires the exchange of infected bodily fluids to establish an infection.
Preventing Hepatitis B Infection
For individuals not immune to Hepatitis B, vaccination is the most effective method to achieve protection. The Hepatitis B vaccine works by training the body’s immune system to produce the protective antibodies needed to fight off the virus. This vaccine is administered as a series of injections, commonly a three-dose series over several months. Completing the full vaccine series is necessary to ensure long-term immunity.
Beyond vaccination, other preventive measures are important for those not yet protected. Practicing safe sex reduces the risk of transmission. Avoiding the sharing of needles, syringes, and other drug injection equipment is also important. Personal care items that might have blood on them, such as razors or toothbrushes, should not be shared.
What Happens After Infection
When a person who is not immune contracts Hepatitis B, the infection can manifest in two ways: acute or chronic. Acute infection is the initial, short-term illness, lasting less than six months. Symptoms, if they appear, can include fatigue, nausea, vomiting, abdominal pain, dark urine, and jaundice. Many adults with acute Hepatitis B clear the virus and recover fully, though some may not experience any symptoms.
In some individuals, particularly those infected at birth or in early childhood, the virus persists, leading to a chronic infection that lasts six months or longer. Chronic Hepatitis B can damage the liver over many years, potentially resulting in serious conditions like cirrhosis or liver cancer. The risk of developing chronic infection is higher for infants infected at birth, with up to 90% developing chronic Hepatitis B, compared to 5-10% for adults infected later in life.