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Hepatitis A and B Vaccines

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What Is Hepatitis B and How Does It Differ From Hepatitis A?

Hepatitis B is caused by the hepatitis B virus or HBV. Like hepatitis A, it may start as an acute disease, causing a mild illness that lasts for a few weeks. But in some people, especially infants, the hepatitis B virus lingers, causing a lifelong chronic illness that causes long-term liver problems. Even people who have had the disease for 20 or 30 years without symptoms are at risk for serious liver problems, such as cirrhosis or liver cancer.

Hepatitis B is spread when blood, semen, or other bodily fluid of someone who has it enters the body of someone who doesn't. An infected mother can pass the disease on to her child at birth. You can also get the disease by:

  • Having unprotected sex with an infected partner
  • Sharing needles, syringes, or other drug paraphernalia
  • Using something that may contain an infected person's blood, such as a razor or toothbrush
  • Coming in direct contact with the blood of someone who has the disease
  • Being exposed to blood from needle sticks or other sharp instruments

Unlike hepatitis A, hepatitis B is not spread through food or water, and you can't get it from sharing eating utensils, hugging, kissing, holding hands, coughing, or sneezing. And if you are an infected mother, you can't pass it on to your child through breastfeeding.

Children younger than age 6 who have hepatitis B often have no symptoms. In older children and adults, symptoms of acute hepatitis B include:

  • Fever
  • Fatigue
  • Loss of appetite
  • Nausea
  • Vomiting
  • Abdominal pain
  • Dark urine
  • Clay-colored bowel movements
  • Joint pain
  • Jaundice

Close to 90% of infants who become infected with HBV will develop chronic hepatitis B and carry the disease with them for life.

How Effective Are the Vaccines for Hepatitis A and Hepatitis B, and Are They Safe?

Both the vaccines for hepatitis A and the vaccines for hepatitis B are highly effective. In studies of the four vaccines used for hepatitis A, nearly 100% of all adults who receive one develop protective levels of antibodies within one month of receiving a single dose. In addition, eight years after receiving two or more doses, 99% to 100% of vaccinated individuals were still fully protected. Results are similar for the hepatitis B vaccine, and experts estimate that both vaccines will give immunity for up to 20 or 30 years and possibly for life.

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