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Hepatitis B: Everything You Need to Know

Written by Sophie Keshishian, Peer Reviewed by Emily Begnel, Edited by Courtney Coleman


As many as 1.89 million people are living with Hepatitis B in the US today, two-thirds of whom are unaware of their infection. This statistic may be surprising to those unfamiliar with how the hepatitis B virus (HBV) is transmitted and contracted (1). Hepatitis B, also known as serum hepatitis, is a liver infection that develops following infection with HBV. HBV is spread through the transfer of bodily fluids–including blood, semen, and vaginal fluids–from an infected to an uninfected person. This sharing of bodily fluids can occur through needles or syringes, sexual intercourse, and blood transfusions, or via vertical transmission from mother to child during pregnancy. Upon infection, symptoms in newly-infected people vary–some may be asymptomatic, while others may experience symptoms ranging from fatigue and nausea to jaundice. Similarly, the chronicity, or duration, of the illness also varies from person to person, chronic cases primarily being those who are infected at a young age. Because this virus often goes undetected, it is crucial to remain informed on its transmission and methods to get tested.

Transmission and Symptoms

There are many ways in which HBV can spread, many of which are infrequently recognized. HBV can be transmitted via puncturing of the skin, such as by an accidental needle stick. It also spreads through mucosal contact, in which infectious bodily fluid – blood, semen, vaginal fluids, and/or saliva – contacts the skin, mouth, eyes, or open wounds. The virus can also be vertically transmitted from a mother to an infant during pregnancy, or horizontally

transmitted as a result of contact with infectious body fluids during childbirth. Some actions that put you at greater risk of contracting HBV include having unprotected sex with an infected person, being in contact with blood, getting a tattoo or acupuncture with unsanitary needles, sharing needles during drug use, sharing personal hygiene items, being on long-term hemodialysis and, although less likely, receiving blood transfusions (2). Dialysis patients are susceptible due to increased contact with potentially contaminated medical equipment and contact with dialysis staff members. Also, keep in mind that blood transfusions are less likely to cause infection due to the extensive screening processes of donated blood conducted by blood banks to ensure the infection is not spread from donor to recipient.

The earliest signs of HBV infection include fatigue, appetite loss, low-grade fever, muscle and joint pain, nausea and vomiting, jaundice, and dark urine. Among those that are symptomatic, symptoms may arise rapidly (within 3-8 weeks); however, they may take up to 6 months to arise, and it is possible to be asymptomatic. These initial symptoms may persist for a few weeks or months as the immune system fights off the infection. It is possible

that the immune system is unable to destroy the virus, whether symptomatic or not, leading to chronic HBV. Patients with chronic HBV may eventually develop symptoms of liver damage and liver cirrhosis, or scarring. People who contract HBV in adulthood are more likely to recover from acute HBV, whereas 90% of infected infants and 25-50% of 1–5-year-old children develop chronic HBV (1). Because HBV can be severe, yet asymptomatic, any suspicion or concerns of infection must be examined by a doctor.

Fig 1. Interpreting Hepatitis B Blood Test Results (Hepatitis B Foundation) Source: “Hepatitis B Blood Tests.” Hepatitis B Foundation, 2022, Accessed 11 October 2022. * Inform all doctors about a prior or current hepatitis B infection and include this information as part of your health history. Talk to doctors before taking immune system-suppressing medications to understand the risk for possible hepatitis B reactivation.

Exams and Screening

Some may ask, “I think I may be at risk of having HBV. What now?” If you suspect you have been exposed to HBV, or are part of a high-risk group, it is important that you be screened. The CDC recommends that the following groups get screened: people born in countries with a prevalence of HBV, US-born citizens with parents born in HBV-prevalent regions, people with elevated alanine aminotransferase (liver enzyme) levels, men who have sex with men, people living with HIV, people who inject drugs, immunosuppressive therapy recipients, blood and tissue donors, and pregnant people (1). Testing for hepatitis B requires one blood sample, which is then run through a three-part Hepatitis B panel. The first part is a hepatitis B surface antigen (HBsAg) test, which determines whether you currently have HBV infection by looking for the presence of emitted viral pieces or proteins, called antigens. (3). The second part is a hepatitis B surface antibody (HBsAb) test, which determines one’s immunity to HBV by detecting antibodies, or proteins which bind to antigens and make it easier for the immune system to attack the virus (3). The final part is a hepatitis B core antibody (HBcAb) test, which indicates either past or current HBV infection by detecting antibodies which target the core part of the virus. It is necessary to consult a doctor to understand the meaning of this test result and how to proceed (3).

For a more digestible interpretation of frequently asked questions, various test results, and their meanings, see Figure 1 (3, 4).

Vaccination for Adults and Children

Vaccination is a great way to prevent severe cases of HBV infection. The United States Advisory Committee on Immunization Practices recommends that infants - adults 60 years of age with risk factors be vaccinated for HBV. It is also recommended that infants are vaccinated at birth as a safety precaution to prevent perinatal transmission in the case that the mother may unknowingly be carrying the infection. Additionally, it has been shown that vaccination at birth increases the likelihood that the child will complete their vaccination series on schedule, with the first series of vaccination being completed at 6-18 months of age (6). Adults over 60 who do not have risk factors may also be vaccinated if they choose (5, 6). In the US, there are three single-antigen vaccines, one three-antigen vaccine, and three combination vaccines licensed by the FDA: Engerix-B, Recombivax HB, Heplisav-B, PreHevbrio, Pediarix, Twinrix, and Vaxelis, respectively (6). Engerix-B and Recombivax HB are approved for vaccination at birth as well as for adults. Hepsilav-B and PreHevBrio are approved only for people 18 years of age or older. Studies show that those who received Hepatitis B vaccination later than 6 months of age retained immunological memory and protection for at least 30 years. Follow-up studies are still being conducted to elucidate the duration of immunity for those vaccinated at birth. Regardless, vaccination at birth serves as an important cautionary measure in case of unsuspecting transmission within the family.

Although the prevalence of Hepatitis B has declined since the rise in vaccinations, the possibility of contracting the potentially lethal infection still exists, especially for those traveling from the US to regions with higher prevalence. According to the CDC, the rate of reported HBV cases declined 90% since recommendations for vaccinations in the U.S. were initially issued, dropping from 9.6 cases per 100,000 population in 1982 to 1.0 cases per

100,000 in 2018 (7). Evidently, vaccination is an effective way to prevent transmission of HBV and keep populations healthy. To prevent infection and keep high-risk persons safe, it is important to conduct all necessary measures, from proper screening to vaccination, in order to prevent the spread of Hepatitis B.



1. “Hepatitis B Questions and Answers for Health Professionals.” Centers for Disease Control and Prevention, 30 March 2021, Accessed 2 October 2022.

2. “Hepatitis B.” Mount Sinai, 6 February 2022, Accessed 2 October 2022.

3. “Hepatitis B Blood Tests.” Hepatitis B Foundation, 2022, Accessed 11 October 2022.

4. Center for Substance Abuse Treatment. Addressing Viral Hepatitis in People With Substance Use Disorders. Rockville (MD): Substance Abuse and Mental Health Services Administration (US); 2011. (Treatment Improvement Protocol (TIP) Series, No. 53.) 2, Screening for Viral Hepatitis. Available from: Accessed 11 October 2022.

5. “Hepatitis B Vaccination of Adults.” Centers for Disease Control and Prevention, 28 March 2022, Accessed 12 October 2022.

6. “Hepatitis B Vaccination of Infants, Children, and Adolescents.” Centers for Disease Control and Prevention, 8 November 2019, Accessed 12 October 2022.

7. “Epidemiology and Prevention of Vaccine-Preventable Diseases: Hepatitis B.” Centers for Disease Control and Prevention, 18 August 2021, Accessed 13 November 2022.


This post is not a substitute for professional advice. If you believe that you may be experiencing a medical emergency, please contact your primary care physician, or go to the nearest Emergency Room. Results from ongoing research is constantly evolving. This post contains information that was last updated on November 26, 2022.


Sophie Keshishian is currently an intended Molecular and Cell Biology (Immunology) major undergraduate at UC Berkeley.

Emily Begnel is a second year PhD student in the University of Washington Department of Epidemiology.

Courtney Coleman is a master's degree candidate in biology at Harvard and Co-President of Students vs. Pandemics.

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