A Virologist Explains The Importance Of Preventing Hepatitis B

The recent discussions led by the CDC’s Advisory Committee on Immunization Practices (ACIP) regarding the potential delay of the hepatitis B vaccine for newborns have sparked renewed interest in this significant health issue. While the ACIP ultimately decided to table the proposed delay, this discourse highlights the critical need to understand hepatitis B and the crucial role of early vaccination in safeguarding public health.

Epidemiology and Transmission

According to the World Health Organization, over 250 million people were living with chronic hepatitis B as of 2022, leading to nearly 1 million deaths that year. Before the introduction of the hepatitis B vaccine, infections were significantly more common; in the 1980s, it is estimated that 200,000 to 300,000 Americans were infected annually, particularly among young adults, with healthcare workers facing infection rates of 1-2% per year on the job. Following the implementation of routine infant vaccination in 1991 and catch-up vaccination programs for older children and at-risk adults, annual infections have dramatically decreased to fewer than 20,000 cases, marking one of the most successful public health initiatives in modern history.

The hepatitis B virus (HBV) is estimated to be 100 times more infectious than HIV and spreads through contact with infected blood and bodily fluids. Perinatal transmission poses a significant risk, as infants can acquire the virus during childbirth from infected mothers; without preventive measures, up to 90% of infants born to mothers with active hepatitis B will contract the virus.

In the United States, adult infections primarily occur through sexual contact with an infected partner. Injection drug use involving shared needles or equipment also significantly increases transmission risk. Other less common but noteworthy routes include exposure to contaminated medical instruments and sharing personal items such as razors or toothbrushes with an infected person. Importantly, hepatitis B is not transmitted through casual contact, food sharing, or respiratory droplets.

Clinical Manifestations and Disease Progression

The presentation of hepatitis B infection varies depending on the age at infection and the individual’s immune response. Acute infections can lead to symptoms such as fatigue, nausea, abdominal pain, loss of appetite, and jaundice (the yellowing of skin and eyes). However, many individuals, especially infants and young children, may not exhibit noticeable symptoms at first.

The primary concern arises from chronic infection, which occurs in up to 90% of infected infants, 30% of children under five, and 5% of adults. Chronic hepatitis B can progressively damage the liver over decades, potentially resulting in cirrhosis, liver failure, and hepatocellular carcinoma (liver cancer). Moreover, chronic carriers, even in the absence of symptoms, can remain infectious throughout their lives, with a 15-25% lifetime risk of succumbing to liver disease—emphasizing the necessity of prevention through vaccination.

The Impact of Hepatitis B Vaccination

The hepatitis B vaccine is regarded as one of the major triumphs of modern medicine in public health. Since the initiation of routine infant vaccination in the United States in 1991, the incidence of new infections among children and adolescents has plummeted by over 95%.

Global data corroborate these striking outcomes; countries that have adopted universal infant vaccination have witnessed drops in chronic infection rates in children from 10-15% to below 1%. For instance, after implementing universal vaccination in 1984, Taiwan identified a 75% decrease in liver cancer rates among vaccinated populations.

The effectiveness of the vaccine extends beyond individual protection. By thwarting chronic infections, vaccination disrupts the cycle of transmission and brings about community-wide health benefits.

Why Early Prevention is Critical

The timing of hepatitis B vaccination is crucial, as the age at infection is inversely related to the likelihood of developing chronic infection. Adults have only a 5% chance of developing chronic infection; however, this risk escalates to 30% in children under five and nearly 90% in newborns.

Administering the vaccine at birth offers multiple advantages. It provides immediate protection against perinatal transmission, serves as a safety measure for infants whose mothers’ hepatitis B status may be unknown or inaccurately documented, and safeguards against early childhood exposure from infected household members.

Studies from countries that have delayed vaccination have observed increased rates of perinatal transmission and resulting chronic infections. Gaps in early protection can have enduring consequences, as chronic hepatitis B remains largely unmanageable despite available treatments.

Decades of safety data affirm that hepatitis B vaccines boast an excellent safety profile, with serious side effects occurring in fewer than one in a million doses. The most frequently encountered adverse effects include mild soreness at the injection site and low-grade fever, both of which resolve quickly. The benefits of preventing a potentially life-threatening chronic infection far outweigh the minimal risks associated with vaccination.

The hepatitis B vaccination epitomizes one of public health’s significant successes. The reduction of infection rates early in life profoundly impacts chronic infection rates, liver disease incidence, and mortality.