Hepatitis A Vaccine Protects Kids and Adults Around Them
Dr. Pia Fenimore
Dr. Joan Thode
In this installment in our series about diseases preventable by vaccination, we examine hepatitis A and why protection from vaccination is important. We will start, as usual, with an anatomy lesson.
What is hepatitis A?
One of our prior columns discussed hepatitis B. Hepatitis A is a separate virus from a very different family of viruses. While the two viruses share the fact that they infect and inflame (“-itis”) the cells of the liver (“hepa-”), their different viral characteristics cause very different disease courses.
Hepatitis A virus is spread by what’s known as the “fecal-oral route,” meaning that humans shed the virus via stool, which then contaminates food, water or surfaces. Another person can then unknowingly ingest the virus.
Hepatitis A causes a disruption of the processing of a cell protein called bilirubin. When bilirubin builds up in the bloodstream, circulating around while waiting to be processed by the liver, it causes jaundice as well as intense itching. Meanwhile, the stagnation of bile (known as cholestasis) causes liver pain, nausea, vomiting and fever. In addition, the kidneys must filter out more bilirubin from the bloodstream; this causes the urine to become very dark, while the lack of bile in the intestines causes stools to appear white or gray.
Hepatitis A causes a more acute disease because it is a single-strand RNA (mRNA, or messenger RNA) that does not involve the cell nucleus. Instead, it uses the hepatocyte’s cellular machinery to make hundreds of copies of itself. These copies spread quickly from cell to cell, and typically within three weeks of ingesting hepatitis A viral particles, the liver becomes widely infected.
The liver clears some of these viral copies via the bile, and despite the cholestasis, whatever bile does make it into the intestine holds thousands of hepatitis A viral particles. These particles remain alive, integrate into the stool, and eventually leave the body, potentially infecting others.
The immune system mounts an attack response against the liver cells infected by the virus, causing damage and additional abdominal pain and inhibited hepatocyte function. As this acute inflammatory phase is comparatively shorter than that waged against hepatitis B, the liver can typically recover fully after hepatitis A infection. While this might make one question the need for a vaccine for a relatively self-limited virus, the vaccine prevents the intense suffering caused by acute infection and, equally importantly, ensures avoidance of the rare but often fatal complication of acute liver failure. Acute liver failure from hepatitis A virus can carry up to a 40% mortality rate and often requires a liver transplant.
Risks of hepatitis A infection
In the past, a hep A infection was associated with foreign travel. In fact, the vaccine remains a requirement for travel to many countries. However, in the United States, the infection is associated with child care centers and elderly care homes. Good hand hygiene has been shown to make a difference in preventing outbreaks. There are still annual outbreaks associated with contaminated food or water supply; however, most cases have been through contact with an infected person.
According to the American Liver Foundation, more than 180,000 children and adults are infected with this virus each year, “making it the sixth most commonly reported infectious disease in the United States.”
Hepatitis A is a reportable illness so the Pennsylvania Department of Health is often involved in contact tracing and may identify specific exposures at day care centers, restaurants, grocery stores, etc.
Because there is no way to identify who may be exposed in the future, universal vaccination is recommended.
What are hepatitis A symptoms?
In children, symptoms of hepatitis A are typically very mild — this is one of the reasons to support vaccination.
Confused? Stay with us here.
According to the Centers for Disease Control and Prevention, 70% of infected children from infancy to age 6 years are asymptomatic. Symptoms from hepatitis A infection typically develop about 15 to 50 days after exposure. Fever, vomiting and diarrhea are the most common symptoms of hepatitis A, followed by jaundice after about one week of symptoms. Liver enzyme elevation and swelling of the liver can occur after about one week of symptoms and can last two to six months. Acute liver failure occurs in about 0.3% of pediatric patients.
If most of the time symptoms in children are mild, then why do we worry about this virus? Outbreaks of hepatitis A do not usually become obvious until they have spread to an adult. Children shed the virus in the stool for months after infection, so they can infect adults very easily even when they are not sick. Babies and toddlers tend to shed viral particles in their stool for a longer period, making day care centers an understandably common setting for hepatitis A outbreaks.
People over the age of 40 are at higher risk for serious complications and prolonged illness. When vaccination rates among children decrease, the threat to unprotected adults increases, raising the likelihood that more adults will become infected. About 10% of adults with hepatitis A infection will develop serious complications such as painful rash and joint pain, as well as liver or cardiac disease. Relapsing infection is also more common in adults. Moreover, hepatitis A infection in pregnant women can cause preterm labor and other pregnancy complications. So, this is a case in which vaccinating infants also protects adults.
Recommended vaccine schedule
The American Academy of Pediatrics recommends that the two-dose hepatitis A vaccine be completed between age 12 months to 23 months, with the doses given six months apart. The vaccine is safe to give with other immunizations.
The vaccine can be given as early as 6 months of age when risk factors indicate an earlier start.
This immunization is very well tolerated. The most common side effects are arm soreness, fever and rash.
Catch-up vaccination
If your child was not vaccinated against hepatitis A as a baby, catch-up vaccination is recommended.
This recommendation includes older children and teens, especially as the risk of complications increases with age. Further, older kids often participate in mission trips and volunteer activities, or they may travel abroad. These are all activities that can increase their risk of contracting hepatitis A.
Does the vaccine work?
Yes! The two-dose series has been shown to produce near 100% development of the antibodies needed to prevent infection for life. Since the introduction of hepatitis A vaccination in 1995, the rates of hepatitis A infection have dropped by 95% in the United States.
Pia Fenimore, M.D., is a pediatrician at Lancaster Pediatric Associates and vice chair of pediatrics at Penn Medicine Lancaster General Health. Dr. Joan Thode, M.D., is a pediatrician at Penn Medicine Lancaster General Health Roseville Pediatrics. Both are fellows of the American Academy of Pediatrics.
