Hepatitis A Overview

Hepatitis A is a liver disease that results from infection with the Hepatitis A virus. It can range in severity from a mild illness lasting a few weeks to a severe illness lasting several months. Hepatitis A is usually spread when a person ingests fecal matter — even in microscopic amounts — from contact with objects, food, or drinks contaminated by the feces or stool of an infected person. Worldwide, there are an estimated 1.4 million hepatitis A infections annually. The vast majority of hepatitis A patients make a full recovery, and while the mortality rate is low, about 15% of patients do suffer from prolonged jaundice that can lead to other complications including liver failure that may require a transplant or lead to death.

Regions where hepatitis A is highly endemic include the Indian sub-continent (particularly Bangladesh, India, Nepal and Pakistan), Sub-Saharan and North Africa, parts of Asia, South and Central America and the Middle East. While the risk of acquiring hepatitis A in developed countries is low, non-immune travelers are at risk of contracting the disease during visits to countries of high or intermediate endemicity. Hepatitis A is one of the most common travel-related vaccine preventable diseases.

Symptoms most often show up 2 to 6 weeks after being exposed to the hepatitis A virus. Hepatitis A infection has four clinical phases*, although these do not occur in all patients. The first stage is an incubation period of 15 to 50 days. During this stage the infected person is asymptomatic but may be actively shedding the virus in the stool. The second stage is a period of several days to weeks that may precede the onset of jaundice. This period is characterized by nonspecific symptoms followed by gastrointestinal symptoms such as anorexia (loss of appetite), nausea, vomiting, abdominal pain, fatigue, malaise, and fever. Other symptoms at this stage may include myalgia (muscle pain), arthralgia (joint pain), cough, pharyngitis, constipation, diarrhea, pruritus (itchiness), and urticaria (hives). Dark urine caused by elevated bilirubin levels usually occurs prior the onset of jaundice. In the third stage, the characteristic yellowing of the skin and eyes of jaundice appear and most symptoms subside, although clinical signs such as hepatomegaly and hepatic tenderness are found in about half of patients. There is no treatment for HAV infection. Jaundice usually resolves within a few weeks. The final stage is a convalescent period during which the patient recovers.

Our Vaccine Candidate

PaxVax is in the process of re-developing a hepatitis A vaccine that was previously licensed as Epaxal in more than 40 countries. It is an aluminum-free hepatitis A vaccine and is the first hepatitis A vaccine to be based on virosome technology. The most common adverse reactions for the previously licensed vaccine are fatigue, injection site pain and headache.

 

References:

*WHO. The Global Prevalence of Hepatitis A. 2010. http://whqlibdoc.who.int/hq/2010/WHO_IVB_10.01_eng.pdf