Why is the hepatitis a vaccine recommended before traveling?

Disease likely. Hepatits A is more common in many parts of the globe. When traveling you will want to check with your doctor about hepatitis A vaccination. If possible, plan for vaccination 4-6 weeks prior to departure. Hepatitis A is spread by poor hand washing, food and water. Adults suffer more than children from the illness. Hepatitis A is now a routine vaccine in childhood in the USA.
More common there. Hepatitis a is more common in developing countries and third world countries than here in the United States. The virus is in human sewage, so places where there is not a good sewage system will have hepatitis a problems.