Injection Site Reactions

• Both hepatitis vaccinations can cause soreness and redness at the injection site. The hepatitis A vaccine causes this side effect in about one of two adults and one of six children, while the hepatitis B vaccine causes it in about one in four people.
  
  

Headache

• About one in six adults and one in 25 children develop a headache after receiving the hepatitis A vaccine, according to the CDC.
  
  

Less-Common Effects

• Other less-common side effects from the hepatitis A vaccination include lack of appetite, nausea, fatigue or low-grade fever, according to the Immunization Action Coalition. About one person in 15 receiving the hepatitis B vaccine develops a temperature of 99.9 degrees Fahrenheit or higher.
  
  

Additional Effects

• According to the University of Maryland Medical Center, side effects from a combination hepatitis vaccine are very similar to those of the vaccines administered individually. Additional possible but uncommon side effects include diarrhea, nausea, vomiting, upper respiratory infection and flu-like symptoms.
  
  

Allergic Reaction

• Some people have an allergic reaction to the vaccines, which can occur within a few minutes to a few hours, according to the CDC. This reaction is very rare. Symptoms include rash or hives, problems with breathing, hoarseness, chest tightness, and swelling of the face or mouth.