The vaccine for hepatitis B has been shown to be very safe when given to infants, children or adults, according to the U.S. Centers for Disease Control and Prevention (CDC), which monitors vaccine safety. More than 100 million people have received the hepatitis B vaccine in the United States, and no serious side effects have been reported. The most common side effects from hepatitis B vaccination are pain at the injection site and, rarely, mild to moderate headache and fever. Studies show that these side effects are reported no more frequently among those vaccinated than among persons not receiving the vaccine.