Haemophilus influenzae type B, or Hib, is a bacteria that can cause infections. It usually occurs in children under five years old. Hib can lead to:

People can carry Hib bacteria and not know it. These germs can spread from person to person. They usually spread through droplets from an infected person. Sickness will probably not occur when the germs stay in the nose and throat. They can cause serious problems when they spread into the lungs or the bloodstream.

Before the vaccine, severe Hib disease affected about 20,000 United States children under age five.

Symptoms include:

  • Fever
  • Drowsiness
  • Vomiting
  • Stiff neck
  • Other symptoms, depending on the part of the body affected

The Hib vaccine is made from inactive parts of the bacteria. It is injected into the muscle.