Hib vaccine in a vial, with a syringe. This vaccine protects against infection by the Hib bacterium Haemophilus influenzae type B that can cause a range of serious illnesses in children, including meningitis and a form of pneumonia. The vaccine is given in several courses in the first year of a baby's life. This is the Act-Hib brand of the Hib vaccine, and it is a conjugate vaccine that also contains diptheria and tetanus elements. A vaccine stimulates the body's immune system to produce antibodies, but without causing infection. The immune system can then respond quickly against future infections by the bacterium.