10. Hib (Haemophilus Influenzae Type B) What it is: A bacterial disease that infects the lungs (pneumonia), brain or spinal cord (meningitis), blood, bone, or joints. How you get it: Some people have Hib bacteria in their nose or throat but are not ill. When they cough or sneeze, the bacteria go airborne. Babies and young children are especially at risk because their immune systems are weak. Why it’s serious: Before the Hib vaccine, about 20,000 U.S. children younger than 5 got Hib each year. About 3% to 6% of them died.