It’s always a good day to celebrate vaccines. As one of the all-time great achievements in medicine, vaccines are the reason humanity has been able to eradicate smallpox, end the “summer plagues” of polio, and slash the incidence of cervical cancer, to name just a few. But there’s one disease that gets a bit less publicity, despite it being a significant cause of serious childhood infections before a vaccine was introduced in the 1980s: Hib.

Hib disease is caused by a bacterium called Haemophilus influenzae type B. First described in 1892 by Richard Pfeiffer, it was thought at the time to be the cause of influenza, as the bacteria were found in sputum samples from influenza patients. It was a good thought, but now we know that the flu is caused by a virus. 

H. influenzae was later understood to be a secondary infection in these patients. In fact, the bacterium can sometimes sit harmlessly inside the nose. But when it does cause disease, it can quickly get very serious. 

Hib used to be the most common cause of bacterial meningitis in children, with symptoms including fever, headache, stiff neck, and vomiting. In more severe cases, this could progress to seizures and coma. Case fatality rates vary depending on access to prompt medical care and antibiotics, but can be as high as 40 percent, according to the European Centre for Disease Prevention and Control (ECDC). 

Even with recovery, meningitis carries the risk of lifelong complications, including vision and hearing loss. Other presentations of Hib disease include epiglottitis, a potentially deadly swelling of the throat, cellulitis, pneumonia, and septicemia.