Haemophilus influenzae is a type of germ (bacteria) that frequently lives in the back of the nose and throat. This is a state called carriage, and it is usually harmless but sometimes the bacteria can cause serious diseases such as meningitis or pneumonia. H. influenzae are transmitted through coughing and sneezing. There are six types of H. influenzae(a-f), of which type b (Hib) has historically caused the majority of illness among children. The Hib vaccine was introduced into the infant immunization schedule in 1991 and led to a dramatic reduction in the rate of Hib disease among children. In spite of its use, sporadic Hib disease continues to occur among Native American children. In addition, non-b types of H. influenzae, specifically type a (Hia), are also important causes of disease. Hia has become the leading cause of bacterial meningitis among Native American children. From 2004-2016, the annual rate of Hia disease among Navajo and White Mountain Apache children <5 years was nearly 20 times higher than the rate of all non-type b disease combined among general US children.
This study measured H. influenzae carriage and levels of immunity to Hib across childhood. The work guided strategies to prevent H. influenzae disease among Native communities in the southwest US.
In January 2019, we began enrolling Navajo and White Mountain Apache children into the carriage and immunity study. At the end of the study’s enrollment period, approximately 800 children 6 months through 14 years of age were enrolled.