Immunization against Haemophilus influenzae type b outside the routine vaccination schedule

The epidemiology of the invasive disease caused by Haemophilus influenzae has changed drastically since the introduction of vaccines in the routine vaccination schedule. In high-income countries, Haemophilus influenzae infection has gone from being a disease predominantly occurring in children and due to serotype b, to being a disease more frequent in adults and caused mainly by non-typeable strains. Therefore, it is important to take into account adult vaccination risk factors such as hematopoietic stem cell transplantation, functional or surgical asplenia, or certain innate or acquired immune deficits. In addition to these established factors, this document reviews the aspects to be taken into account by the physician, such as the degree of functional hypoesplenia, the type of affectation of the complement pathway or the affectation of the immunity of the individual caused by monoclonal gammopathies.