Pertussis (whooping cough) is caused by Bordetella pertussis, a small Gram-negative coccobacillus that infects the musosal layers of the human respiratory tract. It is transmitted from infected to susceptible individuals through respiratory droplets. After an incubation phase of 7-10 days patients develop nose and throat inflammation and cough, and in the course of 1-2 weeks coughing paroxysms ending in the classical 'whoop' may occur. Bronchopneumonia, causing relatively high mortality, is the most prominent problem associated with pertussis. Pertussis remains an important cause of infant death worldwide and continues to be a public health concern even in countries with high vaccination coverage. Maternal antibodies do not appear to protect neonates from severe pertussis, and even for individuals with vaccine-induced immunity, the initial antibody-mediated immune response to b. pertussis may minimize the toxic damage to both epithelial and immune cells, but it has limited impact on its subsequent circulation among non-immunized children and older individuals with waning immunity.
Following the introduction of pertussis vaccination during the 1950s - 1960s, a dramatic reduction (<90%) in pertussis incidence and mortality was observed in the industrialized world. Pertussis vaccine has thus been part of the WHO Expanded Program on Immunization since its inception in 1974.