Pertussis risk factors

Overview
Children who are too young to be fully vaccinated and those who have not completed the primary vaccination series are at highest risk for severe illness. Like measles, pertussis is highly contagious with up to 90% of susceptible household contacts developing clinical disease following exposure to an index case. Adolescents and adults become susceptible when immunity wanes. Adults and adolescents are the primary reservoir for pertussis. Pertussis is spread by contact with airborne discharges from the mucous membranes of infected people, who are most contagious during the catarrhal stage. Because the symptoms during the catarrhal stage are nonspecific, pertussis is usually not diagnosed until the appearance of the characteristic cough of the paroxysmal stage.