Although pertussis can be serious for adults, infants are the most vulnerable⁹

Pertussis is a highly contagious, infectious disease, which typically
progresses in 3 stages.

• The first stage of the infection is the catarrhal stage. Symptoms during this stage include runny nose, sneezing, and mild cough and may be easily mistaken for a common cold.⁹
• After 1 to 2 weeks, the infection may progress to the paroxysmal stage. This stage is characterized by bursts of rapid coughing attacks that are often accompanied by severe difficulty breathing. This can last up to 10 weeks.⁹
• During the convalescent stage, the cough becomes less severe and eventually disappears, though this may take weeks or months⁹

Pertussis may be associated with serious complications, including⁹

• Pneumonia
• Seizures
• Hospitalization
• Death

Although adults and adolescents may have serious complications, the disease is often milder or even asymptomatic in these age groups. Despite this fact, adults and adolescents may still transmit the disease to vulnerable infants.⁹