As these symptoms wane, the child begins to develop a dry, hacking cough, which builds in intensity over time. Post-cough vomiting is classic and very suggestive of the diagnosis. Between paroxysms of coughing, the children appear well. This is the paroxysmal phase. Gradually these symptoms abate in the convalescent phase.
Infants have the highest hospitalization and complication rates.
Fifty percent or more of infants who contract pertussis are hospitalised. Pertussis infection in the very small infant might also be implicated in some apparent SIDS cases. Broken ribs are very common in full-blown adult pertussis. Imagine coughing hard enough to break your ribs. Young children who get pertussis usually catch it from adults.