The classic clinical features of paroxysmal pertussis are often absent in older children and adults and after vaccination. The California pertussis epidemic of 2010 occurred in a highly vaccinated population.
All pediatric patients (0–18 years) with positive pertussis polymerase chain reaction from July to December 2010 were identified retrospectively from the Kaiser SCAL database. Information extracted by chart review included age at diagnosis, vaccine history, race, cough duration, number of clinic visits before diagnosis, presence of paroxysms, post-tussive emesis or wheezing, treatment for asthma during the course of illness and exposure to confirmed or suspected pertussis cases.
Overall 501 pediatric patients (mean age = 8.4 years) with positive pertussis nasopharyngeal polymerase chain reaction were identified. Complete DTaP series and Tdap vaccine had been received by 93% and 38% of eligible patients, respectively. Paroxysms, post-tussive emesis and wheezing on physical examination were present in 34%, 30% and 8% of patients, respectively. Each was associated with a longer duration of symptoms at diagnosis. Wheezing was associated with a delay in diagnosis (60% requiring >1 clinic visit for diagnosis vs. 29% in the overall population, P < 0.0001). Documented exposures were associated with a more timely pertussis diagnosis (after 9.4 days vs. 14.5 days; P < 0.0001).
Wheezing is present on examination of some patients with pertussis in a highly vaccinated pediatric population and appears to delay the diagnosis of pertussis. The presence of wheezing should not be used to exclude this diagnosis in children with chronic cough or other reasons to suspect pertussis.