HealthDay News — One-fifth of school-aged children with persistent cough who participated in a recent study had evidence of pertussis, even among those who were fully vaccinated.

“[Pertussis] is one of the most common vaccine preventable diseases, causing nearly 300,000 deaths a year in children worldwide,” Kay Wang, BM, BCh, of University of Oxford in the United Kingdom, and colleagues reported in BMJ.

They estimated the prevalence and clinical severity of pertussis in 279 patients (aged 5 to 15 years) who presented with persistent cough at several general practices in the United Kingdom. They examined evidence of recent pertussis infection based on an oral fluid anti-pertussis toxin IgG titre of at least 70 arbitrary units. Cough frequency was assessed in six children diagnosed with laboratory-confirmed pertussis.

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Among the patients, 20% had evidence of recent pertussis infection, including 18% of the 215 fully vaccinated patients. Those who had received the preschool pertussis booster vaccination seven or more years previously had a more than three-found higher risk of pertussis compared with patients who had received it less than seven years earlier (40% versus 12%, respectively).

Children who received five and three component preschool pertussis booster vaccines had a similar risk of pertussis (risk ratio for five component vaccine, 1.14; 95% CI: 0.64-2.03). Cough frequency was more than 400 coughs in 24 hours in four of the six children for whom frequency was measured.

“Pertussis is still prevalent among school age children who present with persistent cough in primary care and can still manifest as clinically significant cough in fully vaccinated children,” wrote the researchers.