Nearly 40% of school age children in the United Kingdom who visit their family doctor with a persistent cough have evidence of whooping cough infection, even though they have been fully immunised, finds a study published on bmj.com today.

These startling results suggest that whooping cough is endemic among young children in the UK, with important implications for clinical practice and immunisation policy, say the authors.

Previous research in several countries has shown that Bordetella pertussis (whooping cough) infection is an endemic disease among adolescents and adults. Data also shows that neither infection nor immunisation results in lifelong immunity. Yet general practitioners in the UK seldom diagnose or even consider pertussis in older children. It is perceived as a disease of very young children who have not been immunised and who have classic features such as whoop.

So researchers set out to estimate the proportion of school age children in Oxfordshire with a persistent cough who have evidence of a recent pertussis infection.

They identified 172 children aged 5-16 years who visited their family doctor with a cough lasting 14 days or more. Details on the duration and severity of cough were recorded and immunisation records were checked. Blood samples were taken to test for pertussis infection and parents and children also completed a cough diary.

A total of 64 (37.2%) children had evidence of a recent pertussis infection; 55 (85.9%) of these children had been fully immunised.

Children with pertussis were more likely than others to have whooping, vomiting, and sputum production. They were also more likely to still be coughing two months after the start of their illness, continue to have more than five coughing episodes per day, and cause sleep disturbance for their parents.

These results show that a substantial proportion of immunised school age children presenting to UK primary care with a persistent cough have evidence of a recent infection with Bordetella pertussis, say the authors.

They urge general practitioners to be alert to a potential diagnosis of pertussis in any child who presents with a persistent cough. A clear diagnosis will allow general practitioners to give parents an indication of the likely length of cough and prevent them prescribing unnecessary drugs for asthma or referring children for further investigations, they conclude.

British Medical Journal