The message for GPs is that whooping cough is still prevalent among school age children who see them with a persistent cough, even after the introduction of the preschool booster vaccination.
The purpose of the study was to look at the prevalence of whooping cough following the introduction of the preschool booster in 2001. Before that booster had been implemented, my colleagues in Oxford and the Health Protection Agency (now known as Public Health England) did a study which found that nearly two-fifths of school-age children presenting in primary care with persistent cough had evidence of recent whooping cough infection.
In our study, we looked at children between the ages of five and fifteen years who presented to their GP with a persistent cough which had been going on for between two and eight weeks. We recruited children from general practices located across the Thames Valley region.
The clinical case definition of whooping cough is a cough lasting two weeks or longer, plus at least one other classical feature (paroxysms of cough, post-tussive vomiting or whooping), in the absence of a more likely diagnosis.
However, we recruited children with persistent cough, with or without other classical features of whooping cough, because we know that infected individuals who have previously been vaccinated can get milder symptoms.
We included 279 children altogether, among whom vaccination coverage was over 90% for the primary vaccinations and around 80% for the preschool booster.
We found that of those 279, 56 had evidence of recent whooping cough infection – about 20% (one in five children). Whooping cough is therefore still prevalent among school age children who present in primary care with persistent cough.
We also looked at quarterly whooping cough detection rates in our study cohort and compared those to national whooping cough surveillance data. The variations over the period which we observed in our cohort were similar to those observed across the whole of England and Wales in the same age group. This gave us some confidence that our figures were generalisable.
Although our study demonstrates that whooping cough is still prevalent among school age children who see their GP with a persistent cough, we still need more evidence about the burden and the costs associated with whooping cough in this population. In the USA an adolescent booster was introduced in 2006. However, we still do not have sufficient evidence to say whether this has significantly reduced infant hospitalisations or deaths due to whooping cough. We therefore need to consider whether or not introducing an adolescent booster in the UK would be cost-effective.
Dr Kay Wang is academic clinical lecturer, Nuffield Department of Primary Care Health Sciences, University of Oxford