This study advises that a diagnosis of whooping cough still be considered for those fully immunised if they display appropriate symptoms and shows that vaccination does not prevent the disease. In the study below over 85% of children presenting with whooping cough had been fully vaccinated.

Anthony Harnden, university lecturer(1), Cameron Grant, associate professor of paediatrics(2), Timothy Harrison, deputy director(3), Rafael Perera, senior research fellow in statistics(1), Angela B Brueggemann, senior research fellow in molecular biology(1), Richard Mayon-White, epidemiologist(1), David Mant, professor of general practice(1). Whooping cough in school age children with persistent cough: prospective cohort study in primary care. BMJ 2006;333:174-177 (22 July).

(1) Department of Primary health Care, University of Oxford, Oxford OX3 7LF, (2) Department of Paediatrics, University of Auckland, Starship Children's Hospital, Auckland, New Zealand, (3) Respiratory and Systematic Infection Laboratory, health Protection Agency, Centre for infections, London

Objective To estimate the proportion of school age children with a persistent cough who have evidence of a recent Bordetella pertussis infection.

Design Prospective cohort study (October 2001 to March 2005).

Setting General practices in Oxfordshire, England.

Participants 172 children aged 5-16 years who presented to their general practitioner with a cough lasting 14 days or more who consented to have a blood test.

Main outcome measures Serological evidence of a recent Bordetella pertussis infection; symptoms at presentation; duration and severity of cough; sleep disturbance (parents and child).

Results 64 (37.2%, 95% confidence interval 30.0% to 44.4%) children had serological evidence of a recent Bordetella pertussis infection; 55 (85.9%) of these children had been fully immunised. At presentation, children with whooping cough were more likely than others to have whooping (odds ratio 2.85, 95% confidence interval 1.39 to 5.82), vomiting (4.35, 2.04 to 9.25), and sputum production (2.39, 1.14 to 5.02). Children with whooping cough were also more likely to still be coughing two months after the start of their illness (85% v 48%; P = 0.001), continue to have more than five coughing episodes a day (P = 0.049), and cause sleep disturbance for their parents (P = 0.003).

Conclusions For school age children presenting to primary care with a cough lasting two weeks or more, a diagnosis of whooping cough should be considered even if the child has been immunised. Making a secure diagnosis of whooping cough may prevent inappropriate investigations and treatment.