Rate of recurrent collapse after vaccination with whole cell pertussis vaccine: follow up study.

We thank all families who kindly participated in the study. We are grateful to the Housing Department of the Birmingham City Council, Mrs Daphne Agnew, the staff of the seven hostels, the head teachers of the schools involved in the selection of the comparison sample, and Mr Saeed Haque for the statistical advice. Contributors: PV participated in the formulation of the study hypothesis, research design, data analysis and writing of the paper and is the guarantor of the paper. EG completed data collection and participated in data analysis and writing of the paper. SC participated in the formulation of the study hypothesis, research design, data analysis, and writing of the paper. Funding: Nuffield Foundation. Conflict of interest: None.