Footnotes

• Ethical approval: The study protocol and consent forms were approved by the ethics review committees of Ste-Justine and Royal Victoria Hospitals (Montreal, Quebec, Canada). Informed consent was obtained from all patients or their parents or guardians.

• Competing interests: BJW has served on a number of Canadian and US government advisory committees addressing the issues of vaccine use and safety between 1994 and 2006. He has provided expert testimony for both the US and Quebec vaccine injury compensation programs. Dr Ward has also provided advice and teaching to Canadian government and industry groups in the area of vaccine immunology. He has conducted and participated in several studies of measles vaccine safety sponsored by Canadian and US government funding agencies. He has also conducted a small number of phase I and phase II industry-sponsored clinical trials of non-licensed vaccines for smaller biotechnology companies. He has conducted a single, company-sponsored, immunological study of a licensed, acellular pertussis vaccine. None of the other authors have conflicts of interest to declare.