1. Immunisation Department, Centre for Infections, Health Protection Agency, London, United Kingdom
2. Vaccine and Immunisation Research Group, Murdoch Children's Research Institute and School of Population Health, University of Melbourne, Victoria, Australia
3. Statistics, Modelling and Economics Department, Centre for Infections, Health Protection Agency, London, United Kingdom
4. Gloucester Vaccine Evaluation Unit, Health Protection Agency, Gloucester, United Kingdom
5. Immunoassay Laboratory, Centre for Emergency Preparedness and Response, Health Protection Agency, Salisbury, United Kingdom
6. Immunoassay Laboratory, Institute of Child Health, London, United Kingdom