The study will be conducted as a collaboration between the Health Protection Agency and the following study recruitment sites: Oxford Vaccine Group (OVG), Bristol Children's Vaccine Centre (BCVC), the Royal Devon and Exeter Hospital, St George's Vaccine Institute (SGVI) and the University of Southampton Wellcome Trust Clinical Research Facility (USWTCRF). Families in the area of these research sites will be notified of the study by methods including print and electronic media, posters and direct mail out via the child health computer departments. The study visits themselves will be conducted in locations such as hospital outpatients, GP surgeries, or schools. General practitioners will be informed of the study and all immunisations administered during the study, as will the relevant child health computer department.