In this study we wish to collect the full vaccination history of participants, as this information will be extremely important in interpreting results. We propose sending a letter to parents/guardians informing them of the study and asking whether they are willing for members of the study team to approach their general practitioner or the child health computer system in order to retrieve these records. Immunisation histories will then be included with other non-identifiable information needed for analysis, and samples unlinked from personal identifiers prior to analysis.