Data sources . Almost all residents in Scotland are registered with a general practice and have a unique Community Health Index ( CHI ) number used by NHS Scotland . We used the CHI number to deterministically link all datasets with vaccination records in Public Health Scotland ( Extended Data Fig . 4 ) . Vaccination information was extracted from the general practice records and the Turas Vaccination Management Tool system ; together , these captured all vaccination records , including those vaccinated in general practices , community vaccination hubs and other settings , such as care homes and hospitals in Scotland 40 . Further details on the data sources used in this study are available in a published project protocol 24 .