1. Public Health England. Variants: distribution of case data, 11 June 2021. 18 June2021. www.gov.uk/government/publications/covid-19-variants-genomically-confirmed-case-numbers/variants-distribution-of-case-data-18-june-2021.
2. Public Health England. Effectiveness of covid-19 vaccines against hospital admission with the Delta (B.1.617.2) variant. 14 June 2021. https://khub.net/web/phe-national/public-library/-/document_library/v2WsRK3ZlEig/view/479607266.
3. Public Health England. Investigation of SARS-CoV-2 variants of concern: technical briefings. 18 June 2021. www.gov.uk/government/publications/investigation-of-novel-sars-cov-2-variant-variant-of-concern-20201201.
4. Independent SAGE. The Independent Sage Report 44: Continuing need for support measures. 18 June 2021. www.independentsage.org/wp-content/uploads/2021/06/Supprt-document-final.pdf.