There are 4 current variants of concern (VOCs) and 10 variants under investigation (VUIs) (Table 1). This report has been published to continue to share the detailed variant surveillance analyses which contribute to the variant risk assessments and designation of new VOCs and VUIs. The specialist technical briefings contain early data and analysis on emerging variants and findings have a high level of uncertainty. A new risk assessment for VUI-21JUL-01 (B.1.621) has been published and is available here. There are no updates to the Delta (B.1.617.2) risk assessment this week. A separate report is published covering routine data on all other VOCs and VUIs. Principal changes and findings are: • there are no new VOCs or VUIs since the last briefing • the proportion of cases sequenced and genotyped remains relatively low but has started to recover as case numbers fall and capacity expands • Delta variant accounted for approximately 99% of sequenced and 98% genotyped cases from 25 July to 31 July 2021 • PCR cycle threshold (Ct) values from routinely undertaken tests in England show that Ct values (and by inference viral load) are similar between individuals who are unvaccinated and vaccinated. • the UK Genotype to Phenotype Consortium reports new data relating to VUI21JUL-01 (B.1.621). There is evidence of reduction in pseudovirus neutralisation by serum from individuals who have been vaccinated or previously infected with Delta All risk assessments are published separately on the PHE webpage, Investigation of SARS-CoV-2 variants of concern, except for Gamma, which was published within Technical Briefing 7 and Alpha within Technical Briefing 9. As Delta is the dominant variant in the UK, epidemiological data in the weekly surveillance report is also relevant