variants under investigation 35 Figure 12. Incidents managed by Health Protection Teams involving SARS-CoV-2 variants (excluding Delta) by iso-week, by outbreak setting (4 January 2021 up to 20 June 2021). (Find accessible and auxiliary data used in this graph in underlying data). SARS-CoV-2 variants of concern and variants under investigation 36 Common exposures derived from contact tracing data Figure 13 shows the number of common exposure events reported per week, by setting, from week commencing 28 April to week of 2 June 2021. This figure only includes common exposures reported during contact tracing by cases who have been sequenced and confirmed as Alpha or Delta variant. Common exposures are derived from contact tracing data and are defined as specific venues visited outside the home by at least 2 cases during their pre-symptomatic period (2 to 7 days before symptom onset), on the same day or up to 7 days apart. A single common exposure event represents a visit by a case on a particular day to the common exposure setting. Common exposure events may represent transmission events between known cases but also from unknown cases. However, they can also simply represent commonly visited locations and so should be interpreted with caution. Settings visited regularly (for example daily school or workplace attendance), can be enhanced in the data as each of the separate visits are counted. Fewer common exposures occur when settings are closed or limited due to restrictions, so should be interpreted in the context of national policy as well as other events such as school holiday periods. The most common settings for common exposures were education settings, for both Alpha and Delta variants, in the first 4 weeks presented in Figure 13. The most recent 2 weeks presented, beginning 26 May and 2 June, include the bank holiday weekend and school half term week. In these most recent 2 weeks, hospitality settings were a larger proportion (around 20%) of all common exposures reported by cases with both Alpha and Delta variants, and the proportion of common exposures related to travel also increased substantially. SARS-CoV-2 variants of concern and variants under investigation 37 Figure 13. Weekly number and proportion of common exposure events among sequenced cases, by setting and variant of cases (for Alpha and Delta only), Common exposure events reported from week commencing 28 April 2021 to week commencing 2 June 2021. Variant data as of 21 June 2021, contact tracing data as of 23 June 2021. Number of common exposures per week of data labelled. (Find accessible data used in this graph in underlying data). SARS-CoV-2 variants of concern and variants under investigation 38 Part 2: Delta (B.1.617.2) surveillance The lineage B.1.617.2 was escalated to a variant of concern in the UK on 6 May 2021 (VOC-21APR-02). This variant was named Delta by WHO on 31 May 2021. Severity Complementary analyses undertaken in England and Scotland found an increased risk of hospitalisation in cases who were S gene target positive (Scotland) or had sequenceconfirmed Delta variant infection (England). These analyses have been reported in technical briefings 15 and 16. Further analyses are required to reduce the uncertainty related to the change in risk and to explore the link to vaccination in more detail. England No new data in this report. Scotland In the Public Health Scotland/EAVE II study, Cox proportional hazard regression was used to estimate risk factors for the time from test to hospitalisation among individuals who tested positive. Hospitalisation with COVID-19 was defined as any admission within 14 days of a positive test or where there was a positive test within 2 days of admission. The model was adjusted for age and days from 1 April 2021 as spline terms together with number of co morbid conditions, gender and vaccination status. Vaccination status was determined at the data of the PCR test. Individuals who tested positive from 1 April 2021 onwards (until 21 June 2021) were included in this analysis. There was an increased hazard ratio of hospitalisation for those who were S-gene positive compared with those with S gene target failure (1.8, 95% 1.4 to 2.4). Monitoring of vaccine effectiveness Analysis of routine testing data up to the 11 June 2021, linked to sequencing and S-gene target status has been used to estimate vaccine effectiveness against symptomatic disease using a test negative case control design. Methods and detailed results are available in Effectiveness of COVID-19 vaccines against the Delta variant. After a single dose there was an 14% absolute reduction in vaccine effectiveness against symptomatic disease with Delta compared to Alpha, and a smaller 10% reduction in effectiveness after 2 doses (Table 8). SARS-CoV-2 variants of concern and variants under investigation 39 Table 8. Vaccine effectiveness against symptomatic disease for Alpha and Delta variants Vaccination status Vaccine effectiveness (%) Alpha Delta Dose 1 49 (46 to 52) 35 (32 to 38) Dose 2 89 (87 to 90) 79 (78 to 80) Vaccine effectiveness against hospitalisation was estimated by evaluating hospitalisation rates via emergency care among symptomatic confirmed cases using survival analysis (Stowe et al., 2021 pre-print). This analyses used available data from linkage of symptomatic cases, 12 April to the 11 June 2021