Inequalities associated with emergence of Delta SARS-CoV-2 variant of concern (B.1.617.2) in England: awareness for future variants

Health inequalities associated with COVID-19 in England were investigated soon after the initial peak of infections¹ generating significant public and political discussion. The recent report from the Commission on Race and Ethnic Disparities² generated further discourse as has vaccine inequalities on both a domestic³ and global⁴ scale. Delta was first detected in India in December 2020,⁵ with the first UK cases identified in April 2021; the variant emerged over the following months to later become the dominant strain among all sequenced cases in England.

We analysed available data on ethnicity, age group, sex and deprivation based on the Index of Multiple Deprivation (IMD) for all cases of the delta variant of SARS-CoV-2 (B.1.617.2) with a specimen date between 1 April and 30 September 2021. The IMD is a geographical deprivation measure based on a range of factors including income, crime, employment and health within a lower super output area (LSOA) containing around 1500 people. LSOAs are ranked based on their IMD score from the most to least deprived. We have categorised these scores into quintiles, with Q1 = most deprived and Q5 = least deprived.

Fig. 1 shows our main findings across these four key demographics. An immediate disparity is seen in ethnicity and deprivation with significantly higher rates in Asian and other ethnic groups as delta emerged in England; over time, these rates fluctuated, but since June 2021, the rate amongst other ethnic groups consistently remained the highest. Since the first detection, delta rates were highest amongst the more deprived populations, with little difference between Q3 and Q5 but a marked gap between Q3 to Q2 and Q1, respectively, showing an increase in burden amongst the most deprived. The highest rates occurred amongst 10- to 29-year olds, with increasing rates in 10- to 19-year olds likely reflecting the lack of vaccination in this age group and the return of schools. There is little difference in rates between sex.

Fig. 1.

Rates of SARS-CoV-2 delta variant cases by ethnicity, age, sex and deprivation, England April - September 2021.

Although the highest rates were amongst the most deprived, the distribution of delta cases by IMD quintile groups is different to that observed overall. Overall cases of COVID-19 (regardless of variant) have a linear distribution in relation to deprivation, whereas proportion and rates of delta in Q3-5 are very similar with a step change to Q2 and again to Q1. There is however a smaller gap between the least and most deprived with 22.4% of delta cases in Q1 versus 18.7% in Q5, compared to 24% of all cases in Q1 versus 16.3% in Q5.

Furthermore, the observed distribution of delta cases by IMD was different across age groups; in cases aged <20 years, the distribution reversed over time. In June, 26.6% were in Q1 versus 19.3% in Q5, but by September, this had changed to 17.9% in Q1 versus 24.1% in Q5. In 20- to 29-year olds, 23.5% of cases were in the most deprived areas compared to 15.5% in the least deprived with this gap increasing over time. The distribution of cases aged 30–59 years and ≥ 60 years has changed from a linear distribution with a higher proportion in Q1 to being equally distributed across quintile groups.

In summary, emergence of the delta variant of SARS-CoV-2 demonstrated a disproportional effect on more deprived communities, younger populations and ethnic groups other than white, prior to becoming the dominant variant. These disparities were observed despite the vaccination programme shifting the age distribution of cases with a much greater difference in proportion between the most and least deprived young adults compared to overall delta infections. As more variants such as Omicron (B.1.1.529) emerge, detailed surveillance is needed to monitor inequalities during the initial emergence phase and focus public health strategies.