Demographic characteristics of SARS-CoV-2 B.1.617.2 (Delta) variant infections in Indian population

Abstract

Importance: Higher risks of contracting infection, developing severe illness and mortality are known facts in aged and male sex if exposed to the wild type SARS-CoV-2 strains (Wuhan and B.1 strains). Now, accumulating evidence suggests greater involvement of lower age and narrowing the age and sex based differences for the severity of symptoms in infections with emerging SARS-CoV-2 variants. Delta variant (B.1.617.2) is now a globally dominant SARS-CoV-2 strain, however, current evidence on demographic characteristics for this variant are limited. Recently, delta variant caused a devastating second wave of COVID-19 in India. We performed a demographic characterization of COVID-19 cases in Indian population diagnosed with SARS-CoV-2 genomic sequencing for delta variant. Objective: To determine demographic characteristics of delta variant in terms of age and sex, severity of the illness and mortality rate, and post-vaccination infections. Design: A cross sectional study Setting: Demographic characteristics, including vaccination status (for two complete doses) and severity of the illness and mortality rate, of COVID-19 cases caused by wild type strain (B.1) and delta variant (B.1.617.2) of SARS-CoV-2 in Indian population were studied. Participants: COVID-19 cases for which SARS-CoV-2 genomic sequencing was performed and complete demographic details (age, sex, and location) were available, were included. Exposures: SARS-CoV-2 infection with Delta (B.1.617.2) variant and wild type (B.1) strain. Main Outcomes and Measures: The patient metadata containing details for demographic and vaccination status (two complete doses) of the COVID-19 patients with confirmed delta variant and WT (B.1) infections were analyzed [total number of cases (N) =9500, NDelta =6238, NWT=3262]. Further, severity of the illness and mortality were assessed in subsets of patients. Final data were tabulated and statistically analyzed to determine age and sex based differences in chances of getting infection and the severity of illness, and post-vaccination infections were compared between wild type and delta variant strains. Graphs were plotted to visualize the trends. Results: With delta variant, in comparison to wild type (B.1) strain, higher proportion of young age individuals (<20 year) (0-9 year: 4.47% vs. 2.3%, 10-19 year: 9% vs. 7%) were affected. The proportion of women contracting infection were increased (41% vs. 36%). The higher proportion of total young (0-19 year, 10% vs. 4%) (p=.017) population and young (14% vs. 3%) as well as adult (20-59 year, 75% vs. 55%) women developed symptoms/hospitalized with delta variant in comparison to B.1 infection (p< .00001). The mean age of contracting infection [Delta, men=37.9 (17.2) year, women=36.6 (17.6) year; B.1, men=39.6 (16.9) year and women= 40.1 (17.4) year (p<.001)] as well as developing symptoms/hospitalization [Delta, men=39.6(17.4) year, women=35.6(16.9) year; B.1, men=47(18) year and women= 49.5(20.9) year (p<.001)] was considerably lower. The total mortality was about 1.8 times higher (13% vs. 7%). Risk of death increased irrespective of the sex (Odds ratio: 3.034, 95% Confidence Interval: 1.7-5.2, p<0.001), however, increased proportion of women (32% vs. 25%) were demised. Further, multiple incidences of delta infections were noted following complete vaccination. Conclusions and Relevance: The increased involvement of young (0-19 year) and women, lower mean age for contracting infection and symptomatic illness/hospitalization, higher mortality, and frequent incidences of post-vaccination infections with delta variant compared to wild type strain raises significant epidemiological concerns.

Emerging SARS‐CoV‐2 variants can potentially break set epidemiological barriers in COVID‐19

“…An incremental increase in transmissibility of the emerging variants from B.1 to B.1.617.2 suggests that more numbers of younger age individuals, including pediatric age group, may get involved in the pandemic as the strains further evolve 1,2,4,35,79. Also, early indications for narrowing the sex-based differences in patient outcomes is an important epidemiological concern.83,84 In a recent study, among the Indian population, using data fromthe national clinical registry for COVID-19 authors have compared clinical profiles of the hospitalized patients during two successive COVID-19 waves (N = 12 059 and 6903). The authors noted that the mean age of the patients was significantly lower in the second wave (48.7 [18.1] year vs. 50.7 [18.0] year, p < 0.001) with more numbers of patients in the younger age groups intervals (<20, and 20-39 year).…”

“…The total mortality was about 1.8 times higher and the risk of death is increased irrespective of the sex (OR: 3.034, 95% CI: 1.7-5.2, p < 0.001). Interestingly, although, the proportion of mortality was still higher in men than women, an increased number of women (32% with Delta vs. 25% with B.1) died 84. F I G U R E 6 The global spread of emerging SARS-CoV-2 variants.…”

Biological Properties of SARS-CoV-2 Variants: Epidemiological Impact and Clinical Consequences

“…In India, the proportion of women who became infected with the Delta variant increased (41% vs. 36%), as did the risk of mortality (odds ratio: 3.034, 95% CI: 1.7-5.2, p < 0.001), with a higher proportion of women dying compared to men (32% vs. 25%) [405].…”

“…A study conducted by Hwang et al (2021) in South Korea showed that about half of affected people were under the age of 19 [404]. Kumar et al (2021) found that in comparison to the wild-type (B.1) strain, the Delta variant affected a higher proportion of younger age groups, particularly those younger than 20 years (0-9 years: 4.47% vs. 2.3%, 10-19 year: 9% vs. 7%) [405].…”

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“…When people arm themselves with vaccines, the SARS-CoV-2 virus mutates simultaneously. Alpha, Delta and Omicron variants rapidly took over their predecessors and became dominant, and they increased immune escape ability [14][15][16][17] and target cell affinity 40 , which, in turn, caused increased viral load 23 and symptomatic severity 41 , breaking through vaccine protection 42 and obtaining greater transmissibility 11 . We further incorporated the interactions between variants and the immune system into our computational framework and discussed how variants affect the individual-and population-level characters of primary infection and vaccine protection.…”