The shift in demographic involvement and clinical characteristics of COVID-19 from wild-type to Delta variant: A bioinformatic analysis of SARS-CoV-2 genomic sequence metadata from the Indian population (Preprint)

BACKGROUND Delta variant (B.1.617.2) was considered the most dangerous SARS-CoV-2 strain; however, in-depth studies on its impact on demographic and clinical characteristics of COVID-19 are scarce. OBJECTIVE We aimed to investigate the shift in demographic and clinical characteristics of the COVID-19 pandemic with the emergence of the SARS-CoV-2 delta variant compared to the wild-type (WT) strain (B.1). METHODS A cross-sectional study of COVID-19 cases in the Indian population caused by wild-type (WT) strain (B.1) and delta variant SARS-CoV-2 was performed. The viral genomic sequence metadata containing demographic, vaccination, and patient status details [N =9500, NDelta=6238, NWT=3262] were statistically analyzed. RESULTS With delta variant, in comparison to WT strain, a higher proportion of young individuals (<20 years) were infected (0-9 years: 4.5% vs. 2.3%, 10-19 years: 9% vs. 7%). The proportion of women contracting infection was slightly higher (41% vs. 36%). Further, a higher proportion of the total young population (10% vs. 4%) and young (14% vs. 3%) as well as adult (20-59 years) (75% vs. 55%) women developed symptomatic illness and were hospitalized. 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. Odds of death increased irrespective of the sex (Odds ratio: 3.034, 95% Confidence Interval: 1.7-5.2, p<0.001), however, an increased proportion of women (32% vs. 25%) died. Frequent post-vaccination infections occurred following complete doses (24/6238). CONCLUSIONS The increased involvement of young individuals and women, the lower mean age for illness, higher mortality, and frequent post-vaccination infections were the significant epidemiological concerns with the delta variant.