Surveillance genome sequencing reveals multiple SARS-CoV-2 variants circulating in central Texas, USA, with a predominance of delta variant and review of vaccine breakthrough cases.

As surges in the COVID-19 pandemic have continued worldwide, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has mutated, spawning several new variants, and impacting, to various degrees, transmission, disease severity, diagnostics, therapeutics, and natural and vaccine-induced immunity. Baylor Scott & White Health has implemented, along with laboratory diagnosis, SARS-CoV-2 sequencing to identify variants in its geographical service area. We analyzed virus sequencing results of specimens collected across Central Texas and found dramatic changes in variant distribution in the first half of 2021. The alpha variant (B 1.1.7) became predominant at week 13 and continued dominance until week 25. A growth rate of 1.20 (R  = 0.92) for the first 15 weeks was noted and this growth gradually declined to -0.55 (R  = 0.99) for the final 13 weeks. Currently, B.1.1.7 is being displaced with B.1.617.2 at a 0.58 growth rate (R  = 0.97). We also investigated vaccine breakthrough cases (VBCs) within our healthcare system and present clinical data on 28 symptomatic patients.