VCFCons: a versatile VCF-based consensus sequence generator for small genomes

Tseng, Elizabeth; Zeng, Qiandong; Iyer, Lax

We had developed VCFCons to address urgent need for a robust consensus sequence generator for SARS-CoV-2 viral surveillance, which presented several unique requirements, including: (a) low coverage areas should be noted with ‘N’s, (b) low frequency or suspicious variant calls need to be filtered. We have found that, while some existing tools such as bcftools can generate the desired consensus sequence, it required multiple filtering steps and additional scripting. VCFCons can generate consensus sequences based on variant calls in a VCF format with versatile filtering criteria based on coverage and estimated variant frequency. We applied VCFCons to the Labcorp SARS-CoV-2 sequencing data and showed that it generated correct consensus sequences that were successfully submitted to GISAID and NCBI. We hope the community will find value in this tool and aim to continue developing VCFCons to handle more complex viral data in the future.