Clinical characterization and Genomic analysis of COVID-19 breakthrough infections during second wave in different states of India (preprint)

ABSTRACT

During March to June 2021 India has experienced a deadly second wave of COVID19 with an increased number of post vaccination breakthrough infections reported across the country. To understand the possible reason of these breakthroughs we collected 677 clinical samples (throat swab/ nasal swabs) of individuals who had received two doses (n=592) and one dose (n=85) of vaccines (Covishield and Covaxin,) and tested positive for COVID19, from 17 states/Union Territories of country. These cases were telephonically interviewed and clinical data was analyzed. A total of 511 SARS-CoV-2 genomes were recovered with genome coverage of higher than 98% from both the cases. Analysis of both the cases determined that 86.69% (n=443) of them belonged to the Delta variant along with Alpha, Kappa, Delta AY.1 and Delta AY.2. The Delta variant clustered into 4 distinct sub-lineages. Sub-lineage I had mutations ORF1ab, A1306S, P2046L, P2287S, V2930L, T3255I, T3446A, G5063S, P5401L, A6319V and N G215C; Sub lineage II ORF1ab P309, A3209V, V3718A, G5063S, P5401L and ORF7a L116F; Sub lineage III ORF1ab A3209V, V3718A, T3750I, G5063S, P5401L and Spike A222V; Sub-lineage IV ORF1ab P309L, D2980N, F3138S and spike K77T. This study indicated that majority of the clinical cases in the breakthrough were infected with the Delta variant and only 9.8% cases required hospitalization while fatality was observed in only 0.4% cases. This clearly suggests that the vaccination does provide reduction in hospital admission and mortality.