SARS-CoV2 Wild-type and Delta VOC infection dynamics in a Paediatric cohort in India (South)

Background: SARS CoV-2 infection virus dynamics, severity and immune response are different in children and adults. Limited reports of the differential impact of variants in children exist, and none have been reported from LMICs. Methods: We recruited a prospective cohort of SARS CoV-2 PCR positive children between November 2020 and May 2021 and compared virus characteristics (viral load, wild-type or delta variant), and disease severity strata (asymptomatic, mild-to-moderate and severe) and levels of virus-specific antibody (anti-N and anti-S) immunity after 4-6 weeks. Results: Of 79 children recruited, asymptomatic, mild-to-moderate and severe presentation was seen in 29%, 59% and 11% subjects, respectively. Wild-type and delta presented with similar disease severity. Anti-S antibody levels were higher than anti-N for both variants (wild-type or delta) (p<0.0001). Anti-S was also higher than anti-N among asymptomatic (p=0.02) and mild-to-moderate disease (p<0.0001)). Both anti-S and anti-N antibody levels were higher among children with higher virus loads [quartile (Q) 1 versus Q3, p<0.05]. Anti-S levels of wild-type were higher than Delta-infected among low (Q3) virus loads (p=0.003). Mean Ct values of wild-type (32.5) was higher than Delta infections (25.0), (p=0.0083) among mild-to-moderate disease. Conclusions: Viral load drives antibody response in children. Higher loads of Delta VOC resulted in robust antibody response in mild-to-moderate disease, not seen in severe disease. These finding are an indication of response to future SARS CoV-2 variants and could inform targeted vaccination when introduced in children.