Variant-Specific Viral Kinetics in Acute COVID-19

Understanding variant-specific differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral kinetics may explain differences in transmission efficiency and provide insights on pathogenesis and prevention. We evaluated SARS-CoV-2 kinetics from nasal swabs across multiple variants (Alpha, Delta, Epsilon, Gamma) in placebo recipients of the ACTIV-2/A5401 trial. Delta variant infection led to the highest maximum viral load and shortest time from symptom onset to viral load peak. There were no significant differences in time to viral clearance across the variants. Viral decline was biphasic with first- and second-phase decays having half-lives of 11 hours and 2.5 days, respectively, with differences among variants, especially in the second phase. These results suggest that while variant-specific differences in viral kinetics exist, post-peak viral load all variants appeared to be efficiently cleared by the host.Clinical Trials Registration. NCT04518410.

Automated summary

Understanding variant-specific differences in SARS-CoV-2 viral kinetics is important for explaining transmission efficiency and gaining insights on pathogenesis and prevention. In this study, we found that the Delta variant had the highest viral load and the shortest time to peak viral load among multiple variants. There were no significant differences in time to viral clearance across the variants, but differences were observed in the second phase of viral decay. These results indicate that while variant-specific differences exist, all variants appear to be efficiently cleared by the host after reaching peak viral load.