Abstract; ; Background; An estimated 65% of the US population had at least two SARS-CoV-2 infections by November 2022, but the impact of prior infection on disease course in subsequent infections has been debated. Population-level studies can yield conflicting results due to biases that arise from differences in differences in infection history, vaccination status, and patient characteristics. Examining the dynamics of SARS-CoV-2 infections at the individual level can help adjust for these biases.; ; ; Methods; Using a convenience sample of 94,812 longitudinal RT-qPCR measurements from samples each taken from a combined anterior nares/oropharyngeal swab, we compared the SARS-CoV-2 viral kinetics of first vs. second infections, adjusting for viral variant, vaccination status, and age. We characterized the kinetics of these infections by fitting a hierarchical Bayesian piecewise linear model to the viral concentration measurements.; ; ; Results; Relative to first infections, second infections usually featured a faster clearance time (5.1 days, 95% CI (4.7, 5.7) vs. 8.8 days (7.8, 9.8) in first infections), especially in individuals who received a vaccine dose between their first and second infection. Furthermore, a person’s relative (rank-order) viral clearance time, compared to others infected with the same variant, was similar across first and second infections (Spearman correlation: 0.475, p < 0.0001); that is, individuals who had a relatively fast clearance time in their first infection tended to also have a relatively fast clearance time in their second infection.; ; ; Conclusion; Like vaccination, immunity from a prior SARS-CoV-2 infection shortens the duration of subsequent acute SARS-CoV-2 infections principally by reducing viral clearance time. Additionally, there appears to be an inherent element of the immune response, or some other host factor, that shapes a person’s relative ability to clear SARS-CoV-2 infection that persists across sequential infections.; ; ; Disclosures; Stephen Kissler, PhD, ModernaTx: Advisor/Consultant Christina Mack, PhD, IQVIA: Full time employee of IQVIA which is in paid contractual relationship with bio pharma companies. Caroline Tai, PhD, Evidation Health: Stocks/Bonds-IQVIA: Employee Yonatan H. Grad, MD, PhD, Day Zero Diagnostics: Board Member-GSK: Advisor/Consultant;
