ABSTRACT
Background. Much of the worlds population has been infected with SARS-CoV-2. Thus, infection-induced immunity will play a critical role in future SARS-CoV-2 transmission. We investigated the impact of immunity from prior infection on viral shedding duration and viral load.Methods. We conducted a household cohort study in Managua, Nicaragua with an embedded transmission study that closely monitors participants regardless of symptom status. Real-time reverse-transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assays (ELISAs) were used to measure infections and seropositivity, respectively. Blood samples were collected in Feb/March and Oct/Nov 2020 and 2021, and surrounding household intensive monitoring periods. We used accelerated failure time models to compare shedding times. Participants vaccinated [≥]14 days prior to infection were excluded from primary analyses.Results. There were 600 RT-PCR-confirmed SARS-CoV-2 infections between May 1, 2020 and March 10, 2022 with ELISA data prior to infection. Prior infection was associated with 48% shorter shedding times, event time ratio (ETR) 0.52 (95% CI: 0.39-0.69, mean shedding: 13.7 vs 26.4 days). A 4-fold higher anti-SARS-CoV-2 spike titer was associated with 17% shorter shedding (ETR 0.83, 95% CI: 0.78-0.90). Similarly, maximum viral loads (lowest CT) were lower for previously infected individuals (mean CT 29.8 vs 28.0, p = 4.02x10-3). Shedding was shorter in previously infected adults and children [≥]10 years, but not in children 0-9 years; there was little difference in CT levels for previously infected vs naive adults above age 60.Conclusions. Prior infection-induced immunity was associated with shorter viral shedding and lower viral loads.Funding: This work was supported by the National Institute for Allergy and Infectious Diseases at the National Institute of Health [award no. R01 AI120997 to A.G., and contract nos. HHSN272201400006C and 75N93021C00016 to A.G.], and a grant from Open Philanthropy.