Clinical spectrum of SARS-CoV-2 infection and protection from symptomatic re-infection.

Background There are few data on the full spectrum of disease caused by SARS-CoV-2 infection across the lifespan from community-based or non-clinical settings. Methods We followed 2,338 people in Managua, Nicaragua, aged 0 to 94 years old from March 2020 through March 2021. SARS-CoV-2 infection was identified through real-time reverse transcription polymerase chain reaction (RT-PCR) or through enzyme-linked immunosorbent assay (ELISA). Disease presentation was assessed at the time of infection or retrospectively by survey at the time of blood collection. Results There was a large epidemic that peaked between March-August 2020. In total, 129 RT-PCR-positive infections were detected, for an overall incidence rate of 5.3 infections per 100 person-years (95% CI: 4.4-6.3). Seroprevalence was 56.7% (95%CI: 53.5%-60.1%) and was consistent from age 11 through adulthood but was lower in children aged ≤10 years. Overall, 31.0% of the infections were symptomatic, with 54.7% mild, 41.6% moderate, and 3.7% severe. There were two deaths that were likely due to SARS-CoV-2 infection, yielding an infection fatality rate of 0.2%. Antibody titers exhibited a J-shaped curve with respect to age, with the lowest titers observed among older children and young adults and the highest among older adults. When compared to SARS-CoV-2 seronegative individuals, SARS-CoV-2 seropositivity at the midyear sample was associated with 93.6% protection from symptomatic re-infection (95%CI: 51.1-99.2%). Conclusions This population exhibited a very high SARS-CoV-2 seropositivity with lower-than-expected severity, and immunity from natural infection was protective against symptomatic re-infection.