Background: In this study, the prevalence and persistence of anti-SARS-CoV-2 (severe acute respiratory syndrome-coronavirus) IgG was evaluated in volunteers 90 days after COVID-19 (coronavirus disease 2019) diagnosis by correlating response dynamics with clinical conditions, IL-1β and IL-6 cytokine levels, epidemiological characteristics, and disease severity. Methods: The study recruited 200 volunteers aged 18 years or older of both sexes diagnosed with COVID-19. ELISA testing was performed to detect IgG persistence and cytokine levels in 135 individuals with a previous serological test at the time of COVID-19 diagnosis.Results: Among the 135 individuals who underwent a previous serological test for anti-SARS-CoV-2 antibody and provided a new blood sample 90 days after the first examination, 125 showed reactivity to IgG (92.6%). Of the 125 individuals with detectable IgG in the first test, 69.6% showed persistence of this antibody after 90 days; however, in 10 (30.4%) individuals, IgG was nonreactive in the second evaluation. The frequency of all reported symptoms was higher in individuals who maintained IgG persistence after 90 days of symptoms, and no relationship with cytokine levels was observed. Conclusions: The results of the present study show a high frequency of loss of anti-SARS-CoV-2 IgG antibodies within three months after COVID-19 diagnosis in the Brazilian Amazon.