A One-Year Follow-Up Cohort Study of Ambulatory Patients with SARS-CoV-2 Infection: The Landscape in Mexico.

Background and Objectives: SARS-CoV-2 is the pathogen that causes COVID-19 disease. Although the rate of COVID-19 reinfection is significant, the possible factors associated with this condition remain to be fully elucidated. The aim of the study was to identify clinical and serological factors associated with SARS-CoV-2 reinfection. Materials and Methods: We followed up on 120 patients with mild COVID-19 for one year. Various clinical data were collected, and serum levels of IgG anti-SARS-CoV-2 Spike antibodies were tested on days 21, 60, 90, and 180. The diagnosis of COVID-19 was based on symptomatology and the detection of viral RNA in nasal swabs using real-time PCR. Results: We observed eleven episodes of reinfection. Although no clinical or demographic characteristics were associated with reinfection, significantly higher levels of anti-Spike antibodies and a seropositive status at day 90 were significantly associated with the absence of reinfection. Moreover, the symptoms during the COVID-19 episode associated with seropositivity at day 90 were mainly headache, sneezing, anosmia, and runny nose. Conclusions: SARS-CoV-2 reinfection is not associated with the clinical or demographic characteristics of COVID-19 patients. Furthermore, our findings suggest that the presence and levels of IgG anti-Spike antibodies at day 90 of infection play a protective role against reinfection. Serological immunity at day 90 influences the response to vaccination. [ABSTRACT FROM AUTHOR]