Background Serological evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an alternative that allows us to determine the prevalence and dynamics of this infection in populations. The goal of this study was to determine the clinical and sociodemographic dynamics of SARS-CoV-2 infection in a region of the Colombian Caribbean. Methods Between July and November 2020, a cross-sectional observational study was carried out in Córdoba, located in northeast Colombia in the Caribbean area. Eight municipalities with the largest populations were chosen and 2564 blood samples were taken. A commercial enzyme-linked immunosorbent assay was used with the recombinant protein antigen N of SARS-CoV-2. The people included in the study were asked for sociodemographic and clinical data, which were analysed by statistical methods. Results A seroprevalence of 40.8% was obtained for SARS-CoV-2 in the Córdoba region. In the bivariate analysis, no differences were observed in seropositivity against SARS-CoV-2 for gender or age range (p>0.05). Higher seropositivity was found in low socio-economic status and symptomatic patients (p<0.0001). A total of 30.7% of the asymptomatic patients were seropositive for SARS-CoV-2, which could be linked to the spread of this infection. In the multivariate analysis, seroconversion was related to poverty and clinical manifestations such as anosmia and ageusia (p<0.05). Conclusions The high seropositivity in Córdoba is due to widespread SARS-CoV-2 in this population. The relationship between seropositivity and socio-economic status suggests a higher exposure risk to the virus caused by informal economic activities in low-income groups. Clinical manifestations such as anosmia and ageusia could be clinical predictors of infection by the new emergent coronavirus.

There are many doubts about the SARS-CoV-2 immune response's length, and it is unknown whether those patients may exhibit different kinetics in the secretion of IgG anti-SARS-CoV2 according to the severity of their infection. This research aimed to evaluate IgG antibodies' kinetics and persistence against the SARS-CoV-2 Spike protein in a group of COVID-19 patients with different clinical disease presentations in the Colombian Caribbean region. Two blood samples were taken. The first one was at the first surge in August 2020; the second was six months later, February 2021. The study showed a decrease of 61.1% in their median of IgG antibodies after six months (P > 0.0001). According to the clinical form of COVD-19, the patients that required hospitalization (moderate or severe) COVD-19 showed a lower secretion of IgG against SARS-CoV2 and a higher negative seroconversion for IgG 69.2% in the second serological evaluation (P < 0.05). Thus, the drop of antibodies-SARS-CoV-2 is typical in all the clinical forms of COVID-19. It is worrisome in patients with moderate or severe clinical forms. The evaluation of natural immunity is mandatory to define the vaccination strategy mainly in patients that suffered complicated forms of COVID-19.

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