SARS-CoV-2 sero-surveillance after the first and second waves of the epidemic in Panama

IntroductionIn the context of the ongoing global SARS-CoV-2 pandemic and potential future viral epidemics, seroepidemiological studies are essential for understanding epidemic dynamics. Panama, a country with a strategic geographic position that serves as a regional hub for international travel and commerce. As such, understanding local transmission patterns is critical for developing evidence based on interventions that can effectively anticipate and mitigate emerging viral threats. MethodologyWe conducted a population-based cross-sectional study in the provinces of Panama and Panama Oeste, targeting the 10 townships with the highest cumulative COVID-19 incidence. A multi-stage cluster sampling strategy was employed using the 2010 National Housing Framework. The first survey was conducted from November 30 to December 4, 2020. A follow-up survey was carried out from June 14 to July 10, 2021, to assess seroconversion and seroreversion. Serum samples were analyzed using two electrochemiluminescence immunoassays (Cobas and Vitros) to detect SARS-CoV-2-specific IgG, IgM, and IgA. We estimated the effective reproduction number (Rt) and fitted modified Poisson regression models to identify risk factors associated with seropositivity. ResultsA total of 2198 participants were recruited in the first round, and 547 were successfully followed up in the second round. SARS-CoV-2 seroprevalence increased from 24.7% (95% CI: 23.0-27.0%) in the first round to 66.2% (95% CI: 62.0 - 70.0%) in the second. The seroconversion rate was 42.9% (95% CI: 38.0 - 47.0%), while seroreversion was rare (0.9%; 95% CI: 0.3 - 2.0%). The most parsimonious multivariable model identified Indigenous ethnicity, contact with a confirmed case, cohabiting with an infected household member, and prior COVID-19 diagnosis as significant risk factors for seropositivity. In contrast, higher education, belonging to other ethnic groups, and consistent mask use at work were protective factors. ConclusionsSARS-CoV-2 transmission persisted in Panama despite strict public health interventions. Household transmission, particularly among Indigenous and socioeconomically vulnerable populations, was a major driver of infection. Higher education and adherence to preventive behaviors emerged as protective factors. These findings emphasize the importance of targeted, equity focused strategies to strengthen epidemic control in Panama and comparable settings.