Seroprevalence of severe acute respiratory syndrome coronavirus 2 antibodies during the third wave of coronavirus disease in the Seoul metropolitan area of Korea.

Objectives: After the third wave of coronavirus disease (COVID-19), by mid-February 2021, approximately 0.16% of the population was confirmed positive, which appeared to be one of the lowest rates worldwide at that time. However, asymptomatic transmission poses a challenge for COVID-19 surveillance. Therefore, a community-based serosurvey of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was conducted to understand the effectiveness of Korea's strong containment strategy. Methods: We collected 5,002 residual sera samples from January 30 to March 3, 2021 from 265 medical facilities in Seoul, 346 in Kyunggi-do' and 57 in Incheon. Among them, 60 samples from tertiary institutions were excluded. We defined the sub-regions according to the addresses of the medical facilities where the specimens were collected. Elecsys Anti-SARS-CoV-2 was used for the screening test, and positivity was confirmed using the SARS-CoV-2 sVNT Kit. Prevalence was estimated using sampling weight and the Wilson score interval for a binomial proportion with a 95% confidence interval. Results: Among the 4,942 specimens, 32 and 25 tested positive for COVID-19 in the screening and confirmatory tests, respectively. The overall crude prevalence of SARS-CoV-2 antibody was 0.51%. The population-adjusted overall prevalence was 0.55% in women and 0.38% in men. The region-specific estimation was 0.67% and 0.30% in Gyeonggi-do and Seoul, respectively. No positive cases were detected in Incheon. Conclusion: The proportion of undetected cases in South Korea remains low. Therefore, an infection control strategy with exhaustive tracing and widespread pre-emptive testing appears to be effective in containing the spread of the virus in the community.

Generic Logic Model for Coronavirus Disease-2019 Responses Based on the South Korean Experience.

BACKGROUND: As the global coronavirus disease-2019 (COVID-19) pandemic continues, many countries have implemented public health policies, such as lockdowns and physical distancing measures, to prevent its spread. South Korea's response to COVID-19, which prevented an increase in confirmed cases and increased resilience, has been considered very effective. PURPOSE: To analyze Korea's response to COVID-19 in 2020 and develop a logic model to evaluate performance effectiveness in follow-up studies. METHODS: By content analysis of Korea Disease Control and Prevention Agency (KDCA) press releases, we defined the problems and identified the causes of the health and social effects of the COVID-19 outbreak. Next, we created a problem tree and developed a logic model that comprised inputs, activities, outputs, outcomes, and impacts. Finally, we held expert consultations to obtain expert opinions regarding the logic model and to ensure the model's validity. RESULTS: South Korea's COVID-19 response policy mitigated the social and health impacts. The 2020 COVID-19 responses had four outcomes (identifying cases on time, preventing transmission of coronavirus infection, effective treatment of COVID-19 cases, protecting public resilience and well-being) and 12 outputs; South Korea conducted 32 activities. CONCLUSION: The results can be a practical reference for managing problems faced in other countries. Korean policy may be of interest in the future for international decision-makers in charge of policy enforcement and those who may be called on to respond to new infectious diseases.