Objectives We aimed to compare epidemiologic features of second and third COVID-19 pandemic waves in South Korea. Methods Nationwide COVID-19 data was collected during the study period (May 6–December 30). The degree of social activities was also estimated using the internet searching trend analysis program for leisure-related keywords including “eating-out,” “trip,” and “get directions” (transportation). We compared the demographics, transmission chains, case fatality rates, social activity level, and public health responses between second (August 13–September 18) and third (November 4–present) waves. Results Compared to the second wave, the third wave was characterized by delayed social distancing reinforcement (3 vs. 15 days), longer duration (36 vs. > 56 days) and higher fatality rates (0.91% vs. 1.26%). There was a significant difference in transmission chains of the second and third waves of the COVID-19 pandemic (p < 0.01). During the third wave compared with the second wave, the proportion of local clusters (24.8% vs. 45.7%) was lower, while those of personal contact transmission (38.5% vs. 25.9%) and unknown routes of transmission (23.5% vs. 20.8%) were higher. Conclusion Early and timely interventions with strengthened social distancing policies should be implemented to effectively suppress and control the COVID-19 pandemic.

Serosurveillance studies reveal the actual disease burden and herd immunity level in the population. In Seoul, Korea, a cross-sectional investigation showed 0.07% anti-severe acute respiratory syndrome coronavirus-2 antibody seropositivity among 1,500 outpatients of the university hospitals. Low seroprevalence reflects well-implemented social distancing. Serosurveillance should be repeated as the pandemic progresses.

Although some intravenous drugs have been used to treat coronavirus disease 2019 (COVID-19), no effective antiviral agents are currently available in the outpatient setting. We aimed to evaluate the efficacy and adverse events of 14-day ciclesonide treatment vs. standard care for patients with mild-to-moderate COVID-19. A randomized, open-label, multicenter clinical trial of ciclesonide inhalers was conducted in patients with mild-to-moderate COVID-19. Patients were enrolled within 3 days of diagnosis or within 7 days from symptom onset and randomly assigned to receive either ciclesonide (320 µg inhalation twice per day for 14 days) or standard care. The primary endpoint was the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) eradication rate on day 14 from study enrollment. Clinical status was assessed once daily, and serial nasopharyngeal viral load was evaluated by quantitative reverse transcription polymerase chain reaction. There were 35 and 26 patients in the ciclesonide and standard care groups, respectively. The SARS-CoV-2 eradication rate at day 14 was significantly higher in the ciclesonide group (p = 0.021). In multivariate analysis, SARS-CoV-2 negative conversion within 14 days was 12 times more likely in the ciclesonide group (95% confidence interval, 1.187–125.240). Additionally, the clinical failure rate (high-flow nasal oxygen therapy or mechanical ventilation) was significantly lower in the ciclesonide group (p = 0.034). In conclusion, ciclesonide inhalation shortened SARS-CoV-2 viral shedding duration, and it may inhibit the progression to acute respiratory failure in patients with mild-to-moderate COVID-19. Clinical Trial Registration NCT04330586.

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Since February 26, 2021, when vaccination against coronavirus disease 2019 (COVID-19) began in South Korea, patients who visited the Korea University Guro Hospital with suspected adverse events after COVID-19 vaccination were monitored actively with interest. We encountered five unusual cases of polyarthralgia and myalgia syndrome in patients who received the ChAdOx1 nCOV-19 (AstraZeneca) vaccine. The patients (median age 67 years) were not previously diagnosed with arthropathy and rheumatologic diseases. They developed fever, myalgia, joint pain, and swelling three to seven days after vaccination. The symptoms persisted for up to 47 days despite antipyretic treatment. Arthralgia occurred in multiple joints, including small and large joints. A whole-body Technetium-99m methylene diphosphonate bone scan revealed unusual uptakes in the affected joints. Non-steroidal anti-inflammatory drugs with or without prednisolone relieved the symptoms of all patients. Further monitoring is required to clarify the long-term prognosis of this syndrome.

Face masks are used to protect the wearer from harmful external air and to prevent transmission of viruses from air exhaled by potentially infected wearers to the surrounding people. In this study, we examined the potential utility of masks for collecting viruses contained in exhaled breath and detected the collected viruses via various molecular tests. Using KF94 masks, the inner electrostatic filter was selected for virus collection, and an RNA extraction protocol was developed for the face mask. Virus detection in worn mask samples was performed using PCR and rolling circle amplification (RCA) tests and four different target genes (N, E, RdRp, and ORF1ab genes). The present study confirmed that the mask sample tests showed positive SARS-CoV-2 results, similar to the PCR tests using nasopharyngeal swab samples. In addition, the quantity of nucleic acid collected in the masks linearly increased with wearing time. These results suggest that samples for SARS-CoV-2 tests can be collected in a noninvasive, quick, and easy method by simply submitting worn masks from subjects, which can significantly reduce the hassle of waiting at airports or public places and concerns about cross-infection. In addition, it is expected that miniaturization technology will integrate PCR assays on face masks in the near future, and mask-based self-diagnosis would play a significant role in resolving the pandemic situation.

There is insufficient data on the longevity of immunity acquired following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to evaluate the duration of SARS-CoV-2-specific humoral and cellular immunity according to the clinical severity of coronavirus disease 2019 (COVID-19). The study population comprised asymptomatic (n=14), symptomatic/non-pneumonic (n=42), and pneumonic (n=41) patients. The anti-SARS-CoV-2 IgG and neutralizing antibody (NAb) titers lasted until six months after diagnosis, with positivity rates of 66.7% and 86.9%, respectively. Older age, prolonged viral shedding and accompanying pneumonia were more frequently found in patients with sustained humoral immunity. SARS-CoV-2 specific T-cell response was strongly observed in pneumonic patients and prominent in individuals with sustained humoral immunity. In conclusion, most (&gt; 85%) patients carries NAb until six months after diagnosis of SARS-CoV-2 infection, providing insights for establishing vaccination strategies against COVID-19.