J Korean Med Sci.  2022 Aug;37(34):e260. 10.3346/jkms.2022.37.e260.

Trends in Confirmed COVID-19 Cases in the Korean Military Before and After the Emergence of the Omicron Variant

• Shin DH
• Jang H
• Lee S
• Choi BS
• Kim D
• Oh HS

• KMID: 2532755
• DOI: http://doi.org/10.3346/jkms.2022.37.e260

Abstract

Background
Due to the higher transmissibility and increased immune escape of the omicron variant of severe acute respiratory syndrome coronavirus 2, the number of patients with coronavirus disease 2019 (COVID-19) has skyrocketed in the Republic of Korea. Here, we analyzed the change in trend of the number of confirmed COVID-19 cases in the Korean military after the emergence of the omicron variant on December 5, 2021.
Methods
An interrupted time-series analysis was performed of the daily number of newly confirmed COVID-19 cases in the Korean military from September 1, 2021 to April 10, 2022, before and after the emergence of the omicron variant. Moreover, the daily number of newly confirmed COVID-19 cases in the Korean military and in the population of Korean civilians adjusted to the same with military were compared.
Results
The trends of COVID-19 occurrence in the military after emergence of the omicron variant was significantly increased (regression coefficient, 23.071; 95% confidence interval, 16.122–30.020; P < 0.001). The COVID-19 incidence rate in the Korean military was lower than that in the civilians, but after the emergence of the omicron variant, the increased incidence rate in the military followed that of the civilian population.
Conclusion
The outbreak of the omicron variant occurred in the Korean military despite maintaining high vaccination coverage and intensive non-pharmacological interventions.

Keyword

COVID-19; Military Personnel; SARS-CoV-2 Omicron Variant; Interrupted TimeSeries Analysis

Figure

• 

  Fig. 1 Timeline of COVID-19-related events in the Korean military, including the mass vaccination program.COVID-19 = coronavirus disease 2019.aMilitary personnel who received the first dose of ChAdOx1 nCoV-19 vaccine were given a second dose of ChAdOx1 nCoV-19 or BNT162b2 vaccine, depending on the individual’s choice. Excluding the untracked units under the direct control of the Ministry of National Defense, which make up 4.4% of the military, mass vaccination was performed as follows: ChAdOx1 nCoV-19, 0.67%; BNT162b2, 78.12%; Ad.26.COV2.S, 0.57%; and heterologous vaccination (ChAdOx1 nCoV-19 followed by BNT162b2), 20.64%.bAll military personnel received the BNT162b2 vaccine as the third dose of vaccine. Individuals who were vaccinated in civilian institutions were considered as having missing data.

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  Fig. 2 Daily number of newly confirmed COVID-19 cases in Korean military and in the population of Korean civilians adjusted to the military populationa. The second graph shows the change in the proportion of each variantc among confirmed cases among the Korean military and civilian populations over time.COVID-19 = coronavirus disease 2019, CI = confidence interval.aThe trends in daily confirmed COVID-19 cases in Korean civilians adjusted to same population with the military are shown.bThe change in trend in the daily number of confirmed COVID-19 cases in military was analyzed before and after December 5, 2021, when the first case with the omicron variant was detected in the Korean military. The trend was analyzed using segmented regression analysis of interrupted time-series.cThe Armed Forces Medical Research Institute conducted variant tests on a mean of 16 samples (standard deviation: 13) of personnel with confirmed COVID-19 per week. The data on Korean civilians was obtained from the data published weekly by the Korea Disease Control and Prevention Agency (uniform resource locator: https://www.kdca.go.kr/contents.es?mid=a20107040000).

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