Analyses of Confirmed COVID-19 Cases Among Korean Military Personnel After Mass Vaccination

Abstract

Background The military was one of the first groups in Korea to complete mass vaccination against the coronavirus disease 2019 (COVID-19) due to their high vulnerability to COVID-19. To confirm the effect of mass vaccination, this study analyzed the patterns of confirmed cases within Korean military units. Methods From August 1 to September 15, 2021, all epidemiological data regarding confirmed COVID-19 cases in military units were reviewed. The number of confirmed cases in the units that were believed to have achieved herd immunity (i.e., ≥ 70% vaccination) was compared with the number of cases in the units that were not believed to have reached herd immunity (< 70% vaccination). Additionally, trends in the incidence rates of COVID-19 in the military and the entire Korean population were compared. Results By August 2021, 85.60% of military personnel were fully vaccinated. During the study period, a total of 174 COVID-19 cases were confirmed in the 39 units. More local transmission (herd immunity group vs. non-herd immunity group [%], 1 [0.91] vs. 39 [60.94]) and hospitalizations (12 [11.01] vs. 13 [27.08]) occurred in the units that were not believed to have achieved herd immunity. The percentage of fully vaccinated individuals among the confirmed COVID-19 cases increased over time, possibly due to the prevalence of the delta variant. Nevertheless, the incidence rate remained lower in military units than in the general Korean population. Conclusion After completing mass vaccination, the incidence rates of COVID-19 infection in the military were lower than those in the national population. New cluster infections did not occur in vaccinated units, thereby suggesting that herd immunity has been achieved in these military units. Further research is needed to determine the extent to which levels of non-pharmacological intervention can be reduced in the future.

A Historical Review of Military Medical Strategies for Fighting Infectious Diseases: From Battlefields to Global Health

“…Even in the Bolivian military, the rate of infection is higher than in the civilian population (2.5% vs. 1.26%, p < 0.0000001), whereas the rate of mortality is significantly lower (1.9% vs. 6.19%, p < 0.0000001) [ 235 ]. The rate of infection even in the Brazilian military is higher than in the civilian population [ 236 ], whereas the opposite is observed in the Korean military [ 237 ], thus confirming that the rate of infection may depend on many variables, including the coverage of the vaccination in the military compared with the general population. Moreover, despite the vaccine’s effectiveness against severe disease, the protection against infection seems to be quite limited, in particular for some types of viral variants of concern; thus, the research is actively engaged in developing more effective vaccines, possibly a “universal” vaccine [ 238 ], such as the one that is desirable to obtain even for influenza [ 239 ].…”

Multi-Faceted Analysis of COVID-19 Epidemic in Korea Considering Omicron Variant: Mathematical Modeling-Based Study

“… 9 10 Vaccination remains a key intervention strategy as it offers protection against hospitalization. 6 11 12 13 Furthermore, booster shots can provide a substantial increase in protection against symptomatic infection. 6 7 14 15 The development of safe and effective oral antiviral drugs can significantly impact control measures for COVID-19.…”

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

“…In a previous study, we reported that the incidence rates of COVID-19 infection in the Korean military were lower than those in the general Korean population, due to mass vaccination of COVID-19 conducted from July 2021 to early August 2021. 5 However, after the omicron variant became dominant in January 2022, the number of confirmed COVID-19 cases skyrocketed among military personnel, as it did among Korean civilians. During this period, to prevent the spread of the disease, the military maintained strict non-pharmacological interventions (NPI), such as performing proactive real-time reverse transcription polymerase chain reaction (PCR) testing and applying prolonged isolation guidelines.…”