**1. Introduction**

As of mid-December 2020, the World Health Organization has reported nearly 74 million confirmed cases of COVID-19 and 1.6 million associated deaths worldwide [1]. In South Korea, there have been 48,570 confirmed cases and 659 associated deaths since COVID-19 emerged in Wuhan, China, in December 2019, and was identified as a new coronavirus in January 2020 [1,2]. By mid-February 2020, the number of cases in South Korea began to spread quickly, with the outbreak centered in the city of Daegu, southeast of Seoul [3]. The South Korean government implemented protective measures against the spread of COVID-19, including a national infectious disease plan stemming from the 2015 MERS outbreak; nationwide contact tracing efforts; and a ban on the export of face masks [4,5]. Such policies that encourage protective behaviors such as social distancing have been found to be effective in reducing the spread of COVID-19 [6]. Many of these social distancing measures, such as school closures and the subsequent transition to online learning, greatly affect adolescents, and researchers have found that the continued spread of COVID-19 has many deleterious effects on adolescents' mental, physical, and socioemotional health [7–13]. Therefore, it is of interest to examine the extent to which adolescents engage in protective behaviors against the spread of COVID-19, such as staying home and being more diligent about hygiene, and what determinants influence such behaviors, so that the spread of COVID-19 may be reduced [14].

**Citation:** Lee, J.; Allen, J.; Lim, H.; Choi, G. Determinants of Behavioral Changes Since COVID-19 among Middle School Students. *Healthcare* **2021**, *9*, 75. https://doi.org/ 10.3390/healthcare9010075

Received: 22 December 2020 Accepted: 12 January 2021 Published: 14 January 2021

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