COVID-19 spread rapidly in 2020. To decrease its transmission rate, governments worldwide implemented social distancing. It has transformed people's physical and social activities. Such changes, differently influenced by age, might affect the incidence of traumatic injury.

The impact of social distancing on traumatic injuries can influence differently by age.

Nationwide randomized stratified sampling data (2018 to 2020, 1 million people per year) from Korean National Health Insurance Sharing Service were used. In this period, 364,690 patients with traumatic injuries were analyzed. People were grouped by age into 0–4, 5–19, 20–64, and≥65years. The incidence of traumatic injuries was compared between periods of social distancing and no social distancing. Social distancing levels, injured body parts, injury types, hospitalization rate, total medical cost per patient, weather, temperature, and holidays were also included for detailed analysis.

Only the 5–19 age group showed the significant interaction of social distancing and traumatic injury. In this group, as the social distancing level increased, the injury incidence decreased especially during the spring and autumn semesters. However, the proportion of injuries requiring hospitalization and total medical cost per patient increased.

Social distancing significantly affects the incidence of traumatic injuries for schooler (5–19years). Considering that the incidence changed during these semesters, the restriction of school attendance, due to social distancing, may have caused the decrease. Reduced trauma in this group seems to be related to decrease of mild trauma, considering the hospitalization rate and total medical costs.

III, retrospective cohort study.