Epidemiological characteristics of varicella outbreaks in the Republic of Korea, 2016-2020.

OBJECTIVES

We described the trends and epidemiological characteristics of varicella outbreaks from 2016 to 2020 in the Republic of Korea.

METHODS

We investigated variables such as the outbreak setting, age of patients, vaccination status, and lesion count. The collected data were analyzed with the Cochrane-Armitage trend test and Kruskal-Wallis test. These statistical tests were performed using R ver. 4.0.3.

RESULTS

The number of varicella outbreaks increased from 2016 to 2018; however, after a slight decrease in the number of outbreaks in 2019, the number fell sharply in 2020. The median size of outbreaks decreased from 8 to 9 cases during 2016-2019 to 6 cases in 2020. The median duration of outbreaks was 18 days during 2016-2017, 28 days in 2018, 29 days in 2019, and 15 days in 2020. Varicella outbreaks occurred most frequently in elementary schools, and vaccination coverage of patients increased from 89.4% in 2016 to 97.2% in 2019. The median age of patients with outbreak-related varicella decreased from 8 years in 2016 to 6 years in 2020.

CONCLUSION

Significant changes were observed in the age of patients with outbreak-related varicella. Ongoing monitoring of varicella outbreaks should be conducted. Further research will be needed to measure the disease burden of varicella and enable evidence-based policy decisions.