Varicella (chickenpox) is an infectious disease caused by the highly contagious varicella zoster virus with a secondary attack rate greater than 90%. From this perspective, we aimed to establish the basis for a national varicella vaccine policy by reviewing vaccination programs and policies of countries that have introduced universal varicella vaccinations. As a result of the spread of varicella, an increasing number of countries are providing 2-dose vaccinations and universally expanding their use. In practice, the efficacy and effectiveness of vaccination differ among vaccines and vaccination programs. Optimized vaccination strategies based on each country’s local epidemiology and health resources are required. Accordingly, it is necessary to evaluate the effectiveness of varicella vaccines in different settings. Given the short-term and fragmented vaccine effectiveness evaluation in Korea, it is necessary to evaluate its effectiveness at the national level and determine its schedule based on the evidence generated through these studies.

Yoon Y, et al. J Korean Med Sci. 2020 Oct;35(46):e414. https://doi.org/10.3346/jkms.2020.35.e414

Kim YJ, et al. J Korean Med Sci. 2020 Apr;35(22):e204. https://doi.org/10.3346/jkms.2020.35.e204

Summary: Background: Data on SARS-CoV-2 transmission from a pediatric index patient to others at the school setting are limited. Epidemiologic data on pediatric COVID-19 cases after school opening is warranted. Methods: We analyzed data of the pediatric patients with COVID-19 collected from the press release of the Korea Centers for Disease Control and Prevention. Information on the school opening delay and re-opening policies were achieved from the press release from Korean Ministry of Education. Findings: The school openings were delayed three times in March 2020. Online classes started from April 9, and off-line classes started from May 20 to June 8 at four steps in different grades of students. There was no sudden increase in pediatric cases after the school opening, and the proportion of pediatric cases remained around 7.0% to 7.1%. As of July 11, 45 children from 40 schools and kindergartens were diagnosed with COVID-19 after off-line classes started. More than 11,000 students and staff were tested; only one additional student was found to be infected in the same classroom. Among those 45, 32 (71.1%) patients had available information for the source of infection. Twenty-five (25/45, 55.6%) were infected by the family members. The proportions of pediatric patients without information on infection sources were higher in older age group (middle and high school students) than in younger age group (kindergarten and elementary school students) (47.6% vs 12.5%, p =0.010). In the younger age group, 79.1% of children were infected by family members, while only 28.6% of adolescents in the older age group were infected by family members ( p <0.001). Interpretation: Korea had a successful transition from school closure to re-opening with online and off-line classes. Although partial, off-line school opening did not cause significant school-related outbreak among pediatric population although young children and adolescents may have different epidemiologic features. Funding: None.

Yoon Y, et al. J Korean Med Sci. 2023 Sep;38(40):e311. https://doi.org/10.3346/jkms.2023.38.e311

Yoon Y, et al. J Korean Med Sci. 2021 Feb;36(10):e71. https://doi.org/10.3346/jkms.2021.36.e71