Seroepidemiological Study of Varicella Zoster Virus in Korea, 2023

Seroprevalence studies monitor changes in the immune status of populations. During the coronavirus disease 2019 (COVID-19) pandemic, public health measures such as social distancing and mask-wearing led to significant changes in the epidemiology and transmission patterns of many infectious diseases. In the post-pandemic period, outbreaks of various infectious diseases have been reported globally. In this context, this study evaluated changes in varicella zoster virus (VZV) seroepidemiology in the Republic of Korea after the COVID-19 pandemic.

Residual serum samples were collected from specimens referred to Seoul Clinical Laboratories in 2023. Serum samples were collected after anonymization, with all identifiable information excluded except for date, age, sex, and region. Samples were collected evenly by age group in 5-year intervals. The evaluation of anti-VZV IgG antibodies was performed using a chemiluminescence immunoassay analyzer (Liaison^®XL; Diasorin).

The study population comprised 995 participants including 581 males and 414 females. The overall VZV IgG seropositivity rate was 82.9%. The seropositivity rates of VZV IgG antibodies were 88.1% in males and 75.6% in females. VZV IgG seroprevalence showed variations across different age groups. VZV IgG seropositivity was 80% in the 1-4 year age group, declined to 53% in the 5-9 year age group, and reached its lowest at 43% in 10-14 year-olds. Seropositivity rates steadily increased from 71% in the 15-19 year-olds, to 85% in the 25-29 year group, and exceeded 95% in subjects ≥ 40 year of age.

Seropositivity rates in children (5-19 year) and adults (20-39 year) were lower than in previous studies in the Republic of Korea, likely due to reduced community exposure to varicella during the pandemic. These findings highlight a potential need to reinforce infection control measures and vaccination policies to address vulnerable age groups.