Cross-Sectional Study of Varicella Zoster Virus Immunity in Healthy Korean Children Assessed by Glycoprotein Enzyme-Linked Immunosorbent Assay and Fluorescent Antibody to Membrane Antigen Test

Abstract

The prevalence of varicella is especially high among children in the age group of 4–6 years in South Korea, regardless of vaccination. We investigated the immune status of healthy children enrolled in day-care centers and compared pre- and post-vaccination immunity. Antibody titers were measured using a glycoprotein enzyme-linked immunosorbent assay (gpEIA) kit, and the seroconversion rate was assessed using a fluorescent antibody to membrane antigen (FAMA) test. Among 541 vaccinated children, 109 (20.1%) had breakthrough varicella. However, 13 (72.2%) of the 18 unvaccinated children had a history of varicella. The gpEIA geometric mean titers (GMTs) of pre- and 5 weeks post-vaccination in 1-year-old children were 14.7 and 72 mIU/mL, respectively, and the FAMA seroconversion rate was 91.1%. The gpEIA GMTs of 2-, 3-, 4-, 5-, and 6-year-old children were 104.1, 133.8, 223.5, 364.1, and 353.0 mIU/mL, respectively. Even though the gpEIA GMT increased with age, the pattern of gpEIA titer distribution in 4- to 6-year-old vaccinees without varicella history represented both waning immunity and natural boosting immunity. These results suggest that some vaccinees are vulnerable to varicella infection. Therefore, it is necessary to consider a two-dose varicella vaccine regimen in South Korea.

Seroprevalence of Varicella-Zoster Virus and Measles among Healthcare Workers in a Tertiary Medical Center in Korea

“…Conversely, this might have caused an improvement in the seroprevalence of VZV because the varicella vaccination in the NIH program was included in 2005. However, uncertainties still exist because breakthrough infections have been reported, especially in one dose-vaccinated population [9,[39][40][41]. Therefore, continuous evaluation of the seroprevalence of VZV is required to determine the policies of healthcare facilities.…”

Cross-reactive humoral immunity of clade 2 Oka and MAV/06 strain-based varicella vaccines against different clades of varicella–zoster virus

“… 7 It is well known that live-attenuated varicella vaccine induces tenfold less immunity than the wild-type virus. 8 , 9 However, it is unclear whether vaccine immunogenicity is influenced by amino acid substitutions in vaccine-specific sites.…”

“…The FAMA test is considered to be a more reliable protective immunogenicity test than the neutralization test because of the cell-associated nature of VZV. 9 , 14 …”