r With continuing occurrence of varicella despite increasing vaccine coverage for the past 20 years, a case-based study, a case-control study, and an immunogenicity and safety study were conducted to address the impact of varicella vaccination in South Korea. Varicella patients under the age of 16 years were enrolled for the case-based study. For the case-control study, varicella patients between 12 months and 15 years of age were enrolled with one control matched for each patient. For the immunogenicity and safety study, otherwise healthy children from 12 to 24 months old were immunized with Suduvax (Green Cross, South Korea). Fluorescent antibody to membrane antigen (FAMA) varicella-zoster virus (VZV) antibody was measured before and 6 weeks after immunization. In the casebased study, the median age of the patients was 4 years. Among 152 patients between 1 and 15 years of age, 139 children received varicella vaccine and all had breakthrough infections. Clinical courses were not ameliorated in vaccinated patients, but more vaccinated patients received outpatient rather than inpatient care. In the case-control study, the adjusted overall effectiveness of varicella vaccination was 54%. In the immunogenicity and safety study, the seroconversion rate and geometric mean titer for FAMA antibody were 76.67% and 5.31. Even with increasing varicella vaccine uptake, we illustrate no upward age shift in the peak incidence, a high proportion of breakthrough disease, almost no amelioration in disease presentation by vaccination, and insufficient immunogenicity of domestic varicella vaccine. There is need to improve the varicella vaccine used in South Korea.
Varicella caused by varicella-zoster virus (VZV) is a highly infectious disease, and the secondary attack rates may reach up to 90% for susceptible household contacts. In South Korea, a live attenuated Biken Oka strain varicella vaccine was first introduced in 1988, and since then a few more imported and domestic vaccines have been on the market for different lengths of time. Among the few domestic vaccines which were developed in the early 1990s, only Suduvax (Green Cross, South Korea) is currently on the market and is the most popular varicella vaccine in South Korea. With the increase of varicella vaccine coverage in South Korea, varicella became a nationally notifiable disease, and the vaccine was mandated for universal immunization at government expense in 2005; routine varicella immunization for infants at 12 to 15 months of age was recommended. These measures should have reduced the burden of varicella in South Korea. However, the nationwide occurrence of varicella has not decreased substantially, unlike the successful experience in other countries (1-5). We report a short-term case-based study, a case-control study, and an immunogenicity and safety study to evaluate the effectiveness of varicella vaccination in South Korea.
MATERIALS AND METHODSA case-based study was conducted prospectively from August 2006 to March 2007, when 176 children with varicella who were...