GC Biopharma’s chickenpox vaccine, Barycela Inj., is set to enter a Phase 3 clinical trial in South Korea to confirm evidence supporting a two-dose schedule. The trial is part of the company’s preparations for global markets as prevention strategies increasingly shift from a single injection to a two-dose approach.
GC Biopharma announced on July 2 that South Korea’s Ministry of Food and Drug Safety (MFDS) has approved the Phase 3 clinical trial protocol (IND) for a two-dose Barycela Inj. regimen.
With this approval, GC Biopharma will assess in South Korea whether administering Barycela Inj. twice to children produces an adequate immune response and whether any safety issues emerge. After securing these clinical results, the company plans to seek marketing authorization for the two-dose regimen in South Korea and major Southeast Asian countries.
The trial expands a global study already underway in Thailand and Vietnam by adding South Korea to the protocol. It will enroll 474 healthy children between the ages of 12 months and 12 years and is designed to directly compare immunogenicity and safety results with Merck (MSD)’s chickenpox vaccine, Varivax.
Shifting toward a Two-Dose National Immunization Standard
Chickenpox is a common infectious disease in children, but it is highly contagious and can spread quickly in group settings such as daycare centers, kindergartens, and schools.
"Breakthrough infections," in which individuals become infected despite being vaccinated, remain a critical variable in global immunization strategy. While a single dose helps reduce the risk of severe chickenpox, cases have been reported in which immunity wanes over time or outbreaks are not sufficiently prevented. Consequently, many countries are transitioning to a mandatory two-dose system.
The United States, Canada, and Japan, among others, have already implemented a two-dose chickenpox vaccination schedule. According to a review of global chickenpox immunization programs published in Clinical and Experimental Pediatrics, 28 countries were utilizing a universal two-dose schedule for infants and young children at the time of the survey. The paper noted that a two-dose regimen is highly meaningful in reducing both chickenpox severity and the incidence of breakthrough infections.
Expanding the Global Reach of the MAV/06 Strain
Barycela Inj. is a live attenuated chickenpox vaccine based on the proprietary MAV/06 strain, which GC Biopharma developed in-house in 1993. The global chickenpox vaccine market has long been dominated by Oka-lineage strains developed in Japan, of which Merck’s Varivax is a representative example.
GC Biopharma stated that the basis for using the MAV/06 strain to support overseas clinical trials and regulatory filings broadened significantly after it was officially included in the World Health Organization (WHO) chickenpox vaccine position paper. Given that Oka-lineage vaccines have traditionally controlled the global market, the explicit mention of the MAV/06 strain in an official WHO document serves as a major reference point for Barycela Inj.’s international expansion.
However, inclusion in a WHO position paper does not automatically lead to immediate regulatory approvals in individual countries or immediate updates to local immunization schedules. National vaccination policies are determined by independently weighing factors such as country-specific disease burden, cost-effectiveness, vaccine supply conditions, and localized clinical data. The MFDS approval is seen as a vital step to build the clinical evidence required for the official authorization of a two-dose Barycela Inj. regimen.
After completing the multinational trial, GC Biopharma plans to pursue marketing authorization for the two-dose regimen across South Korea and major Southeast Asian markets, targeting full entry into the global two-dose chickenpox vaccine market by 2028.
"The two-dose clinical trial for Barycela Inj. is a key milestone to enhance the asset value of our vaccine portfolio," said Lee Jae-woo, Head of Development at GC Biopharma. "We aim to lower the risk of breakthrough infections in children while expanding the vaccine's utility in both global public procurement and private healthcare markets."
