Sanofi-Aventis Korea has secured regulatory approval for two trivalent influenza vaccines that exclude the long-dormant B/Yamagata strain, the Ministry of Food and Drug Safety confirmed this month.

The approval reflects a global pivot in flu vaccine composition following the apparent disappearance of B/Yamagata, which hasn’t been genetically confirmed in human circulation since early 2020. Once a mainstay of seasonal flu vaccines, the strain is now considered functionally extinct—an outcome attributed to pandemic-era public health measures.

Sanofi Korea’s updated products—Efluelda, targeting adults 65 and older, and Vaxigrip, for individuals aged six months and up—will protect against three flu strains: two influenza A subtypes (H1N1 and H3N2) and one influenza B strain from the B/Victoria lineage. The updated formulation aligns with recent recommendations from the WHO, EMA, and FDA to eliminate B/Yamagata from future flu vaccines.

For years, most flu shots have been quadrivalent, covering both B/Victoria and B/Yamagata alongside two A strains. But with no confirmed B/Yamagata cases since March 2020—and no animal reservoir to support its re-emergence—global health authorities have endorsed a transition to trivalent formulations starting with the 2025–2026 season.

The Korea Disease Control and Prevention Agency (KDCA) has also confirmed that its National Immunization Program will shift to trivalent vaccines beginning in 2025, starting with seniors and high-risk groups.