Seasonal Influenza Vaccine (Cell-Based Quadrivalent)

Seasonal quadrivalent influenza vaccine (QIV) protects against 4 influenza strains chosen annually by WHO strain surveillance. Cell-based production (using MDCK or Vero cells instead of chicken eggs) eliminates egg adaptation mutations that reduce vaccine effectiveness. Global flu vaccine market: ~500 million doses/year; 3 major producers (CSL Seqirus ~30%, Sanofi Pasteur ~35%, GSK ~20%). Annual strain selection in February (North) and September (South) creates a 6-month production window. Cell-based manufacturing enables ~6-8 week faster response than egg-based in a pandemic. US government (CDC) distributes ~170 million doses annually for seasonal flu prevention.