Does the influenza vaccine contain egg protein?

Influenza Vaccines Contain Egg Protein

Yes, most influenza vaccines contain small amounts of residual egg protein because the vaccine viruses are typically grown in embryonated hens' eggs. 1

Egg Content in Influenza Vaccines

Manufacturing Process

• Influenza vaccines are typically made from viruses grown in embryonated chicken eggs
• After growth, the viruses are harvested, purified, and inactivated (killed) for use in vaccines 1
• The purification process removes most, but not all, egg proteins

Amount of Egg Protein

• The amount of residual egg protein (primarily ovalbumin) varies by:
  • Manufacturer
  • Production methods
  • Vaccine type
  • Batch/season 2
• Most conventional influenza vaccines contain "limited" or "small" amounts of residual egg protein 1
• Some vaccines have been measured to contain between 0.02-1.2 μg/mL of ovalbumin/ovomucoid 3

Egg-Free and Reduced Egg Content Options

Not all influenza vaccines contain egg protein. According to more recent guidelines:

• Cell-based vaccines (ccIIV4, such as Flucelvax Quadrivalent): Viruses are propagated in mammalian cells rather than eggs, though some starting viruses may be egg-derived. These contain theoretical maximum of 5×10⁻⁸ μg/0.5 mL dose of total egg protein 1

• Recombinant vaccines (RIV3, RIV4, such as Flublok): These are considered completely egg-free as they are produced using recombinant technology 1

Clinical Implications for Egg-Allergic Individuals

The presence of egg protein has historically raised concerns about vaccinating people with egg allergies:

• Older guidelines (pre-2010) were more cautious about administering influenza vaccines to egg-allergic individuals 1

• More recent evidence suggests that even people with egg allergy can safely receive most influenza vaccines:

  • Studies have demonstrated that egg-allergic individuals can safely receive influenza vaccines, even those with severe egg allergy 4
  • Approximately 4,315 patients with egg allergy have safely received 4,872 total doses of trivalent influenza vaccine in clinical studies 4

• For individuals concerned about egg allergy, options include:

  1. Using egg-free recombinant vaccines
  2. Using cell-based vaccines with minimal egg protein
  3. Following appropriate protocols for vaccination of egg-allergic individuals 1

Important Considerations

• Package inserts should be consulted for specific information about egg protein content in different vaccine formulations 1
• Manufacturers may use different compounds to inactivate influenza viruses and may add antibiotics to prevent bacterial contamination 1
• Some influenza vaccines also contain thimerosal as a preservative, particularly in multi-dose vials 1

The egg protein content in influenza vaccines is an important consideration for individuals with egg allergies, but current evidence suggests that most egg-allergic individuals can safely receive influenza vaccination with appropriate precautions or by using egg-free alternatives.