What is the safest influenza vaccine option for a patient with a known allergy to eggs, considering Flucelvax (influenza vaccine, cell culture-based)?

Flucelvax is an Excellent and Safe Option for Patients with Egg Allergy

Flucelvax (cell culture-based inactivated influenza vaccine) is safe for patients with egg allergy and contains negligible egg protein—a theoretical maximum of only 5×10⁻⁸ μg per 0.5 mL dose, making it essentially egg-free in practical terms. 1

Understanding Flucelvax's Egg Content

• Flucelvax is manufactured using mammalian cell culture rather than embryonated eggs, which fundamentally distinguishes it from traditional egg-based vaccines 1
• While some initial seed viruses may be egg-derived at the start of manufacturing, no eggs are used during the actual production process, and multiple dilution steps result in extraordinarily low theoretical egg protein content 1
• The theoretical maximum egg protein content (5×10⁻⁸ μg/0.5 mL) is several orders of magnitude lower than traditional egg-based vaccines, which contain ≤1 μg/0.5 mL 1
• For comparison, this is approximately 20 million times less egg protein than standard inactivated influenza vaccines 1

Current ACIP Recommendations for Egg-Allergic Patients

Any licensed, age-appropriate influenza vaccine can now be administered to patients with egg allergy, regardless of severity, without special precautions beyond standard vaccination protocols. 2, 3

For Patients with Mild Egg Allergy (Hives Only):

• Administer any age-appropriate influenza vaccine, including Flucelvax, without special precautions 1, 2, 3
• No extended observation period beyond the standard 15 minutes recommended for all vaccines is required 2
• No skin testing is necessary 1
• The vaccine should be given in a setting where personnel and equipment for managing anaphylaxis are available, as with all vaccines 1

For Patients with Severe Egg Allergy (Anaphylaxis, Angioedema, Respiratory Distress):

• Any age-appropriate influenza vaccine can still be used, including Flucelvax 2, 3
• Administer in an inpatient or outpatient medical setting under supervision of a provider who can recognize and manage severe allergic reactions 4
• For adults aged 18-49 years, recombinant influenza vaccine (RIV/Flublok) remains an option as it is completely egg-free 1, 2
• Flucelvax is approved for ages ≥2 years (expanded from ≥4 years), making it an excellent option for children who cannot receive RIV 4

Practical Algorithm for Vaccination

1. Assess egg allergy history:

   • Can the patient eat lightly cooked eggs (e.g., scrambled eggs) without reaction? If yes, proceed with any age-appropriate vaccine per usual protocol 1, 3

2. For confirmed egg allergy:

   • Mild (hives only): Administer any age-appropriate vaccine including Flucelvax; observe 15 minutes 2, 3
   • Severe (anaphylaxis, respiratory symptoms): Administer in medical setting with allergist supervision capability; Flucelvax or RIV preferred but any vaccine acceptable 3, 4

3. Age considerations:

   • Ages 2-17 years: Flucelvax is an excellent choice given its negligible egg content 4
   • Ages 18-49 years: Either Flucelvax or RIV (completely egg-free) 1, 2
   • Ages ≥50 years: Flucelvax or consider high-dose/adjuvanted vaccines if age ≥65 years 5

Evidence Supporting Safety

• A systematic review of 4,172 patients (including 513 with severe egg allergy) found no occurrences of anaphylaxis to influenza vaccines, though some mild reactions occurred 1
• Multiple studies totaling approximately 4,315 patients receiving 4,872 doses (including 656 with severe egg allergy receiving 740 doses) demonstrated that egg-allergic individuals have no increased risk compared to the general population 6
• VAERS surveillance data from 2011-2013 showed no disproportionate reporting of allergic reactions or anaphylaxis following implementation of liberalized egg allergy recommendations 1

Common Pitfalls to Avoid

• Do not unnecessarily delay or withhold influenza vaccination due to egg allergy concerns—this outdated practice deprives high-risk patients of critical protection 2, 6
• Do not perform skin testing with the vaccine—this is no longer recommended and provides no additional safety benefit 1, 2
• Do not use graded dosing protocols (splitting the vaccine into multiple doses)—this is unnecessary with current vaccines 1
• Do not require allergist referral for mild egg allergy—primary care providers can safely administer the vaccine 3
• Ensure all vaccination providers are familiar with office emergency plans and certified in CPR, as with all vaccine administration 1, 3

Key Distinction: Vaccine Allergy vs. Egg Allergy

A history of severe allergic reaction to a previous influenza vaccine itself (not egg) is a contraindication to future receipt of that specific vaccine type. 4 In such cases, consultation with an allergist is warranted to identify the responsible vaccine component, and alternative vaccine formulations should be considered.