Flublok Quadrivalent (recombinant influenza vaccine, quadrivalent)
Sanofi · Recombinant Influenza Vaccine
What is Flublok Quadrivalent? Flublok Quadrivalent is a recombinant influenza vaccine manufactured by Sanofi. Unlike egg-based flu vaccines, Flublok is produced using recombinant DNA technology and contains 135 mcg HA per 0.5 mL dose — three times the antigen of standard-dose flu vaccines.
About Flublok Quadrivalent
| Brand Name | Flublok Quadrivalent |
| Generic / INN | recombinant influenza vaccine, quadrivalent |
| Drug Class | Recombinant Influenza Vaccine |
| Manufacturer | Sanofi |
| Administration | Intramuscular (IM) injection |
| FDA Approval | 2013 |
FDA-Approved Uses for Flublok Quadrivalent
Indications are based on FDA approval. Your healthcare provider determines appropriate use based on your specific diagnosis, stage, biomarker status, and overall clinical picture.
- Prevention of influenza disease caused by influenza A and B strains covered by the vaccine
- Approved for adults 18 years of age and older
- Particularly considered for patients who cannot receive egg-based influenza vaccines due to severe egg allergy
How Does Flublok Quadrivalent Work?
Flublok Quadrivalent is produced using a baculovirus expression system — it contains recombinant hemagglutinin (HA) proteins from four influenza strains, with no egg proteins, preservatives, or antibiotics in the formulation. The higher antigen content (135 mcg HA total vs 45 mcg in standard-dose vaccines) is designed to elicit a stronger immune response.
Dosage & Administration
0.5 mL intramuscular injection, once per flu season. For adults 18 years and older. The treating clinician or pharmacist determines the appropriate timing and indication based on current CDC and ACIP recommendations.
Dosing is individualized by the prescribing clinician. Never adjust your dose without consulting your healthcare provider. This information is educational only and does not replace the official prescribing information.
Warnings, Precautions & Side Effects
General Warning
Syncope (fainting) may occur following vaccination. Guillain-Barré syndrome risk should be considered for patients with prior history. Allergic reactions including anaphylaxis are possible. Immunocompromised patients may have a diminished immune response.
- Anaphylaxis / severe allergic reaction
- Syncope post-injection
- Guillain-Barré syndrome (rare association with influenza vaccines)
Common Side Effects
- Injection site pain
- Headache
- Fatigue
- Myalgia (muscle ache)
- Arthralgia
- Injection site erythema
This is not a complete list. Always report new or worsening symptoms to your healthcare provider promptly.
Storage & Handling
Refrigerate at 2°C to 8°C (36°F to 46°F). Do not freeze. Protect from light. Use by expiration date.
BiologicHealthPlus provides temperature-monitored cold-chain specialty delivery for medications requiring refrigeration. Never use a medication if its storage conditions have been compromised.
Insurance Coverage, Prior Authorization & Patient Assistance
🛡️ Commercial Insurance
Flublok Quadrivalent is covered by most major commercial insurance plans when medically necessary and prior authorized. Coverage tier and cost-sharing vary by plan.
✅ Prior Authorization
Prior authorization is required by virtually all insurance plans for Flublok Quadrivalent. BiologicHealthPlus handles the complete prior authorization process at no cost to patients or providers.
🏥 Medicare Coverage
Medicare Part D covers this oral specialty medication. Medicaid coverage varies by state.
🆓 Patient Assistance
Manufacturer patient assistance programs may be available for eligible uninsured or underinsured patients. Contact BiologicHealthPlus for a confidential eligibility review.
Prior Authorization Patient Assistance Insurance & Savings Medication Costs
Frequently Asked Questions — Flublok Quadrivalent
Flublok Quadrivalent is a recombinant influenza vaccine by Sanofi. Unlike conventional egg-grown flu vaccines, it is made using recombinant DNA technology and contains no egg proteins. It delivers 135 mcg of hemagglutinin (HA) per dose — three times the antigen of standard-dose flu vaccines.
Flublok Quadrivalent is approved for adults 18 years and older. It is often recommended for patients with severe egg allergies, those who need a higher-antigen influenza vaccine, and immunocompromised patients per clinician guidance.
Because Flublok is produced using a baculovirus expression system with no egg proteins in the manufacturing process, it is generally considered appropriate for patients with egg allergy of any severity. Consult your healthcare provider.
Influenza vaccines are typically covered under Medicare Part B and most commercial insurance plans as a preventive benefit, often with no cost-sharing when in-network. Coverage for Flublok specifically (vs. standard-dose options) may depend on the plan.
Both are higher-antigen influenza vaccines for adults. Flublok uses recombinant technology (no eggs, 135 mcg HA total). Fluzone High-Dose uses an egg-based manufacturing process but contains 180 mcg HA total and is specifically indicated for adults 65+. Your provider will determine which is appropriate.
Related Medications & Conditions
Related Medications
Fluzone High-Dose Quadrivalent · Fluarix Quadrivalent · FluBlok (prior formulation)
Related Conditions
Influenza prevention · Immunocompromised patients · Egg allergy and influenza vaccination