What are the recommended dose, administration route, schedule, and contraindications for the MDCK‑cell–derived trivalent subunit influenza vaccine?

MDCK Cell-Derived Trivalent Subunit Influenza Vaccine (Flucelvax)

Dosing and Administration

Flucelvax is administered as a 0.5 mL intramuscular injection for all persons aged ≥6 months, with the deltoid muscle preferred for adults and older children, and the anterolateral thigh for infants and younger children. 1

Age-Specific Dosing

• Children 6-35 months: 0.5 mL per dose 1
• Children ≥36 months through adults: 0.5 mL per dose 1
• Geriatric patients ≥65 years: 0.5 mL per dose (though antibody responses may be lower than in younger adults) 2

Dosing Schedule

• Children 6 months through 8 years: May require 2 doses administered ≥4 weeks apart depending on prior vaccination history 1
• All other age groups: Single annual dose 1

Vaccine Composition

Flucelvax contains 45 mcg total hemagglutinin (HA) per 0.5 mL dose, with 15 mcg HA from each of three influenza strains (two influenza A strains and one influenza B strain). 2 The vaccine is manufactured using Madin-Darby Canine Kidney (MDCK) cells rather than eggs, making it distinct from traditional egg-based vaccines. 1, 2

Key Manufacturing Characteristics

• No egg protein or antibiotics in the formulation 2
• Pre-filled syringes contain no preservative 2
• Multi-dose vials contain thimerosal (25 mcg mercury per 0.5 mL dose) 2
• May contain residual MDCK cell protein (≤21.6 mcg), MDCK cell DNA (≤10 ng), and other process-related substances 2

Contraindications and Precautions

Safety in Special Populations

Pregnancy: The vaccine can be administered during pregnancy, with safety data from 665 pregnancy outcomes showing miscarriage and major birth defect rates (1.9% each) consistent with background rates. 2 Animal studies showed no adverse effects on fertility or fetal development. 2

Lactation: While excretion in human milk is unknown, the developmental benefits of breastfeeding should be weighed against the mother's need for vaccination. 2

Pediatric: Not established for children <6 months of age 2

Geriatric: Safe for use in adults ≥65 years, though antibody responses are lower compared to younger adults 2

Clinical Efficacy

The vaccine demonstrated moderate effectiveness in preventing influenza-related outcomes. In a multinational trial of adults aged 18-49 years, Flucelvax showed efficacy against culture-confirmed symptomatic influenza. 2 Early clinical data from comparative studies showed the MDCK cell-derived vaccine to be equal to conventional egg-derived vaccines in terms of safety and immunogenicity, with 83-100% of recipients achieving hemagglutination inhibition titers >40 post-immunization. 3, 4

Common Pitfalls to Avoid

• Incorrect dose volume: Unlike some other trivalent vaccines (e.g., Afluria, Fluzone), Flucelvax uses 0.5 mL for ALL age groups ≥6 months—do not reduce to 0.25 mL for young children 1
• Underdosing correction: If a smaller dose is inadvertently given to someone ≥36 months, administer the remaining volume immediately or give a full repeat dose 1
• Thimerosal content: Be aware that multi-dose vials contain mercury preservative, which may be a concern for some patients 2