Fluenz nasal vaccine ingredients

Fluenz contains MSG (monosodium glutamate monohydrate) and genetically modified organisms (GMOs).

The active substances are:

Reassortant influenza virus* (live attenuated) of the following three strains**:

A/Missouri/11/2025 (H1N1)pdm09-like strain (A/Switzerland/6849/2025, MEDI 400592) 10 7.0±0.5 FFU***

A/Darwin/1454/2025 (H3N2)-like strain (A/Darwin/1369/2025, MEDI 406666) 10 7.0±0.5 FFU***

B/Tokyo/EIS13-175/2025-like strain (B/Perth/115/2025, MEDI 407730) 10 7.0±0.5 FFU***

..................................................................................................................per 0.2 ml dose

* Propagated in fertilised hens' eggs from healthy chicken flocks.

** Produced in VERO cells by reverse genetic technology. This product contains genetically modified organisms (GMOs).

*** Fluorescent Focus Units.

This vaccine complies with the WHO (World Health Organisation) recommendations (Northern Hemisphere) and EU decision for the 2026/2027 season.

The vaccine may contain traces of the following substances: egg proteins (e.g. ovalbumin) and gentamicin.

The other ingredients are sucrose, dipotassium phosphate, potassium dihydrogen phosphate, gelatin, arginine hydrochloride, monosodium glutamate monohydrate and water for injections.

A pharmacologist's analysis

We asked one of Informing Consent’s medical advisers, a retired pharmacologist, for his thoughts on the ingredients. Here is his analysis:

Excipients (Section 6.1):

Sucrose — stabiliser; trivial quantity, no concern
Dipotassium phosphate — buffer; trace electrolyte, no concern
Potassium dihydrogen phosphate — buffer; trace electrolyte, no concern
Gelatin (porcine, type A) — stabiliser; the main excipient concern. Well-documented cause of rare anaphylaxis and systemic allergic reactions in vaccines, including live-attenuated ones. Contraindicated in known gelatin allergy.‌
Arginine hydrochloride — stabiliser; amino acid salt, no concern at this dose
Monosodium glutamate monohydrate — stabiliser; trace quantity, no evidence of harm via nasal route
Water for injections — solvent; no concern

Trace impurities:

Egg proteins (ovalbumin) — residual from egg propagation; contraindicated in severe egg allergy
Gentamicin — residual from manufacturing; contraindicated in known gentamicin allergy

Key contraindications (per Summary of Product Characteristics – SmPC).

So those who should avoid this product include:

Children with severe allergy to eggs, egg proteins, gentamicin, gelatin, or any ingredient
Immunocompromised individuals
Children receiving salicylates (Reye’s syndrome risk)
Children <2 years

He also says:

‘I can’t comment on the specific strains used with respect to efficacy or safety.

With respect to the route of administration: intranasal administration is generally well-tolerated for this vaccine, and mucosal delivery has some theoretical advantages for local immunity (i.e. IgA antibodies).

In summary:

Fluenz contains no heavy metals, thimerosal, squalene, or human foetal tissue. The principal safety consideration is gelatin, which has a documented – if rare – association with hypersensitivity reactions. Egg and gentamicin traces are also listed as contraindications. The rest of the excipient profile does not appear to present notable concerns.’

Please note: this website is for information only. It is not a replacement for advice from your primary healthcare provider, and it is not legal advice.

Please consult your healthcare provider before making any changes to medication, diet or lifestyle.

The views of the individuals featured on this website are not necessarily the views of Informing Consent. However, we are united in our efforts to protect children's health.

Fluenz nasal vaccine ingredients

A pharmacologist's analysis

Next: Effectiveness of the vaccine

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