Vaccine Pregnancy: UK SPC 4.6: 'Fluenz is not recommended during pregnancy.' There is a moderate amount of data in pregnant women - no evidence of significant maternal adverse outcomes in 138 pregnant women in a US health insurance claims database, and no unusual patterns of pregnancy complications or foetal outcomes in more than 300 case reports - and animal studies do not indicate reproductive toxicity, but the vaccine is still not recommended in pregnancy. Breast-feeding: limited evidence suggests Fluenz is not excreted in breastmilk, but because data are limited and some viruses are excreted in human milk, 'Fluenz should not be used during breast-feeding'. Fertility: no data exist regarding possible effects on male or female fertility. (Relevance to this page is limited - the product is licensed only from 2 years to under 18 years.)

Influenza vaccine (live attenuated, intranasal)

Brand names: Fluenz Tetra

A live attenuated, cold-adapted influenza vaccine given as a nasal spray, used for seasonal influenza prophylaxis, principally in children as part of the UK childhood immunisation programme.

Adult dose

Dose: Prevention of influenza disease in children and adolescents from 2 years to less than 18 years of age (the whole of this vaccine's licensed population - this SPC carries no adult regimen): 0.2 ml, administered as 0.1 ml in each nostril.

Route: Intranasal - for nasal use only. SPC 4.2: 'Fluenz should under no circumstances be injected.' It is administered as a divided dose in both nostrils: after administering half of the dose in one nostril, administer the other half of the dose in the other nostril immediately or shortly thereafter. The patient can breathe normally while the vaccine is being administered - there is no need to actively inhale or sniff.

Frequency: A single 0.2 ml dose. For children 2 to 8 years of age who have not previously been vaccinated against seasonal influenza, a second dose should be given after an interval of at least 4 weeks. SPC 4.1 adds that Fluenz should be used in accordance with official recommendations.

Section 4.1 verbatim: 'Fluenz is indicated for active immunisation for the prevention of influenza disease in children and adolescents from 2 years to less than 18 years of age. Fluenz should be used in accordance with official recommendations.' That was a mis-set expectation rather than a sourcing gap: this page is the UK childhood-programme live attenuated intranasal vaccine (specialty Paediatrics + Infectious Disease, route Intranasal, brand Fluenz Tetra), and 4.1 now proves the product is licensed for 2 to <18 years only. There is therefore no adult regimen to find, and the figure published above is the label's own paediatric figure, used unchanged - nothing has been scaled, converted or inferred. NOT LICENSED UNDER 2 YEARS - 4.2 verbatim: 'Fluenz should not be used in infants and toddlers below 2 years of age because of safety concerns regarding increased rates of hospitalisation and wheezing in this population.' NO 'ANNUAL' WORDING IN THE LABEL: the word 'annual' does not appear anywhere in this SPC. NO MAXIMUM DOSE IS PRINTED in 4.2, so maxDose is deliberately absent. FURTHER 4.4 CAUTIONS: Fluenz should not be administered to children and adolescents with severe asthma or who are currently wheezing; administration should be postponed in severe acute febrile illness or acute infection, and in nasal blockage (the presence of mild common-cold symptoms without nasal blockage should not result in deferral); syncope has been observed following intranasal administration, so procedures should be in place to prevent injury from fainting. LIVE VACCINE, TRANSMISSION RISK (4.4): recipients should be informed that this is an attenuated live virus vaccine with the potential for transmission to immunocompromised contacts, and should avoid close association with severely immunocompromised individuals (e.g. bone marrow transplant recipients requiring isolation) for 1-2 weeks following vaccination; peak vaccine virus recovery occurred 2-3 days post-vaccination in clinical studies. TRUNCATION: sections 4.1, 4.2, 4.3, 4.4 (including the 4.5 interaction text) and 4.6 are complete in this bundle; 4.8 is cut off at the source-fetch limit part-way through the paediatric paragraph, so the adverse-reaction list below is not the complete 4.8.

Paediatric dose

Dose: 0.2 ml, administered as 0.1 ml in each nostril (children and adolescents from 2 years to less than 18 years of age)

Route: Intranasal - for nasal use only; must never be injected. Given as a divided dose, half into one nostril then half into the other immediately or shortly thereafter.

Frequency: A single 0.2 ml dose. In children 2 to 8 years of age who have not previously been vaccinated against seasonal influenza, a second dose after an interval of at least 4 weeks.

This is a FIXED INTRANASAL VOLUME, not a per-kilogram dose. dosePerKg is deliberately null so that no weight-based calculator can multiply 0.2 by a child's body weight. The figures are the SPC's own paediatric numbers, unscaled. Not to be used below 2 years of age (SPC 4.2). Children and adolescents under 18 years receiving salicylate therapy must not be given this vaccine, and salicylates should not be used in them for 4 weeks after vaccination unless medically indicated.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substances, to any of the excipients listed in section 6.1, or to gentamicin (a possible trace residue)
Severe allergic reaction (e.g. anaphylaxis) to eggs or to egg proteins (e.g. ovalbumin)
Children and adolescents with clinical immunodeficiency due to conditions or immunosuppressive therapy such as acute and chronic leukaemias, lymphoma, symptomatic HIV infection, cellular immune deficiencies, and high-dose corticosteroids. Not contraindicated in asymptomatic HIV infection, nor in those receiving topical/inhaled corticosteroids, low-dose systemic corticosteroids, or corticosteroids as replacement therapy (e.g. for adrenal insufficiency)
Children and adolescents younger than 18 years of age receiving salicylate therapy, because of the association of Reye's syndrome with salicylates and wild-type influenza infection
Not a 4.3 contraindication but a 4.4 precaution: do not administer to children and adolescents with severe asthma or who are currently wheezing, as these individuals have not been adequately studied

Side effects

Very common: nasal congestion/rhinorrhoea (the most common adverse reaction in clinical studies); decreased appetite; malaise
Common: headache; myalgia; pyrexia
Uncommon: hypersensitivity reactions including facial oedema and urticaria; epistaxis; rash
Very rare: anaphylactic reactions
Frequency not known (post-marketing): syncope; Guillain-Barre syndrome; exacerbation of symptoms of Leigh syndrome (mitochondrial encephalomyopathy)
Paediatric safety context (4.8): an increased rate of hospitalisations through 180 days was seen in infants and toddlers 6-11 months of age, and an increased rate of wheezing through 42 days in infants and toddlers 6-23 months of age; neither was increased in recipients 2 years and older, and the vaccine is not indicated below 2 years
This side-effect list may be incomplete — check the full SPC.

Interactions

Salicylates - Fluenz must not be administered to children and adolescents receiving salicylate therapy; salicylates should not be used in children and adolescents for 4 weeks after vaccination unless medically indicated, as Reye's syndrome has been reported following the use of salicylates during wild-type influenza infection
Live attenuated vaccines - can be administered concomitantly with measles, mumps, rubella, varicella and orally-administered poliovirus vaccines
Inactivated vaccines - co-administration with Fluenz has not been studied
Influenza antiviral agents - concurrent use has not been evaluated, but because antivirals may reduce the effectiveness of Fluenz it is recommended not to administer the vaccine until 48 hours after cessation of influenza antiviral therapy; administration of antivirals within two weeks of vaccination may affect the response to the vaccine, and if the two are given concomitantly, revaccination should be considered based on clinical judgement

Clinical monograph

How it works

Contains attenuated influenza virus strains that replicate in the cooler nasopharyngeal mucosa to induce mucosal and systemic immunity without causing influenza disease.

Prescribing in practice

As a live vaccine it is contraindicated in clinically significant immunosuppression and should be avoided where this poses a risk; seek specialist advice for at-risk children.
Strain composition is updated annually to match the strains recommended for the forthcoming season.
Use caution in children with active wheezing or severe asthma, where an inactivated vaccine may be preferred per current immunisation guidance.

Monitoring

No routine laboratory monitoring is required; observe for immediate hypersensitivity after administration.

Counselling the patient

Mild nasal congestion or runny nose, headache and reduced appetite are common and usually short-lived.
The vaccine cannot give you influenza, but full protection takes a couple of weeks to develop.
Tell the clinician about any egg allergy, immune problems or recent unwell contacts before vaccination.

Evidence & guidelines

Recommended within the UK childhood seasonal influenza programme per the Green Book (Immunisation against infectious disease) and UKHSA guidance.

Reference: UK Green Book; JCVI; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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