Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Influenza and Flu-like Illness article more useful, or one of our other health articles.
Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit https://www.nice.org.uk/covid-19 to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.
Influenza is a major cause of morbidity and mortality each year in the UK. Vaccination has been available since the late 1960s. It is offered annually to patients aged over 65 years, and to all those aged between 6 months and 65 years in clinical at-risk groups identified by the Department of Health (DH).
In the 2018/19 flu season, flu vaccine should also be offered to all children who are aged 2 and 3 years on August 31 2018, as well as all those in primary school reception and years 1-5, in addition to all primary school-aged children in former primary school pilot areas.
The World Health Organization (WHO) monitors influenza viruses throughout the world and recommends which strains are to be included in the current year's vaccine. It is recommended that quadrivalent vaccines (QIVs) for use in the 2018-2019 northern hemisphere influenza season contain the following:
- An A/Michigan/45/2015 (H1N1)pdm09-like virus.
- An A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus.
- An B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage).
- A B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage).
It is recommended that the influenza B virus component of trivalent vaccines for use in the 2018-2019 northern hemisphere influenza season be a B/Colorado/06/2017-like virus of the B/Victoria/2/87-lineage.
In the UK for the 2018-19 season:
The adjuvanted trivalent vaccine (aTIV) should be given to all aged 65 and over. Since aTIV was only licensed for use in the UK in August 2017, this was not an option for the 2017/18 season. However the Joint Committee on Vaccination and Immunisation (JCVI) advice is that this is now the best option for 2018/19 for the 65+ age group. The rationale given by Public Health England (PHE) for this choice is that the adjuvanted vaccine has been shown to be significantly more effective in adults aged 65 and over, with those over 75 benefiting the most.
The quadrivalent vaccine (QIV) should be given to 18- to 65-year-olds at increased clinical risk (including pregnant women). In light of an independent cost-effectiveness study into QIV undertaken by PHE and considered by JCVI, the Green Book was updated in October 2017 to provide the advice that QIV is the best option for 18-65 at-risk groups in the 2018/19 season. It is also used for the childhood programme.
Method of administration
- Vaccines are normally given intramuscularly (IM) into the upper arm or anterolateral thigh.
- The live attenuated influenza vaccine (LAIV), Fluenz Tetra®, is a nasal spray used for children aged 2-18 years.
- If patients have a bleeding disorder (eg, haemophilia), deep subcutaneous injection is appropriate.
- Influenza vaccine can be given with other vaccines, preferably in different limbs. If both vaccines have to be given in the same limb, the sites should be at least 2.5 cm apart.
- The batch numbers and sites of the vaccines should be recorded in the patient's notes.
- If the vaccine is given for employment purposes, the employer should also keep a record.
Influenza vaccine uptake in primary care patients from 1 September 2017 to 31 January 2018 in England was:
72.6% for patients aged 65 years and over, compared to 70.5% in 2016 to 2017.
48.9% for younger patients in one or more clinical at-risk group, compared to 48.6% in 2016 to 2017.
47.2% in all pregnant women, compared to 44.9% in 2016 to 2017.
42.8% for all 2-year-olds, compared to 38.9% in 2016 to 2017.
44.2% for all 3-year-olds, compared to 41.5% in 2016 to 2017.
39.9% for carers, compared to 44.9% in 2016 to 2017.
A considerable regional variation in uptake was observed for patients aged 65 and over, ranging from 66.9% in London to 75.5% in Cheshire and Merseyside. There was also regional variation observed for patients in risk groups, with vaccine uptake ranging from 45.4% in London to 52.4% in Greater Manchester. Vaccination rates for pregnant women ranged from 41.1% in London to 52.1% in Greater Manchester.
The 2017 to 2018 season saw 68.7% of all frontline healthcare workers reported to have received the vaccine in England. This is a significant increase in uptake compared with 63.2% who received the vaccine in the 2016-2017 season.
The effectiveness of influenza vaccine depends upon the composition of the vaccine, the circulating strains, the type of vaccine and the age of the individual being vaccinated.
Apart from 2014/15, the vaccines of recent years have closely matched the influenza A viruses circulating during the season. Studies have suggested an overall effectiveness against confirmed disease of around 59% in adults aged 18-65 years. The lower effectiveness against A(H3N2) from 2016 has been attributed to the vaccine strains acquiring egg adaptive changes.
LAIV has been shown to provide a higher level of protection for children than trivalent inactivated influenza vaccine; a recent meta-analysis suggested an efficacy against confirmed disease of 83%.
Storage, presentation and disposal
- Store at 2-8°C and protect from light.
- Discard if frozen.
- Extremes of temperature can reduce potency. Freezing can cause hairline cracks in the container.
- All vaccines are supplied in the inactive form in pre-filled syringes (or a nasal applicator) which should be shaken before use. Dispose of the vaccination equipment in a sealable, puncture-proof sharps box (UN-approved BN7390).
Types of vaccine
Most of the currently available vaccines are grown in embryonic hens' eggs and then chemically inactivated and purified, but cell-based production is likely to become more important in future years.
There are three types available:
- 'Split virion, inactivated' or 'disrupted virus' vaccines - the whole virus is inactivated by exposing it to organic solvents or detergents.
- 'Surface antigen, inactivated' vaccines - these contain haemagglutinin and neuraminidase antigens prepared from disrupted viruses.
- A live attenuated vaccine - eg, Fluenz Tetra® - which is preferred for children aged 2-18 years because it provides a higher level of protection.
In August 2017 an adjuvanted trivalent inactivated vaccine (aTIV), Fluad®, licensed for use in those aged 65 years and older, gained marketing authorisation in the UK. PHE estimates that, even with conservative estimates of improved effectiveness, the adjuvanted vaccine will be highly cost-effective in both the 65-74 and 75-year and over age groups.
Dosage and schedule
- Immunocompetent adults, including pregnant women, and children aged 13 years and over, should be given a single dose of trivalent vaccine.
- Children not in a clinical risk group only require one dose of the vaccine. The patient information leaflet provided with LAIV states that children should be given two doses of this vaccine if they have not had flu vaccine before. However, JCVI considers that a second dose of the vaccine provides only modest additional protection. On this basis, JCVI has advised that most children should be offered a single dose of LAIV.
- Children in clinical risk groups, aged 2 years or older but under 9 years and who have not received influenza vaccine before, should receive a second dose of vaccine at least four weeks later.
- Vaccinated children should avoid contact with severely immunocompromised individuals for two weeks after vaccination.
Immunocompromised patients (including HIV infection, regardless of CD4 count) should be given influenza vaccine in accordance with the recommendations below. They may not make a full antibody response, so protection may not be as high as for immunocompetent patients. Consideration should also be given to vaccinating household contacts of immunocompromised patients, ie those sharing living accommodation on most days over the winter.
Immunocompromised children, and those living in close contact with those who are immunocompromised, should be offered inactivated vaccine and not live vaccine.
Recommendations for use
People at risk of influenza
The national policy is that influenza vaccine should be offered to the following groups:
- All those aged 65 years and over.
- Residents of nursing or residential homes for the elderly and other long-stay facilities.
- Carers of persons whose welfare may be at risk if the carer falls ill.
- All those aged 6 months or over in a clinical risk group (listed below).
- Health and social care workers.
In 2012, JCVI recommended that the programme should be extended to all children aged 2-16 years. The phased introduction of this extension began in 2013 with the inclusion of children aged 2 and 3 years in the routine programme.
|Clinical risk groups||Examples (decision based on clinical judgement)|
|Chronic respiratory disease|
|Chronic heart disease|
|Chronic liver disease|
|Chronic neurological disease|
All pregnant women should receive the trivalent seasonal influenza vaccine.
The target groups for a one-off pneumococcal vaccination are very similar (see the separate Pneumococcal Vaccination article), so often both are given together in 'flu clinics'.
- Those living in long-stay residential care homes or other long-stay care facilities, where rapid spread is likely to follow introduction of infection and cause high morbidity and mortality (this does not include prisons, young offender institutions, university halls of residence, etc).
- Those who are in receipt of a carer's allowance, or those who are the main carer for an elderly or disabled person whose welfare may be at risk if the carer falls ill. This should be given on an individual basis, at the GP's discretion, in the context of other clinical risk groups in their practice.
GPs should take into account the risk of influenza infection exacerbating any underlying disease that a patient may have, as well as the risk of serious illness from influenza itself. GPs should consider on an individual basis the clinical needs of their patients, including individuals with:
- Multiple sclerosis and related conditions.
- Hereditary and degenerative diseases of the central nervous system.
NB: Individuals working closely with poultry are no longer thought to be high-risk.
Employers - eg, healthcare trusts and nursing and care homes - should offer influenza vaccination to staff directly involved in patient care as an adjunct to good infection control procedures:
- Clinicians, midwives and nurses, paramedics and ambulance drivers.
- Occupational therapists, physiotherapists and radiographers.
- Primary care providers such as GPs, practice nurses and district nurses.
- Staff who look after older people in nursing and care homes.
Vaccination of healthy children
In the 2018/19 flu season, flu vaccine should also be offered to all children who are aged 2-9 years old (but not 10 years or older) on 31 August 2018 and to all primary school-aged children in former primary school pilot areas. This is different from previous years because:
Reception Year children (aged 4-5 years) will now be offered flu vaccination in their reception class, rather than at their general practice surgery.
Children in School Year 5 will be included in the programme this year as part of the phased roll-out of the children's programme.
Contra-indications to all influenza vaccinations
There are few contra-indications. When in doubt, seek the guidance of a local communicable disease consultant, paediatrician or immunisation co-ordinator. Vaccine should not be given to patients with:
- A confirmed anaphylactic reaction to a previous dose of the vaccine.
- A confirmed anaphylactic reaction to any component of the vaccine.
Egg allergy: routine vaccine should not be given where there is a confirmed severe anaphylactic hypersensitivity to egg products, as the vaccines are prepared in hens' eggs. It has now been advised that, except for those with severe anaphylaxis to egg, which has previously required intensive care, children with an egg allergy can be safely vaccinated with Fluenz Tetra®. An egg-free vaccine is available and can be given.
Inactivated influenza vaccines that are egg-free or have a very low ovalbumin content (<0.12 μg/ml) are available and it has been shown that they may be used safely in individuals with egg allergy. Since 2016 the ovalbumin content of LAIV has been reduced to ≤0.12 micrograms/ml. The ovalbumin content of influenza vaccines will be published prior to the influenza season.
A careful history should rule out previous non-life-threatening reactions (eg, rash, or reactions which were not truly anaphylactic). Seek the advice of a specialist when in doubt.
In addition, live attenuated vaccines are contra-indicated for those who:
- Are clinically severely immunodeficient secondary to a condition or immunosuppressive therapy - eg, leukaemias, HIV (not on active antiretroviral therapy - ART) and high-dose corticosteroids.
- Are receiving salicylate therapy.
- Are severely asthmatic (level 4 or above) or actively wheezing at the time of vaccination.
- Intercurrent illness - vaccination may be postponed in the event of an acute illness, but minor illness without pyrexia or systemic upset should not be a reason for delay.
- Premature infants - at-risk premature infants should have vaccination at the appropriate chronological age, preferably with thiomersal-free vaccine.
- HIV infection - immunosuppressed patients should be given the vaccine, irrespective of CD4 count. A full antibody response may not be produced. See above also for Fluenz Tetra®.
NB: side-effects may be more pronounced if both seasonal influenza and swine influenza vaccinations are co-administered.
- Angio-oedema, urticaria, bronchospasm and anaphylaxis can occur. This is an immediate reaction, usually due to hypersensitivity to residual egg protein.
- Neuralgia, paraesthesiae, convulsions and transient thrombocytopenia have been reported rarely.
- Guillain-Barré syndrome has (very rarely) been reported (1-2 cases per million vaccinated people).
- Encephalomyelitis, neuritis (mainly optic) and vasculitis have also (very rarely) been reported but a definite causal relationship with influenza vaccine has not been established.
- All suspected reactions in children and severe suspected reactions in adults should be reported using the Yellow Card Scheme to the Commission on Human Medicines.
NB: the National Institute for Health and Care Excellence (NICE) has stated that zanamivir and oseltamivir can be used for the prevention and treatment of influenza - but are not a substitute for vaccination.
Further reading and references
Flu vaccination: increasing uptake; NICE Guideline (Aug 2018)
Immunizations - seasonal influenza; NICE CKS, May 2018 (UK access only)
Turner PJ, Southern J, Andrews NJ, et al; Safety of live attenuated influenza vaccine in atopic children with egg allergy. J Allergy Clin Immunol. 2015 Aug136(2):376-81. doi: 10.1016/j.jaci.2014.12.1925. Epub 2015 Feb 13.
Influenza: the Green Book, Chapter 19; Public Health England (August 2015)
Seasonal influenza vaccine uptake in GP patients: winter season 2017 to 2018; Final data for 1 September 2017 to 31 January 2018, Public Health England (2018)
Seasonal influenza vaccine uptake in healthcare workers (HCWs) in England - winter season 2017 to 2018; Final data for 1 September 2017 to 28 February 2018, Public Health England (2018)
Rondy M, Larrauri A, Casado I, et al; 2015/16 seasonal vaccine effectiveness against hospitalisation with influenza A(H1N1)pdm09 and B among elderly people in Europe: results from the I-MOVE+ project. Euro Surveill. 2017 Jul 2722(30). pii: 30580. doi: 10.2807/1560-7917.ES.2017.22.30.30580.
Osterholm MT, Kelley NS, Sommer A, et al; Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2012 Jan12(1):36-44. doi: 10.1016/S1473-3099(11)70295-X. Epub 2011 Oct 25.
Influenza vaccine: ovalbumin content; Public Health England, 2018
Fiore AE, Bridges CB, Cox NJ; Seasonal influenza vaccines. Curr Top Microbiol Immunol. 2009333:43-82. doi: 10.1007/978-3-540-92165-3_3.
Online reporting site for the Yellow Card Scheme; Medicines and Healthcare products Regulatory Agency (MHRA)
Amantadine, oseltamivir and zanamivir for the treatment of influenza; NICE Technology Appraisal Guidance, February 2009