Why are we vaccinating children against flu?

With all the additions this year to the childhood immunisation schedule, together with the tougher targets for adult vaccination against seasonal flu, practice nurses may be forgiven for wondering why children have been added to target groups

Practice nurses are familiar with the rational for vaccinating elderly patients, those with specific clinical risks and pregnant women against seasonal flu, and generally accept the advice that they themselves should be immunised to protect both themselves, their families and their patients from infection.

But it may come as a surprise to learn that the incidence of flu in children under the age of 5 years is greater than in the elderly. Children under the age of 2 years are at highest risk of influenza and are most likely to develop serious complications, including pneumonia, secondary bacterial infection and sepsis.¹ Younger children are more likely to need hospital admission than older children, and even among previously healthy children, the death rate for children less than 5 years is high.¹

In a UK-based study, the childhood mortality rate from flu was 6 per million population, with the highest death rates occurring in those aged less than a year, Bangladeshi children (47 per million population) and Pakistani children (36 deaths per million population).²

Not only are the children themselves at risk, but their families are also 'victims' of flu in children: total illness episodes, febrile illness episodes, analgesic use, school absenteeism, parental industrial absenteeism, and secondary illness among family members were significantly higher during the influenza season compared with the non-influenza winter season. For every 100 children followed up for this influenza season, which included 37 school days, an excess 28 illness episodes and 63 missed school days occurred. Similarly, for every 100 children followed up, influenza accounted for an estimated 20 days of work missed by the parents and 22 secondary illness episodes among family members.³ The evidence shows that vaccinating children can protect the individual and contribute significantly to reducing the spread of disease to their families and communities.¹

These are among the factors that persuaded the Joint Committee on Vaccinations and Immunisations (JCVI) to recommend that children from 2 to under 17 years should be included in the seasonal flu programme.⁴

The extended programme is expected to lower the public health impact of flu appreciably, by averting a large number of cases in children, and through lowering flu transmission in the community, indirectly prevent flu in unvaccinated younger children, people in clinical risk groups, and older adults. In turn, this is expected to substantially reduce flu-related illness, GP consultations, hospital admissions and deaths.⁵

As of September this year, routine vaccination should be offered to all children who were aged two and three years old (but not four years or older) on 1 September 2013. In addition, there will be geographical pilots for 4-10 year olds. The programme will be rolled out over a number of seasons to allow Public Health England to identify the most effective way of implementing it. The pilots are designed to assess issues such as workload, uptake and the logistics of delivery in a range of settings before the programme is rolled out nationwide.⁵

Practices have been instructed to invite all eligible children for vaccination, and to ensure uptake is as high as possible in order to maximise the health benefits of the programme.

THE VACCINE

The vaccine selected for this programme is the Live Attenuated Influenza Vaccine (LAIV), (Fluenz®, AstraZeneca), which is administered as a nasal spray. LAIV has been found to be more effective in children than other inactivated flu vaccines, has a good safety profile in children aged 2 years and older, and it has an established history of use. Contrary to the manufacturer's recommendations, the JCVI says that children should be offered a single dose because it is felt that a second dose provides only modest additional protection and therefore the public health benefit would be greater if more children receive a single dose, than if fewer children were given two doses.⁵

The vaccine contains live strains of influenza that have been genetically modified so that they are attenuated, cold-adapted and temperature sensitive. This means they

• Have been weakened (attenuated) so they replicate to provoke a full immune response, but do not cause influenza to develop
• Are able to replicate in the cooler temperature of the nasopharynx but are not able to replicate efficiently in the warmer temperatures of the rest of the body (cold-adapted and temperature-sensitive)

The tolerability and efficacy of LAIV has been studied in nine controlled studies comprising over 28,500 children and adolescents two to 17 years of age, conducted during seven influenza seasons and over 52,500 children and adolescents from post-authorisation safety studies.⁶ Since it was authorized for use in the US in 2003, more than 64 million doses have been given.⁷

LAIV is administered intranasally. It is supplied in an applicator that allows a divided dose to be administered, one spray in each nostril, and although no additional training is considered necessary, AstraZeneca has produced a useful, interactive training module, available at http://www.nasalspraylearning.co.uk.<sup>8http://www.nasalspraylearning.co.uk.⁸

Neither dose needs to be repeated if the patient sneezes or their nose drips following administration, although practice nurses in Northern Ireland, where the vaccine has been used for at risk children, did find that they had to reassure parents that because the vaccine is absorbed very quickly, it was still likely to be effective even if the child had a runny nose.⁵ It isn't necessary for the child to inhale or sniff as the spray is administered — they can continue to breathe normally. However, in a child with a very blocked nose, it may be better to postpone vaccination until their symptoms have improved.⁸

CONTRAINDICATIONS AND PRECAUTIONS

LAIV should not be given to

• Children less than two years of age
• Children or adolescents who are clinically severely immunodeficient as a result of illness or treatment
• Children who are receiving aspirin because of the association of Reye's syndrome with salicylates and wild-type influenza infection
• Children with an egg allergy as traces of ovalbumin (egg protein) may persist in the vaccine as a result of the manufacturing process

There is potential for transmission of live attenuated influenza virus in LAIV to very severely immunocompromised contacts for one or two weeks following vaccination, so if close contact with such patients is likely or unavoidable, an alternative inactivated flu vaccine should be considered.⁵

The vaccine can be given at the same time as other vaccinations, including other live vaccines. In studies, no changes in immune response have been seen when the vaccine was administered with measles, mumps, varicella and polio (oral) live attenuated vaccines.

Immune response to the rubella vaccine was significantly altered, but this is not thought to be clinically relevant as the rubella vaccine is a two-dose course.

As with all vaccines, appropriate medical treatment and supervision should be at hand in case of an anaphylactic reaction; these have been reported infrequently with this vaccine.

STORAGE

LAIV needs to be stored in a fridge (between 2−8°C) and protected from light; it must not be frozen. Before ordering the vaccine, it may be wise to calculate how much fridge space is needed. Each pack of 10 vaccine applicators is 16 cm by 12 cm by 4 cm (length by width by height).

LAIV has been designed to be stored at temperature range of 2-8°C and therefore all precautions should be taken to maintain storage at this temperature.

However, as it is recognised that accidental temperature deviations commonly occur in clinical practice, studies have been carried out to assess the affect of temperature deviations on vaccine potency. Provided it has not been stored out of a fridge for a maximum of 12 hours at a temperature above 25o C, it can still be used. But if it hasn't been used after this 12-hour period, it should be disposed of.⁵

LAIV also has a shorter shelf life than other flu vaccines, and it is therefore important to check the expiry date before use. All of the supplies of LAIV which have been procured to cover the vaccination season (September to mid-December) will have expired by 16 January 2014, so it is important to ensure that children are vaccinated before the Christmas holidays.⁵

This article was developed independently of AstraZeneca UK Ltd, who provided some of the source material, but had no input into its content, which has, however, been reviewed for accuracy and compliance with the ABPI Code of Practice

REFERENCES

1. Usonis V, Anca I, Francis A et al. Central European Vaccination Advisory Group (CEVAG) Guidance Statement on Recommendations for Influenza Vaccination in Children. BMC Infectious Diseases 2010;10:168

2. Sachedina N, Donaldson L. Paediatric Mortality Related to Pandemic Influenza A H1N1 Infection in England: An Observational Population-based Study. Lancet 2010: 376(9755):1846—1852

3. Neuzil KM, Hohlbein C, Zhu Y. Illness Among Schoolchildren During Influenza Season: Effect on School Absenteeism, Parental Absenteeism from Work, and Secondary Illness in Families. Arch Pediatr Adolesc Med. 2002;156:986—991

4. Joint Committee on Vaccination and Immunisation. JCVI position statement on the annual influenza vaccination programme — extension of the programme to children. Available at: https://www.wp.dh.gov.uk/transparency/files/2012/07/JCVI-statement-on-the-annual-influenza-vaccination-programme-25-July-2012.pdf

5. Department of Health, Public Health England. The flu immunisation programme 2013/14 — extension to children. July 2013. Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/225360/Children_s_flu_letter_2013.pdf

6. FLUENZ Summary of Product Characteristics 2012

7. Data on File. MedImmune, LLC. Gaithersburg, MD

8. AstraZeneca

9. World Health Organization Eastern Mediterranean Regional Office, 2001, Letter regarding the use of Judicially Prohibited and Impure Substances in Foodstuff and Drugs, Egypt.