Can Uptake of Childhood Influenza Immunisation Through Schools be Increased Through Behavioural-insight Informed Changes to the Invitation Process?
Phase: NA
Conditions: Influenza, Human
Sponsor: Public Health England

 
Childhood influenza immunisation invitation trial in schools V1.0 29/06/16 
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Trial Protocol: 
Can uptake of childhood influenza immunisation through schools be 
increased through behavioural-insight informed changes to the 
invitation process? 
 
 
Short title: Childhood influenza immunisation invitation trial in schools 
 
Protocol Version: 1.1 Data: 05/07/2016 
 
Trial Number: TBC 
 
 
 
 

 
Childhood influenza immunisation invitation trial in schools V1.0 29/06/16 
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Investigators 
 
Investigator 
Role 
Organisation 
Dr Tim 
Chadborn (CI) 
Behavioural Insights Lead Researcher, PHE 
Behavioural Insights Team 
PHE 
Dr Rebecca 
Howell-Jones 
Public Health Specialty Registrar, PHE 
Behavioural Insights Team. 
PHE 
Karen Tan 
Behavioural Insights Researcher, PHE Behavioural 
Insights Team 
PHE 
Dr Amanda 
Bunten 
Behavioural Insights Research Analyst, PHE 
Behavioural Insights Team 
PHE 
Pauline 
MacDonald 
Programme Director, National Child Flu 
Immunisation Taskforce (Public Health 
Commissioning Central Team), Medical Directorate 
NHS England 
Sarah Jones 
Childhood Flu Immunisation Taskforce Programme 
Manager (Public Health Commissioning Central 
Team), Medical Directorate 
NHS England 
Angela 
Edwards 
Seasonal Flu Lead /Immunisation Implementation 
& Planning, National Infection Service 
PHE 
Louise Letley 
Nurse Manager (Research), Immunisation 
Implementation & Planning, Immunisation 
Operations, Immunisation, Hepatitis & Blood 
Safety Dept. 
PHE 
Dr Ayoub Saei 
Senior Statistician, Statistics Unit, National 
Infection Service 
PHE 
 
 
 

 
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1. Background 
In 2012, the Joint Committee on Vaccination and Immunisation (JCVI) recommended 
a national childhood influenza immunisation programme be rolled out to 2-16 year 
olds, using a live attenuated influenza vaccine (LAIV) (JCVI, 2012).1 Roll out of the 
programme began in 2013 (winter season 2013/14) with immunisation of 2 and 3 year 
olds through primary care. The following year, 4 year olds were added to this group 
and in 2015/16 the programme was extended to children in school years 1 and 2 
(Table 1). This year (2016/17), all children aged 2-4y and those in years 1 and 2 will 
continue to be offered flu vaccination and the offer is being extended to all those in 
year 3. In a number of geographical areas, pilot programmes were established which 
included a wider age-cohort. The exact cohorts and number of areas participating in 
the pilot studies varied slightly from year to year (Table 1).    
In 2015/16 nationally, uptake in Years 1 and 2 was 53.6%.2 Areas that participated in 
the pilot programme vaccinating primary school children (5-11 years) showed both 
decreasing uptake with increasing age (from 62.6% in Year 1 to 54.7% in Year 6 in 
2015/16) and lower uptake last year than the previous year (57.9% compared with 
60.4%). Delivery methods (school, GP or pharmacy) had considerable impact on 
uptake, with higher uptake in those areas that delivered flu immunisation through 
schoolsi. Analysis has also shown that lower uptake is associated with deprivation and 
ethnicity.  
The majority of areas offer the immunisation through school-based programmes 
delivered by providers that are commissioned by the NHS. Parents of eligible children 
are sent a letter informing them about the vaccination programme and inviting them to 
return the consent form for their child’s vaccination. While uptake in schools is higher 
than GP or pharmacies, there remains approximately 30% of children for who consent 
is neither given nor actively withheld.3  
PHE provides template letters that immunisation providers can use. The PHE 
Behavioural Insights Team has worked with the NHS England and the PHE 
immunisation team to design the template letter for 2016/17. This letter is informed by 
behavioural insight theory to encourage parents to return the consent form.  
There is evidence from the field of behavioural science to suggest that a low cost 
intervention, such as the content of an invitation letter or a reminder text message, 
may be effective in changing behaviour. In a previous trial run by our team, PHE 
Behavioural Insights Team, a 4% increase in health checks was shown by simplifying 
invitation letters and adding a tear-off slip where individuals could note the time and 
                                                          
i (55.6%, 32.9% and 16.1% uptake school, GP and pharmacy delivery respectively) 

 
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date of their first appointment, as a memory aid.4 Redesigning the invitation letter in 
combination with primer and reminder text messages increased uptake by 12% 
compared to the standard letter. Similar effects have been found in other non-health 
areas, for example, research from the Behavioural Insights Team and the DVLA 
showed that including an image of a person’s car in their car tax collection letter 
increased tax payments from 40%-49%5 and an HMRC trial showed that providing a 
localised social norm message increased tax returns by 5%.6  
Here we set out our proposal to test whether behaviourally-informed interventions (i.e. 
the new template letter and SMS/email reminders) increase uptake of childhood 
influenza vaccination in schools, through increasing response rate. Such evidence 
would encourage adoption of the national template letter, which we understand many 
areas do not currently adopt, provide evidence for the provision of reminders and 
confirm whether the theory-based changes to the invitation letters have the anticipated 
impact.  
Table 1. Target age groups for national and pilot childhood influenza immunisation 
programmes, by winter season. 
Winter 
season 
National programmea 
Pilot programmea 
2013/14 
2y and 3y olds (in primary 
care) 
4-11 year olds (reception to school year 
6) eligible for vaccination in 7 
geographically discrete areas.  
2014/15 
2-4 years of age (in 
primary care) 
Both primary school aged children (5-
11y) and secondary school aged 
children, 11-13y (school years 7 and 8 
age) eligible for vaccination in 14 pilot 
areas (including pilot areas that 
participated in 2013/14)  
2015/16 
2-4 years of age (in 
primary care) and school 
years one and two (5y and 
6y at 31st August) 
6 pilot areas that had piloted the school 
based programme since 2013 to 2014 
continued to offer the vaccine to all 
primary school age children aged 5-11 
years (school years 1 to 6 age). 
2016/17 
2-4 years of age (in 
primary care) and School 
years 1, 2 and 3 (5, 6 and 
7y at 31st August) 
As in 2015/16 primary school children 
in years 1 to 6 in former school pilot 
areas will continue to be offered the 
vaccine.  
a Ages refer to age on 31st August/1st September of the year 

 
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2. Aims and hypothesis  
The aim of this study is to investigate whether behavioural insight-informed changes to 
the invitation process can improve uptake of childhood flu immunisation. Our specific 
hypotheses are:  
1. Changes to the invitation letter will increase return of consent forms and thereby 
increase uptake of childhood flu vaccine through schools. 
2. Reminders to return the consent form will increase return of consent forms and 
thereby increase uptake of childhood flu vaccine through schools 
 
3. Trial design  
3.1. Design overview 
This is a 2x2 factorial design, open-label, randomised (at school level) trial of invitation 
letters and SMS/email reminders for childhood flu immunisation (Figure 1).  
 
 
3.2. Primary and Secondary outcomes 
The primary outcome for this study is the proportion of children in school years 1-3 
who receive influenza immunisation as part of the national childhood immunisation 
programme.  
We will also look at a number of secondary outcomes to determine the effect of the 
interventions on influenza immunisation in different age groups and on consent-giving. 
The secondary outcomes are: 
Figure 1. Randomisation and trial arms 

 
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1) Proportion of children who receive influenza immunisation 
a) in school years 4-6ii 
b) in Receptioniii  
c) in each individual year group 
2) Proportion of children for who consent is neither given nor withheld (i.e. non-
responders) 
a) in school years 1-3 
b) in school years 4-6 
c) in each individual year group 
3.3. Intervention and control 
There are four arms to this 2x2 study: 
1. New template invitation letter and SMS/email reminder 
2. New template invitation letter and no reminder 
3. Last year’s invitation (control) letter and SMS/email reminder 
4. Last year’s invitation (control) letter and no reminder 
Parents at schools randomised to one of the new template letter intervention arms will 
receive the behavioural-insight informed invitation letter (Appendix 1), with minimal 
local adjustments. The behavioural-insight framing for this letter are summarised in 
Parents at schools randomised to one of the control letter arms will receive the letter 
used by the immunisation provider last year (with necessary updates). These letters 
vary from area to area and examples are given in Appendix 2. 
Schools randomised to one of the reminder SMS/email arms will be asked to send a 
reminder message to parents through their usual email/SMS system (e.g. parentmail). 
Schools will be asked to send a specific message and for this to be sent at a specified 
time ( 
 
                                                          
ii Children in School Years 4-6 (age 8-11y) are included in the immunisation programme in pilot areas including 
Leicestershire and Lincolnshire Area Team and Essex Area Team 
iii Reception children (age 4-5y) are being offered immunisation through schools in Essex Area Team.  

 
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Table 3). These messages are informed by behavioural insights and are action-
orientated with a focus on scarcity in both message (ensure your child doesn’t miss 
out and There will be only one vaccination session at the school). The email message (with 
more space) includes other behavioural science informed messages used in the 
invitation letter. Providers will be given a Standard Operating Procedure detailing how 
this request to schools is to be made and monitored.  
Table 2. 
Parents at schools randomised to one of the control letter arms will receive the letter 
used by the immunisation provider last year (with necessary updates). These letters 
vary from area to area and examples are given in Appendix 2. 
Schools randomised to one of the reminder SMS/email arms will be asked to send a 
reminder message to parents through their usual email/SMS system (e.g. parentmail). 
Schools will be asked to send a specific message and for this to be sent at a specified 
time ( 
 

 
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Table 3). These messages are informed by behavioural insights and are action-
orientated with a focus on scarcity in both message (ensure your child doesn’t miss 
out and There will be only one vaccination session at the school). The email message (with 
more space) includes other behavioural science informed messages used in the 
invitation letter. Providers will be given a Standard Operating Procedure detailing how 
this request to schools is to be made and monitored.  
Table 2. Behavioural insights informed changes to the flu invitation letter and 
rationale. 
Formatting and phrasing used in new 
template invitation letter 
Behavioural rationale 
Formatting 
Reduced in length and made simpler. 
 
Reduces the cognitive effort required 
to process the information and identify 
the action required.  
We have formatted text to highlight the 
key points of note/ actions required. 
Reduces cognitive effort to identify 
action required. 
Provider letterhead plus NHS logo 
NHS is a trusted brand when it comes 
to medical/ health issues. 
Phrasing 
Your child’s annual flu vaccination is 
now due 
Salience of message 
This vaccination programme is in place to 
help protect your child against flu. 
Gain-framed message for prevention 
Flu can be an unpleasant illness and 
sometimes causes serious complications.   
Loss framed message 
Please complete the enclosed consent 
form (one for each child) and return to the 
school [by/ within] [INSERT DATE or 
TIME FRAME] 
Action orientated 
The vaccination is free … 
There is anecdotal evidence that 
parents do not realise it is free or 
annual. Note: the evidence on use of 
‘free’ is mixed as this can be deemed 
as less valuable, particularly by some 
cultures 
… and will be given by a quick and simple 
spray up the nose 
Addresses parental concerns of what 
the vaccination entails 
Last year, most children offered the 
vaccine in schools had the immunisation.  
Social norms 
  
 
 

 
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Table 3. Proposed text for SMS and email reminder message 
Reminder 
format 
Message 
Timing 
SMS (160 
characters 
limit) 
Thank you for returning your child’s flu vaccine 
consent form. If you have not, please return it by 
xxxxxx to ensure your child doesn’t miss out. 
Message to be 
sent two days 
ahead of deadline 
for returning forms  
Email 
Subject: Flu vaccine consent form due xx/xx/xx: make 
sure your child doesn’t miss out  
Dear Parent/Guardian, 
Please return your child’s flu vaccine consent form by 
[insert day and date] to make sure your child doesn’t 
miss out. Thank you to those parents who have 
already done so.  
There will be only one vaccination session at the 
school. Last year, most children offered the vaccine in 
schools had the immunisation.  
[The consent form is attached for use if you have lost 
the letter]a 
If you decide you do not want to vaccinate your child 
against flu, please return the consent form giving the 
reason. This will help us plan and improve the service 
Yours sincerely, 
SIGNED BY PROVIDER 
Message to be 
sent two days 
ahead of deadline 
for returning forms 
aThis sentence will only be included if feasible to include the original letter as an 
attachment 
3.4. Setting 
This trial will be conducted in state schools in participating areas in England. The trial 
will be implemented by the immunisation providers for the areas and schools 
themselves will not be aware that they are taking part in a research study.  
3.5. Trial Sites 
We are working with providers of childhood flu school vaccination in Wessex, Leicester 
and Essex NHS England Area Teams. We will randomise schools in each of the trial 
local authority to one of the four trial arms. Details of the areas and providers which we 
are working with are given in Table 4.  
 

 
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Table 4. Number of schools by area, provider and target cohort. 
Local 
Area 
Team 
Provider 
Local authority 
Years 
in prog 
Number of schools 
Total*  
Infant  
Junior 
Primary 
Special 
Leices
ter 
Leicestershir
e Partnership 
NHS Trust 
Leicester 
Y1-Y6 
91 
9 
9 
66 
7 
Rutland 
Y1-Y6 
19 
0 
0 
17 
2 
Leicestershire 
Y1-Y6 
241 
6 
6 
214 
10 
Essex 
South Essex 
Partnership 
University 
NHS FT  
Essex 
R-Y6 
473 
51 
48 
356 
16 
Southend on 
Sea 
R-Y6 
37 
5 
5 
25 
2 
Thurrock 
R-Y6 
41 
0 
0 
40 
1 
Wess
ex 
Southern 
Healthcare 
Partnership 
NHS Trust 
Hampshire 
Y1-Y3 
454 
117 
104 
207 
26 
Solent NHS 
Trust 
Portsmouth 
Y1-Y3 
53 
16 
12 
23 
2 
Southampton 
Y1-Y3 
59 
10 
8 
37 
4 
Dorset 
Healthcare 
Uni Trust 
Dorset 
Y1-Y3 
150 
4 
4 
124 
8 
Poole 
Y1-Y3 
34 
8 
6 
16 
3 
Bournemouth 
Y1-Y3 
32 
2 
3 
26 
1 
Boots UK 
Isle of Wight 
Y1-Y3 
42 
0 
0 
40 
2 
Total 
 
 
 
1726 
228 
205 
1191 
84 
*Independent schools are excluded. Data are taken from https://www.compare-school-
performance.service.gov.uk/download-data  
3.6. Recruitment 
Three areas and six providers have agreed to take part in this trial. All schools in their 
areas will be included in the trial. Due to the nature of the trial and research question, 
this study will not recruit individual children or individual schools. 
3.7. Power calculations 
Given that all school-based flu immunisation programmes send invitation letters to 
parents, even a small increase in uptake from changes to the phrasing of the letter will 
be worthwhile. Furthermore, given that participating areas will be sending letters to all 
parents of eligible children it is simpler to include all schools within a participating local 
authority area. Including a number of providers, which cover 13 local authorities, 
increases the generalisability of our research findings. We are therefore starting from 
the position of having potentially ~1700 schools to include in the trial. Sample size 
calculations are not therefore appropriate as we are not sampling from the 
participating areas, but rather including the full population. We can however explore 
the potential power of our study. 
Although our allocation will be stratified by local-authority, to explore the potential 
power of the study we have made the crude assumption that all strata are equal (i.e. 
that there is no variation between local authorities). We therefore used sampsi 

 
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followed by the sampclus commands in Stata to estimate our study power. We 
determined the number of schools using data on schools by local authority available 
from Compare school and college performance websiteiv. We used 2015/16 data 
provided for Leicester, Leicestershire and Rutland to estimate the average size of 
each cluster (i.e. average number of children in school years 1-3) (excluding schools 
with fewer than 20 pupils in years 1-3). The average size of cohort was 110, and we 
have therefore conservatively used 100 as our estimate. We used an average vaccine 
uptake of 63.0% (SD 16.2%) in our power calculations.  
We do not have a known value for the intra-class correlation (ICC). Shackleton et al7 
estimated that ICC values for health outcomes in adolescent children ranged from 
ICCs ranged from 0.01 to 0.21 depending on the outcome being measured and the 
country. Within Britain, ICC ranged from 0.01 to 0.15 depending on health outcome, 
with the highest correlation for regular smoking. These health outcomes are not 
directly comparable with vaccine uptake or primary school age children (for which the 
behaviour is actually one of the parents) but nonetheless provide an anchor point 
around which to explore in the absence of more relevant estimates. We used 0.025 as 
our basic estimate.  
We have conducted power calculations that indicate with this number of schools we 
would have 90% power to detect a 1% absolute increase in uptake, from 63% to 64% 
in children in years 1-3. The large number of schools available to us (~1700 schools), 
will enable us to have 90% power to detect an absolute change even if ICC is 
relatively high ( 
 
                                                          
iv Available at https://www.compare-school-performance.service.gov.uk/download-data 

 
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Table 5). Furthermore, we will have the power to detect our secondary outcomes e.g. 
uptake by year group.  
It is possible, due to delays getting this project off the ground, that providers areas will 
need to go ahead with printing their letters before we have the approvals necessary to 
issue the randomisation. Our power calculations show that despite this we are likely to 
have sufficient schools to detect, with 90% power an absolute increase of 2% in 
uptake, with all but the highest estimates of ICC with just one or two providers (e.g 
South Essex NHS Partnership Trust, who have indicated a slightly later date for 
printing letters, has 451 schools. Clearly the size of the effect we have the power to 
detect will also depend on the impact of variation between strata in the trial (which are 
not accounted for in these power calculations).  
 
 

 
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Table 5. Power calculations for various scenarios, assuming no variation 
between strata. 
Outcome 
Scenario 
Absolute 
% change 
able to 
detect 
Power 
ICC 
Number 
clusters 
required in 
each arm 
Total 
number of 
schools 
required 
Primary 
outcome 
Detecting lowest 
absolute effect 
1% 
90% 
0.025 
187 
748 
Primary 
outcome  
Estimate of impact 
of ICC estimates on 
required minimum 
sample size 
2% 
90% 
0.025 
47 
188 
2% 
90% 
0.05 
81 
324 
2% 
90% 
0.15 
214 
856 
2% 
90% 
0.25 
347 
1388 
Secondary 
outcome 
Analysis by 
individual year group 
(i.e. average size of 
the cluster 30) 
2% 
90% 
0.025 
78 
312 
2% 
90% 
0.05 
110 
440 
2% 
90% 
0.15 
240 
960 
2% 
90% 
0.25 
370 
1480 
 
3.8. Randomisation 
Randomisation will be undertaken by PHE Behavioural Insights Team. An up-to-date 
list of schools will be obtained from each area (or obtained from PHE and validated by 
the local team). Schools will be identified by their Unique Reference Number (School 
URN) to create the allocation list. Randomisation will be stratified by Provider and local 
authority. It is unlikely that we will know in advance (i.e. at the time of randomisation) 
which schools have email/SMS systems. (We anticipate this to be fairly common 
amongst schools.) We will therefore allocate all schools, irrespective of their available 
system, to one of the four trial arms. Randomisation will be carried out using a 
randomisation tool (e.g. ralloc or random number generator with schools ranked for 
allocation by random number order) in Stata, or other appropriate statistical-package 
to one of the four arms of the trial.  
3.9. Data collection 
Data are collected by immunisation providers as part of the routine programme. While 
data on the number of vaccines administered and denominators (i.e. not including data 
on consent) will be submitted centrally at the end of November 2016, December 2016, 
January 2017 and February 2017 only the final data submission in March 2017 will 
provide school-level data and data on consent as well as uptake.   
Many areas use a spreadsheet generated by PHE which records individual level data 
for local management and enables data to be cumulated to the different levels 
required (e.g. school, local authority) and includes data on consent. These different 

 
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cumulative levels can be submitted as required, without the inclusion of individual-level 
data.  
School-level data by school year are routinely submitted to PHE. We will obtain final 
school-level data from PHE at the national level in March 2017. These data will then 
be linked with the allocation list for analysis using the School Unique Reference 
(Figure 2). We will ask providers to submit an interim school-level data extract (e.g. in 
November) to enable the analysis to be fully planned (i.e. statistical analysis code 
written) ahead of the availability of final data. This will be important to enable the timely 
production of results which can then inform next year’s programme, however it will not 
be compulsory if an area is not able to provide these interim data. This analysis will be 
seen only by a quorum of the investigators and they will not be results released to the 
wider study team or beyond so as not to impact on the final uptake data. No individual-
level data or Personal Identifiable Information will be collected.  
Data on characteristics of the schools will be obtained from publically available 
sources and linked to the immunisation database. This will include data from gov.uk, 
Compare school and college performance websitev on characteristics such as the 
proportion of children on free school meals, pupils with English not as the first 
language, religious denomination of the school and type of school.  The postcode of 
schools will be linked to Index of Multiple Deprivation (IMD) data to obtain a 
deprivation indicator, quintile or decile ranking, for the school location.  
Providers will obtain data on the implementation and fidelity of any reminder message 
delivered by the school (in line with the Standard Operating Procedure). For schools in 
trial arms 1 and 3 (who will be asked to send reminder messages to parents) providers 
will ascertain whether schools implemented the request to send a message to parents 
and if so, what medium they used (SMS and/or email) and whether they altered the 
message. For schools in trial arms 2 and 4 (who will not be explicitly asked to contact 
parents) providers will ascertain whether schools sent a message to parents (before or 
after the invitation letter but not including mention in newsletters or similar). We 
anticipate that providers will collect this information during the immunisation session at 
the school.  
Finally, given the geographical and temporal variation in immunisation flu uptake levels 
and variation in the use of template letters in different areas, we will collect and 
analyse the letters sent in non-trial areas. This will give us valuable insight into the 
extent to which national templates are adopted and an understanding of the variation 
in invitation letters. This information will inform the understanding of the analysis of the 
trial, with respect to understanding changes in uptake seen from year to year in non-
                                                          
v Available at https://www.compare-school-performance.service.gov.uk/download-data 

 
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trial areas. To collect this information we will request that areas send us a copy of their 
invitation letter for this year’s immunisation programme. This request will most likely be 
sent from NHS England central team (Pauline MacDonald and Sarah Jones – co-
investigators on this trial) asking commissioners to obtain invitation letters from their 
local providers).  
 
Figure 2. Data flow from allocation list, PHE National Infection Service 
immunisation data and school characteristics data, with linkage through the 
School Unique Reference Number (URN). 
 
Abbreviations: NIS: National Infection Service; Pn Provider 
3.10. Data analysis 
Analysis will be undertaken by the PHE Behavioural Insights Team working with the 
Statistic Unit, PHE National Infection Service. Our main analysis will be by intention to 
treat allocation for the primary and secondary outcomes. We will use logistic 
regression to investigate the main effect of the interventions and their interaction. The 
model also will include provider, local authority and school effect to take into account 
extra variation that was not explained by intervention and other confounder variables. 
In the models, we will also investigate the impact of secondary factors such as school-
year (to determine if there’s any greater impact for those that have not previously 

 
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received an invitation letter) and inequalities (e.g. IMD quintile, proportion of children 
eligible for free school meals, proportion of children not with English as first language).  
We will also undertake a per-protocol analysis of the primary and secondary 
outcomes, including in the analysis only those schools in trial arms 1 and 3 who 
implemented the request to send a reminder message with high fidelity to the request 
and those schools in trial arms 2 and 4 who did not send a reminder request. While the 
intention to treat analysis will be a composite of the effectiveness of reminders and the 
prevalence of SMS/email systems, the per-protocol analysis will enable these 
components to be disentangled. 
We will analyse the invitation letters used in non-trials areas by coding the letters using 
the Theoretical Domains Framework (TDF). This will enable us to assess their 
behavioural-insight framing and fidelity to the new template letter. We will analyse 
whether those areas that used a letter similar to the new template had i) higher uptake 
and ii) greater change in uptake from to last year, compared to areas that used a 
dissimilar letter. 
 
4. Study sponsorship and approvals 
This study has been reviewed by the PHE Research Ethics and Governance Group to 
gain approval for PHE to act as the study sponsor.  
Health Research Authority (HRA) approval has been sought, which includes ethical 
(opinion provided through UK Health Departments’ Research Ethics Service), 
governance and legal review. (HRA/ethics number xxxxxxx). 
The trial has been registered on clinicaltrials.gov, trial number xxx.  
 
5. Main risks and mitigation 
5.1. Timelines 
The main risk to the successful implementation of this trial is meeting the timeline to 
enable local areas to implement the randomisation of letters component of the trial 
(mid-July deadline for most areas). The delay in initiating this development of the trial 
has been due to changes in budgets at PHE which led to a reduction and delay in the 
resources that could be allocated to this project. Should the trial not gain approvals in 
time to implement the randomisation of letters in a participating area, we will 
recommend that the area use the behaviour insights informed template letter for all 

 
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schools. Such areas would be invited to trial the effect of the SMS/email reminder on 
uptake. In the unlikely scenario of all areas being unable to participate in the letter-
intervention (due to print-deadlines being ahead of approvals), the evaluation of the 
new template will rely on the ecological-analysis of fidelity to the new template letter in 
non-trial areas and uptake. While we are and will actively work with research sites to 
aim for this approach, if particular areas are unhappy to universally use the new 
template letter, we will take the above approach using the local letter updated from last 
year. One of the main reasons for including a large number of research sites at this 
stage is to give us the greatest possibility of running an effective and sufficiently 
powered trial, given the practical considerations. 
5.2. Ethical issues  
This study is using an intervention letter which is the nationally-available template for 
the childhood schools immunisation programme in the 2016/17 winter season, and by 
contrast using for the control arm, last year’s letters. This potentially raises ethical 
issues given that we expect the intervention letter (which is in fact the national 
template) to be more effective than the control letters used last year. In conducting a 
trial of the letter we are randomising half of the children in participating areas to 
receive last year’s letter. However, there is no direct evidence that the new letter will 
be more effective and, crucially, we need to ensure that there is no unintentional 
decrease in vaccination uptake. 
Furthermore, we understand that there is often reluctance at a local level to change 
letters substantially from one year to the next, even given changes to the national 
template. A randomised trial of the new letter is the best way to obtain evidence as to 
whether the new letter increases uptake of vaccination. If successful, this evidence 
could help argue for increased fidelity to the national template by local programmes 
who would otherwise not change their letter.  
5.3. Consent 
In this trial of invitation letters it is neither desirable nor appropriate to obtain consent 
from schools or individuals to participate. Doing so would invalidate the validity of the 
trial and mean that the research questions cannot be answered. This potentially raises 
ethical concerns but these are mitigated by: 
• the minimal harms that could arise through receipt of different letters or 
SMS/email reminders (there are no invasive or pharmaceutical procedures 
being tested in this research) 
• we will not deviate from current policy or implementation – the vaccine will be 
offered to all children through a uniform approach and schools will not 
experience any difference from last year 

 
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• the population benefit of having robust evidence to answer the research 
question 
• the individual benefit arising from vaccination and the minimal risks – and the 
fact that parents are provided with full information in all arms of the trial and 
have to provide consent to participate in the vaccination programme. 
The providers and commissioners of the childhood flu immunisation programmes in 
participating areas have agreed willingly to take part in the study. The invitation letters 
are signed by the provider and not from the school.  
5.4. Data security 
Routine systems for data collection will be used, with data obtained at school level. 
PHE is the data owner of these information systems. The research team will not have 
access to any patient identifiable information. As the analysts work for PHE, no data 
will leave PHE and the research team will maintain data confidentiality of this 
information, including storage on restricted access PHE drives. School level data are 
not currently made publically available and the research team will adhere to this such 
that no school is identifiable in any published reports. 
 
6. Timeline 
Ethics approval  
Early July 2016 
Randomisation of schools 
Mid July 2016 
Trial implemented (i.e. school letters printed) 
Mid July 2016 
Invitations sent to schools and on to parents 
October to December 2016 
Schools requested to send reminders 
October to December 2016 
Data collection  
Nov 2016, Dec 2016, Jan 2017, Feb 
2017 and final data (with ability to 
adjust denominators) March 2017 
Preliminary data analysis 
Nov/Dec 2016 
Final Analysis/Reporting 
April/May 2017 
 
 
 
 

 
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7. References 
 
                                                          
1 Joint Committee on Vaccination and Immunisation.  JCVI statement on the annual 
influenza vaccination programme – extension of the programme to children.  25 July 
2012. 
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/22477
5/JCVI-statement-on-the-annual-influenza-vaccination-programme-25-July-2012.pdf 
2 Public Health England.  National Childhood Influenza Vaccination Programme 2015 
to 2016 Seasonal influenza vaccine uptake for children of primary school age Final 
data for 1 September 2015 to 31 January 2016. May 2016. 
3 Public Health England.  Childhood Influenza Vaccination Pilot Programme, England 
2014/15: End of season report. April 2016 
4 Sallis, A., Bunten, A., Bonus, A., James, A., Chadborn, T., & Berry, D. (2016). The 
effectiveness of an enhanced invitation letter on uptake of National Health Service 
Health Checks in primary care: a pragmatic quasi-randomised controlled trial. BMC 
Family Practice, 17(1), 1. 
5 Behavioural Insights Team (2014). EAST: Four simple ways to apply behavioural 
insights. 
Cabinet Office Behavioural Insights Team (2012). Applying behavioural insights to 
reduce fraud, error and debt. Cabinet Office, London 
6 Hallsworth M, List J, Metcalfe R, Vlaev I. The Behavioralist As Tax Collector: Using 
Natural Field Experiments to Enhance Tax Compliance. NBER Working Paper 
2014;20007. doi: 10.3386/w20007 
7 N. Shackleton, D Hale, C Bonell and R M Viner. Intraclass correlation values for 
adolescent health outcomes in secondary schools in 21 European countries. SSM -
PopulationHealth2(2016)217–225 
 
 

 
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Appendix 1. Behavioural-insight framed letter 
 

 
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Appendix 2.1. Example 1 invitation letter from 2015/16 season 
 

 
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Appendix 2.2. Example 2 invitation letter from 2015/16 season