Table 1 Behavioural-science informed changes to the flu invitation letter and their rationale

Reduced in length and made simpler.

Simplification: Reduces the cognitive effort required to process the information and identify the action required [25].

Formatted text to highlight the key points of note/ actions required.

Salience: Reduces cognitive effort to identify action required [26,27,28].

GP practice named

Messenger effect: NHS is a trusted brand when it comes to medical/ health issues. (BCT 9.1 Credible Source [24])

Tear-off appointment time slip

Action Planning: Addressing implementation intentions by providing a tear off slip to record the date time and location of the appointment [29]. Parent actively commits to implement intention as they write down the date, time and location of the appointment. (BCT 1.4 Action Planning [24])

Dear [Name]

Personalisation: Increases personal relevance and focuses attention.

«Insert child’s first name»‘s annual flu vaccination is now due

Personalisation and personal salience: Using Child’s name increases personal relevance and stating ‘due’ creates a sense of urgency.

This vaccination programme is in place to help protect your child against flu.

Gain-framed message: evidence indicates gain-framed messages may be more effective than loss-framed for preventative behaviours (BCT 13.2 Framing [24])

Flu can be an unpleasant illness and sometimes causes serious complications.

Information about Health Consequences and Salience of Consequences: highlighting the negative effects of flu (BCT 5.1 Information about Health Consequences and 5.2 Salience of consequences [24])

Vaccinating your child will also help protect more vulnerable friends and family by preventing the spread of flu.

Providing information about social and environmental consequences: making it personally relevant. Framing/Reframing: framing the child’s vaccination in terms of protecting other loved ones in order to change emotions about performing the behaviour (BCT 5.3 Information about social and environmental consequences, 13.2 Framing [24])

Please phone [insert number] to book an appointment for [insert child’s name]‘s flu vaccination.

Action orientated: providing clear action focused instruction including telephone number to make the behaviour easy to perform and providing child’s name to increase personal salience (BCT 4.1 Instruction on how to perform a behaviour [24])

The vaccination is free and recommended for young children …

Framing/ Reducing friction: to perform the behaviour: Reduces friction costs by eliminating the barrier of cost since 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. (BCT 13.2 Framing, 6.3 Information about others’ approval [24])

… and will be given by a quick and simple spray up the nose

Framing effect: Encouraging uptake of this method because it is appealing and not painful (compared to traditional ideas of a vaccination being an invasive injection) (BCT 13.2 Framing [24])