The most important results from the study are outlined below. The key terms used in this text are ‘willingness to be vaccinated’ and ‘participation in vaccination’. This means that a person intends and is willing to be vaccinated (willingness to be vaccinated) and whether a person has actually been vaccinated (participation in vaccination, also referred to as vaccine uptake).

Communication and knowledge development
Information channels

• It is important to disseminate information through channels that are appropriate to the target audience. Due consideration should also be given to involving key people, such as a an imam, GP or individuals with first-hand experience.
• A number of youth healthcare service (JGZ) organisations have already worked with key people in the past.

Communication formats

• It is important to consider differences in what information is needed. Some people want concise summaries, while others prefer to dig deeper. 
• Different communication formats can increase willingness to be vaccinated and participation in vaccination. Formats could include recommendations, storytelling and presumptive communication strategies. An example of a presumptive communication strategy is that the care provider phrases the recommendation to be vaccinated in the form of an announcement.
• Among people who are functionally illiterate and groups from different cultural backgrounds, using information materials that are tailored to the linguistic and cultural needs of a specific target audience can be an effective way to increase willingness to be vaccinated and participation in vaccination. 
• In the Netherlands, youth healthcare professionals used specific conversational styles: ‘Shared Decision Making’ or ‘Motivational Interviewing’. The literature review did not reveal any clear evidence to support the effectiveness of ‘Motivational Interviewing’.

Digital interventions

• Interventions that make use of digital gamification or offer health information on a mobile telephone can increase willingness to be vaccinated and participation in vaccination. 
• Youth healthcare services already use digital interventions on a regular basis. Examples include the digital HPV vaccination choice helpline, the digital appointment management system, and digital resources that promote ease of access to information. 

Knowledge development 

• Educational interventions that rely on a familiar and trusted messenger, providing targeted information about disease risks and/or also targeting the parents, can increase willingness to be vaccinated and participation in vaccination. 
• In actual practice in the Netherlands, the main focus is on providing information during a doctor’s appointment or vaccination appointment. Youth healthcare services also organise public information meetings or webinars targeting a specific neighbourhood or target audience.

Refresher training for healthcare professionals

• Refresher training for healthcare professionals can have a positive impact on vaccination coverage. Youth healthcare professionals can attend training sessions to learn techniques for conducting a vaccination talk with parents. They also learn how they can guide parents in making a vaccination choice.

Ease of access
Alternative locations

• The option to administer vaccinations at a location where the target group already goes can lower the threshold for getting vaccinated. This can increase willingness to be vaccinated and participation in vaccination. 

Longer opening hours

• People working in the field and the youth health services (JGZ) consider it important to offer longer opening hours at vaccination sites. Some also offer these additional hours. We have not found any scientific research on a possible relationship between longer opening hours and willingness to be vaccinated and participation in vaccination.

Vaccination reminders

• Vaccination reminders can increase willingness to be vaccinated and participation in vaccination. This applies to various target groups and different forms of reminders, such as SMS, e-mail and letter. 
• A reminder sent to the care provider that a patient will soon reach the next step in the vaccination schedule can also lead to higher willingness to be vaccinated and participation in vaccination. 
• Vaccination reminders are used in actual practice in the Netherlands; this includes SMS reminders prior to a vaccination appointment and phone calls after a missed vaccination appointment. 

Catch-up options

• Offering catch-up options (an extra time when vaccination is possible) can be effective in raising vaccination coverage. This is often seen in combination with a different intervention.
• Catch-up options are offered in actual practice in the Netherlands, for example by offering additional vaccination times during walk-in clinic hours.

Standing orders

• The literature suggests that authorising care providers to administer vaccinations (‘Standing orders’) may be effective in increasing willingness to vaccinate and participation in vaccination.

Combined interventions 

• In combined interventions, multiple intervention strategies are deployed at the same time. These approaches generally seem to work better than interventions based on a single strategy. 
• Combined interventions are already used frequently in actual practice in the Netherlands.