Table 2

Characteristics of eligible studies

Nudging approachAuthors (year, journal)Study locationStudy populationSample sizeStudy designTarget diseaseOutcome measures*
Make available information salientLwembe et al (2016, BMC Family Practice)46UKParents or caregivers of children under 5, policymakers and practitioners31 parents,15 policymakers and 9 practitionersQualitative design: FGD, telephone interviewsNot specific (vaccine-preventable childhood diseases)Perception of the intervention (+)
Borg et al (2018, Vaccine)47AustraliaParents or guardians of children (6 months–<5 years)5534RCTInfluenzaVaccination uptake (influenza vaccine) (0)
Uddin et al (2016, Vaccine)53BangladeshPregnant women, mothers with children aged 0–11 months, and Expanded Program on Immunisation (EPI) service providers in study areas4158Non-randomised (quasi-experimental)Not specific (vaccine-preventable childhood diseases)Vaccination uptake (all childhood vaccines) (+)
Ahlers-Schmidt et al (2012, Vaccine)54USAParents of newborns90RCT (pilot study)Not specific (vaccine-preventable childhood diseases)Vaccination uptake (all childhood vaccines) (−)
Kim et al (2018, JAMA Network Open)56USAAdult patients96 291Quantitative descriptive study (Quality improvement)InfluenzaVaccination uptake (influenza vaccine) (+)
Patel et al (2017, Journal of General Internal Medicine)55USAAdults45 926Non-randomised (observational study)InfluenzaVaccination uptake (influenza vaccine) (+)
Changolkar et al (2020, PLoS One)57USAPrimary care physicians from 10 primary care practices56Non-randomised study (quasi- experimental)InfluenzaVaccination uptake (influenza vaccine) (+)
Duvall (2019, Pediatric Nursing)58USAFamilies of paediatric inpatients older than 6 months of age, physicians and nurses173Quantitative descriptive study (quality improvement)InfluenzaVaccination uptake (influenza vaccine) and perception of intervention (+)
Milkman et al (2011, Proceedings of the National Academy of Sciences of the USA (PNAS))59USAEmployees aged >50 years3272RCTInfluenzaVaccination uptake (influenza vaccine) (+)
Kempe et al (2013, American Journal of Public Health)60USAParents of children who were aged 19–35 months31 567RCTNot specific (vaccine-preventable childhood diseases)Childhood immunisation status (up to date) and cost-comparison benefit (+)
Szilagyi et al (2020, JAMA Internal Medicine)61USAPatients in 52 primary care practices164 205RCTInfluenzaVaccination uptake (influenza vaccine) (+)
Porter et al (2018, Vaccine)63USAParents with daughters aged 9–17 years761RCTHPVIntention to vaccinate and vaccine confidence (−)
Saitoh et al (2017, Human Vaccines and Immunotherapeutics)62JapanPregnant women160RCTInfluenza and PCV13Parental attitudes and beliefs towards vaccines and their infant’s vaccination uptake (0)
Joseph et al (2016, Clinical Pediatrics)64USAMothers with daughters aged 11–15 years200RCT (pilot study)HPVVaccination uptake (HPV vaccine) and knowledge about vaccines (−)
Staras et al (2021, BMC Public Health)48USAParents of adolescents aged 11–12 years286RCT (feasibility trial)HPVFeasibility and acceptability of vaccine reminders (+)
Lorini et al (2020; Vaccines)50ItalyNursing home workers1998Mixed-methods studyInfluenzaIntention to vaccinate (influenza vaccine) (+)
Schmidtke et al (2020, BMJ Quality and Safety)52UKHealthcare workers7540RCTInfluenzaVaccination uptake (influenza vaccine) (−)
Chen et al (2020; Behavioural Public Policy)51USAAdults aged 65–70 years208 867RCTInfluenza, tetanus, shingles and pneumoniaVaccination uptake (influenza, shingles, tetanus, pneumonia vaccine) (+)
Milkman et al (2021, PNAS)49USAPatients in 2 large health facilities47 306RCTInfluenzaVaccination uptake (influenza vaccine) (+)
Maltz and Sarid (2020, Medical Decision Making)66IsraelAdults aged 18–65 years3271RCTInfluenzaIntention to vaccinate (influenza vaccine) (+)
Panozzo et al (2020, Journal of Adolescent Health)65USAMothers with children aged 11–14 years762RCTHPVIntention to vaccinate (HPV vaccine) (−)
Change the way outcomes are framedLechuga et al (2011, Annals of Behavioural Medicine)77USAMothers with daughters aged 9–17 years150Mixed-methods design (formative and experimental study)HPVIntention to vaccinate (HPV vaccine) (+)
Fahy and Desmond (2010, Irish Journal of Medical Science)76IrelandMothers with daughters aged 8–16 years72Non-randomised study (single group pre-test and post-test)HPVAttitudes towards vaccine and intention to vaccinate (HPV vaccine) (0)
Liu et al (2019, Patient Education and Counselling)79ChinaWomen aged 18–45 years453Quantitative descriptive study (Survey)HPVIntention to vaccinate (HPV vaccine) (0)
Frew et al (2014, Vaccine)81USAPregnant women272RCTInfluenzaIntention to vaccinate (influenza vaccine) (−)
Hendrix et al (2014, Pediatrics)82USAParents with an infant <12 months of age802RCTMMRIntention to vaccinate (MMR vaccine) (+)
Motta et al (2021, Frontiers in Political Science)44USAAdults7064RCTCOVID-19Intention to vaccinate (COVID-19 vaccine) (+)
Freeman et al (2021, The Lancet Public Health)78UKAdults (vaccine hesitant)18 855RCTCOVID-19Intention to vaccinate (COVID-19 vaccine) (+)
Xu et al (2020, Aslib Journal of Information Management)80ChinaCollege students300Non-randomised study (quasi-experimental)HPVIntention and information need to vaccinate (HPV vaccine) (+)
Okuno et al (2021, Pediatrics International)83JapanMothers81RCTHaemophilus influenzae type b (HiB) and pneumonia (PCV)Intention to vaccinate (HiB and PCV vaccines) (−)
Invoke social normsLee et al (2018, Applied Nursing Research)84USAMothers and daughters aged 14–17 years18 dyads (mother and daughter)Mixed-methods design (community-based participatory research with pilot RCT)HPVIntention to vaccinate and vaccination uptake (HPV vaccine) (0)
Attwell and Freeman (2015, Vaccine)85AustraliaParents with children304Mixed-methods design (evaluation study)Not specific (vaccine-preventable childhood diseases)Attitudes towards vaccine (−)
Encourage emotional affectPapapchrisanthou and Loman (2018; Public Health Nursing)86USAParents of infants aged 4–14 days40Non-randomised studyDTaP, Polio, Influenza, Hepatitis B and PneumoniaParental perception of immunisations, perceived knowledge of disease, comfort with immunisation decision making, satisfaction with provider and vaccine schedule adherence (0)
Blanchard et al (2020, Journal of Public Health)87USAAdolescents aged 13–18 years598Non-randomised study (single group pre-test and post-test)Not specific (vaccine-preventable childhood diseases)Knowledge, attitudes and beliefs about vaccines (+)
Kuru et al (2021, PLoS One)88USAAdults2345RCTMMRVaccine intentions (MMR vaccines) (+)
Nyhan et al (2014, Pediatrics)91USAParents with children aged <17 years2229RCTMMRPerception about vaccine’s safety and intention to vaccinate (MMR vaccine) (−)
Kepka et al (2011, Journal of Community Health)89USAParents with daughters aged 9–17 years88RCTHPVVaccination awareness and uptake (HPV) (+)
Cox et al (2010, Health Psychology)90USAMothers with daughters aged 11–16 years522RCTHPVIntention to vaccinate (HPV) (+)
Change defaultsGiubilini et al (2019, HEC Forum)73UKGeneral population (61.9% are parents with children)457Quantitative descriptive study (survey)MMRVaccination policy at schools (+)
Reiter et al (2012, Journal of Behavioural Medicine)74USAParents with adolescent sons aged 11–17 years404RCTHPV, influenza and meningococcemiaIntentions to vaccinate (HPV, seasonal influenza and meningococcal vaccine) (0)
Brewer et al (2017, Pediatrics)72USAPrimary care clinics with patients aged 11 or 12 years29RCTHPVVaccination uptake (HPV vaccine) (+)
Opel et al (2015, American Journal of Public Health)71USAPaediatric providers and parents of children aged 1–19 months16Non-randomised (cross-sectional observational study)Not specific (vaccine-preventable childhood diseases)Parental verbal acceptance of recommended vaccines at visit’s end (0)
Offer incentivesZeng et al (2019, Vaccine)67ChinaParents with young children aged 3–6 years1506Non-randomised (cross-sectional survey)InfluenzaIntention to vaccinate (influenza vaccine) (+)
Buttenheim et al (2016, Vaccine)45USAParents and caregivers of infants95RCT (feasibility study)TdapVaccination uptake (Tdap) (−)
Bronchetti et al (2015, Journal of Economic Behaviour and Organisation)68USACollege students9358RCTInfluenzaIntention to vaccinate (influenza vaccine) (0)
Rockliffe et al (2020, PLoS One)69UKStudents aged 13–14 years36 students (n=6 FGDs), 181 studentsQualitative designHPVAcceptability of financial incentives (0)
Banerjee et al (2010, BMJ)70IndiaHouseholds with children 0–5 years2188RCTNot specific (vaccine-preventable childhood diseases)Vaccination uptake (all childhood vaccines)
Change the messengerSchoeppe et al (2017, Health Promotion Practice)75USAParent advocates33 (across three study years)Mixed-methods design (evaluation study)Not specific (vaccine-preventable childhood diseases)Knowledge, attitudes and behaviour on vaccines (+)
  • *The sign in the brackets indicates whether the results support the effectiveness of the respective intervention (+), indicate negative evidence for the effectiveness (−) or the results are mixed (0).

  • † Used an additional nudge - ‘Change the messenger’

  • ‡ Used an additional nudge - ‘Invoke social norms’

  • DTaP, diptheria, tetanus and accelular pertussis; FGD, focus group discussion; MMR, measles, mumps and rubella; PCV13, pneumococcal conjugate; RCT, randomised controlled trial; Tdap, tetanus, diphtheria and pertussis.