What Works to Increase Uptake of Childhood Immunization: A Rapid Evidence Assessment of the Impact of Interventions Targeting Caregivers, Healthcare Workers and Communities

"The selection of interventions needs to be tailored to the local population, but multicomponent interventions were found to be consistently effective."

In the first decades of the 21st century, coverage levels of essential childhood vaccines have plateaued and even declined in some parts of the world. Moreover, shocks to public health systems, including the COVID-19 pandemic, have adversely affected vaccine uptake in many regions and have highlighted substantial pockets of coverage inequities. For example, vulnerable and marginalised (e.g., Roma) communities in Europe and Central Asia face specific issues with respect to vaccination, such as mistrust of health institutions. Published by the United Nations Children's Fund (UNICEF) Regional Office for Europe and Central Asia (ECARO) and UNICEF Innocenti, this rapid evidence assessment (REA) synthesises the published literature on interventions for caregivers, healthcare workers (HCWs), and communities to answer the question of "what works" to increase uptake of immunisation services for children 5 years and younger. The findings have global relevance but were also used to make more specific recommendations to address challenges identified in consultations with UNICEF's ECARO.

With a global scope, this REA has 2 research questions: (i) how effective are interventions that reach out to caregivers, HCWs, and the community to increase vaccination rates of children 5 years old and younger; and (ii) what evidence is available linking intermediate vaccination outcomes (such as intention and motivation to vaccinate) and vaccination uptake? The review included 48 systematic reviews and 21 primary studies published from 2015 to 2022. Studies were only included if there was a comparative component - be it another intervention, a before-and-after comparison, or compared with no additional intervention (i.e., standard of care). Systematic reviews were the main study design of interest; however, to fill a synthesis gap, the team also included primary studies assessing HCW incentives. Among these 21 included primary studies, 8 were cluster randomised controlled trials (RCTs), and the remainder were quasi-experimental studies.

Broadly, for vaccination outcomes, the team identified some or sufficient evidence on the effectiveness for several interventions, including: caregiver education alone or in combination with other interventions; home visits alone or in combination; HCW training in combination; HCW material and non-material incentives used in combination; and community outreach and collaboration, both alone and in combination. Multicomponent interventions were found to be consistently effective.

More specifically:

1. Interventions for caregivers
   • Caregiver information or education: There is insufficient evidence to determine if caregiver education has an impact on intention to vaccinate or caregiver knowledge when used alone or in combination with other interventions. However, there is sufficient evidence of the effectiveness of caregiver education on vaccination uptake when used alone or in combination with other interventions. Combination interventions included combinations with other interventions of interest to this REA (e.g., home visits, community outreach, HCW education) as well as other interventions aiming to increase vaccination uptake (reminders, recall, health system changes). Results from meta-analyses conducted by authors of the included systematic reviews suggest that these interventions may be more effective in low- and middle-income countries (LMICs) when delivered as discussions and when delivering one rather than multiple vaccines. Some review authors indicated that caregiver education-based interventions are most effective when knowledge and awareness are the main barriers to vaccination.
   • Caregiver non-material incentives: No studies were identified that assessed the impact of non-material incentives for caregivers within the search period.
   • Home visits: Insufficient evidence was found to determine the effectiveness of home visits in combination with other interventions on caregiver knowledge. No studies reported data on other intermediate outcomes. There is some evidence that home visits used alone increases vaccination uptake and sufficient evidence that home visits in combination with other interventions increases vaccination outcomes. Examples of interventions used in combination with home visits include community outreach, health system improvements, HCW education, HCW incentives, and caregiver reminders. The results of a meta-analysis suggest that providing specific vaccination advice during home visits has a significant positive effect on vaccination outcomes.
2. Interventions for HCWs
   • HCW training and education: 19 systematic reviews were identified that included studies assessing HCW training and education to increase vaccination-related outcomes. There is insufficient evidence to determine if HCW training used alone or in combination with other interventions impacts intermediate outcomes. There is sufficient evidence that HCW training, when combined with other interventions, can have a positive effect on vaccination outcomes, but insufficient evidence to determine when used alone. Many combination interventions were used across the systematic reviews, but examples of interventions used with HCW training include community outreach, health system strengthening and reminders (both for HCWs and caregivers).
   • HCW non-material incentives: There was insufficient evidence from systematic reviews to determine effectiveness of non-material incentives when used alone on vaccination outcomes. Evidence from primary studies found no evidence of effect (n=5) or had mixed results (n=1). There is some evidence that non-material incentives, when combined with other interventions, can have a positive effect on vaccination uptake. Examples of interventions used in combination with HCW non-material incentives include reminder and recall, HCW financial bonuses, and training on missed opportunities to immunise.
   • HCW material incentives: There is some evidence to support the use of this intervention when combined with other strategies, but insufficient evidence to determine the effectiveness for use on its own. Interventions used in combination with HCW material incentives included non-material incentives, HCW training, caregiver education, and improvements to vaccine accessibility and availability. One high-quality meta-analysis found a significant positive effect of bonus payments and enhanced fee-for-service paid to outpatient healthcare providers.
3. Community-based interventions
   • Community collaboration and outreach: While there is insufficient evidence to determine whether community collaboration or outreach used alone or in combination influences caregiver attitudes, knowledge, or awareness, there is sufficient evidence on the effectiveness of community collaboration or outreach used alone or in combination with other interventions on vaccination outcomes. Community collaboration or outreach was combined with many different interventions across the 31 systematic reviews, including HCW training, reminders, caregiver incentives, caregiver education, and health system changes.
   • Community subgroups: There is insufficient evidence to determine whether outreach to faith-based communities used alone or in combination impacts intermediate or vaccination outcomes. Only 2 systematic reviews included studies that assessed populations on the move; therefore, there was insufficient evidence to determine the effectiveness on either intermediate or vaccination outcomes.

Of these interventions for which some or sufficient evidence of impact on vaccination outcomes was found, the most applicable to the barriers in Europe and Central Asia may be caregiver education, home visits, and community collaboration and outreach. Caregiver education could address the issues of lack of information in some countries in the region and may improve attitudes, knowledge, and uptake of vaccination. This intervention may be most effective in populations whose baseline education is low, and when delivered face-to-face. Community outreach and home visits reduce the distance between services and caregivers and may be particularly relevant for populations where access is the main barrier to vaccination uptake. Given the distrust between caregivers, HCWs, and the government in some countries in Europe and Central Asia, collaboration with trusted community organisations may be useful to harness pre-established relationships.

The REA identified gaps in the evidence published from 2015 onwards. For example:

• Studies are needed that analyse behavioural interventions designed to change HCW vaccination attitudes and how these interventions could impact HCW motivation to deliver vaccination or to recommend it to caregivers.
• Rigorous studies are required to evaluate how interventions for caregivers or HCW can affect vaccination-related service quality and experience.
• Trials or rigorous evaluations of interventions delivered at the community level, and their effects on social or community norms, should be conducted. To provide a full understanding, studies should not rely only on qualitative or descriptive norms but should attempt to find proxy measures of norms that could be comparable across studies.
• Additional primary research is needed on the effect of community interventions on intermediate outcomes to understand the causal chain.
• The team did not identify any systematic reviews focusing on interventions using social media and online communities as a method to disseminate information to caregivers and communities. Evidence synthesis will be important to understand the utility of these interventions to alter vaccination behaviours.
• There were a limited number of studies identified that were undertaken in European and Central Asian countries. Studies are needed in this region.

The report also considers the implications of the research identified in the REA on practice. Each intervention category is discussed separately, both in general and in relation to the determinants of low vaccine uptake in Europe and Central Asia. Here are some highlights:

• Interventions for caregivers: Health promotion materials should address knowledge deficits specific to the population using materials that are not complex and are culturally and linguistically appropriate. There is evidence that discussion rather than written education may be more effective, though costly and time-consuming. In some European and Central Asian countries, there is mistrust between caregivers, HCWs and the government; therefore, consideration needs to be given to who will deliver the information.
• Interventions for HCWs: Training and educating health providers could be regarded as a cross-cutting intervention to support provider, caregiver, and community members' behaviour change objectives and to attain health system strengthening. In Europe and Central Asia, caregivers perceived that HCWs lacked knowledge and were vaccine hesitant; it is unclear if HCW training and education would improve caregiver perceptions. Policymakers should keep in mind that there is a natural link between training, feedback, performance, and reward, and they should develop interventions for HCWs that treat these aspects in a holistic manner.
• Interventions for communities: Providing community-based interventions as a single strategy or in combination could be a useful approach in Europe and Central Asia, where mistrust among caregivers, HCWs and the government may represent a barrier to vaccination. Community members also have local knowledge that can be leveraged to adapt interventions to meet community needs. In addition, Omoniyi and Williams (2020) observed that in some settings, community leaders enjoy legitimacy that political leaders do not.

Concluding notes:

• Barriers to vaccination are multidimensional; therefore, having multiple components allows several determinants of low vaccine uptake to be tackled simultaneously. Interventions need to be selected based on the contextual factors of the local population and be specific to addressing their barriers.
• In addition to the effectiveness of the interventions explored in the REA, policymakers may need to consider other factors not explored in this review, including costs and cost-effectiveness, assimilation (of the strategy into existing systems), and sustainability.
• The order that interventions are implemented may be important; for example, if system improvements are needed, these may need to be addressed before HCW training or caregiver communication interventions are carried out.