Routine immunisation of children in LMICs: EGM
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Immunisation is one of the most cost-effective interventions to prevent and control life-threatening infectious diseases among children. Nonetheless, rates of routine vaccination of children in low- and middle-income countries (L&MICs) are strikingly low or stagnant.. Identifying effective strategies for improving coverage and timeliness of routine child immunisation is therefore a priority for many L&MIC governments and the global health community at large. This evidence gap map (EGM) report presents the findings of a systematic evidence mapping exercise to characterise the evidence base on routine child immunisation in L&MICs.
This EGM includes evidence from impact evaluations and systematic reviews assessing the impact of any intervention on any of the following outcomes in low- or middle-income countries:
- Coverage or timeliness of routine vaccinations in children under five
- Child morbidity or mortality from vaccine-preventable diseases
- Intermediate outcomes related to the behavioural, social and practical barriers faced by caregivers and communities to get their children vaccinated or the capacity of health systems to deliver quality vaccination services
The interventions and outcomes are grouped into a three-level hierarchy and arranged in a matrix of 38 unique intervention categories and 43 unique outcome categories.
Interventions are grouped by who or what is targeted: caregivers, the health system, non-caregiver community members, the community as a whole, and or policies and institutions beyond the health system. Outcomes are grouped by whether they concern final outcomes (vaccination coverage/timeliness or health outcomes), demand-related intermediate outcomes, or supply-related intermediate outcomes.
We implemented a broad and systematic search of academic databases and institutional websites, yielding 46,096 records. We de-duplicated these results and used a standardised protocol to screen titles/abstracts for inclusion. We then reviewed the full texts of studies included on title/abstract to identify included studies. Using a standardised data extraction protocol, we coded studies for the countries where they were conducted, the interventions/outcomes studied, their analysis methods, and their attention to equity. We also conducted critical appraisals of all systematic reviews and assigned each review a confidence rating of high, medium, or low. We used the extracted data to identify patterns in the distribution of evidence, including interventions or outcomes that have been inadequately studied through impact evaluation (absolute evidence gaps), or where there are a number of impact evaluations but no high-confidence systematic reviews (synthesis gaps).
We identified 226 completed impact evaluations, 24 ongoing impact evaluations, 60 completed systematic reviews, and 1 ongoing systematic review. There has been a noticeable but sporadic upward trend in the amount of evidence produced per year over the last 15 years.
Evidence is concentrated in a relatively small number of countries: only five countries (India, Nigeria, Kenya, Pakistan, and Bangladesh) have been the site of more than 10 impact evaluations. Evidence is most prevalent in Sub-Saharan Africa and South Asia, with relatively little evidence from the East Asia/Pacific and Middle East/North Africa regions. Many of the countries with the lowest coverage of routine vaccinations also have very thin or non-existent evidence bases.
We find that the most frequently studied interventions are those related to education or incentives for caregivers and health providers, and to health system governance. There is a notable gap in evidence on interventions to increase vaccination coverage among migrant, refugee, or vaccine-hesitant populations. There is also little evidence on interventions to improve health workers’ motivation, apart from monetary incentives and pay-for-performance schemes. While strategies for engaging communities through community dialogues to increase vaccination coverage are fairly well studied, there have been few impact evaluations or systematic reviews on enlisting local leaders (such as religious leaders) to promote vaccination, or on the use of community resources for registering children eligible to receive vaccinations and tracking those due for vaccinations. There is also a potential synthesis gap with respect to incentives for health providers. Besides gaps in evidence on interventions, there is also a notable gap in information of their costs and any form of cost-effectiveness or cost-benefit analysis.
Among outcomes, we find that vaccination coverage/timeliness are mostly very well studied, though coverage of zero dose children has been minimally assessed. While we found fewer studies on morbidity and mortality than for coverage/timeliness, these health outcomes are nevertheless fairly well represented in the literature.
The major outcome evidence gaps are related to intermediate outcomes. Although there have been a number of impact evaluations examining caregivers’ knowledge about immunisation and their retention of vaccination cards, very few studies have examined other outcomes related to behavioural, social and practical barriers faced by caregivers. For example, the cost and convenience of vaccinating, caregivers’ attitudes about health providers, social norms or their perceptions of vaccination side effects. There are also major gaps with respect to supply-side intermediate outcomes. There is little evidence on supply chain management, defaulter tracing, the supply of formal health workers, or the capacity of health system administrators. There are potential synthesis gaps regarding outcomes related to health workers’ motivation, capacity, and performance, and to vaccine stockouts.
Relatively few studies address equity by evaluating an intervention targeting a vulnerable group or by conducting sub-group analysis. We analysed the proportion of studies that address equity in four key areas: hard-to-reach populations, sex of the child, socioeconomic status, and maternal education level. For each of these categories, only 10-15% of impact evaluations and systematic reviews addressed them
