STRATEGIES TO INCREASE THE DEMAND FOR CHILDHOOD VACCINATION IN LOW- AND MIDDLE-INCOME COUNTRIES: A SYSTEMATIC REVIEW AND META-ANALYSIS

Saturday, 23rd of May 2015

“Demand-side strategies to improve vaccination coverage are important because they are inherently equity-oriented and address specific barriers to coverage related to financial constraints, opportunity costs, knowledge and prioritization. Future research should seek to refine our understanding of which approaches are most effective in specific contexts.”

STRATEGIES TO INCREASE THE DEMAND FOR CHILDHOOD VACCINATION IN LOW- AND MIDDLE-INCOME COUNTRIES: A SYSTEMATIC REVIEW AND META-ANALYSIS

Mira Johri ^a, Myriam Cielo Pérez ^b, Catherine Arsenault ^c, Jitendar K Sharma ^d, Nitika Pant Pai ^e, Smriti Pahwa ^f & Marie-Pierre Sylvestre ^a

a. Centre de Recherche du Centre Hospitalier de lUniversité de Montréal (CRCHUM), Tour Saint-Antoine, Porte S03-458, 850 rue St-Denis, Montréal, Québec, H2X 0A9, Canada.
b. Département dadministration de la santé, Université de Montréal, Montréal, Canada.
c. Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Canada.
d. National Health Systems Resource Centre (NHSRC), Ministry of Health and Family Welfare, New Delhi, India.
e. Department of Medicine, McGill University, Montréal, Canada.
f. Pratham Education Foundation (ASER Centre), New Delhi, India.

Correspondence to Mira Johri (email: mira.johri@umontreal.ca).

(Submitted: 08 September 2014 – Revised version received: 05 December 2014 – Accepted: 23 January 2015 – Published online: 23 March 2015.)

Bulletin of the World Health Organization 2015;93:339-346C. doi: http://dx.doi.org/10.2471/BLT.14.146951

Excerpts below; full text, with tables, is at http://www.who.int/bulletin/volumes/93/5/14-146951/en/

Introduction

Almost 40 years after the launch of the World Health Organizations (WHOs) Expanded Programme on Immunization, one in five children worldwide still does not have access to basic vaccines.¹^,² In May 2012, the World Health Assembly approved the Global Vaccine Action Plan to ensure that the full benefits of immunization are extended to people in every region, country and community.¹ Midway through the Global Vaccine Action Plans decade of vaccines (2011–2020)¹, disparities in vaccine coverage within and between countries persist,³ and the search for effective strategies to reach underserved populations has gained urgency.

Interventions to improve vaccination outcomes are commonly grouped into those targeting health services delivery or supply (e.g. improving human resources training, logistics, cold chain maintenance and vaccine storage, effective financing, monitoring and evaluation and supportive supervision) and those that stimulate demand for vaccines (e.g. monetary or food incentives, knowledge transfer or communication campaigns). Certain demand-side interventions have been associated with improved vaccine coverage of children in low- and middle-income countries in previous systematic reviews.⁴^–⁹ However, limitations in study quality and design precluded quantitative synthesis in these reviews. The most recent review considered articles published up to 2009.⁹ In the interim, several new studies of potentially higher quality have been published.

We carried out a systematic review and meta-analysis to evaluate whether demand-side interventions increase uptake of routine childhood vaccination in low- and middle-income countries. Our objectives were to ascertain the effect of demand-side interventions on vaccine coverage and to identify which strategies are effective. We focused on demand-side interventions, since these strategies can more easily reach underserved populations and reduce inequities in immunization coverage.

. . .Discussion

This meta-analysis demonstrates that demand-side interventions lead to an increase in child vaccination coverage in diverse low- and middle-income settings and among communities with lagging health and social indicators. Immunization programmes have often focused on strengthening vaccine supply. Our results show that policymakers who seek to increase access to vaccines through the routine immunization system should also consider demand-side strategies.

Educational or knowledge translation interventions were more effective on average than interventions based on incentives; however, both strategies were effective. The highest estimates of effect and lowest heterogeneity were found among studies with low risk of bias. Risk of bias was related to intervention type, with three of the four incentives studies having moderate-to-high risk of bias.

Our analysis has six important limitations. First, vaccination coverage is shaped by interrelated supply and demand factors. Many studies, particularly those tackling vaccine and non-vaccine outcomes,²⁰^,²¹^,²³^–²⁵ did not give due consideration to the role of the health system in delivering vaccines during the study design phase leading to increased risk of bias. Three supply-side challenges confronted the studies reviewed: (i) increases in demand cannot be effective if supply-side constraints limit provision of vaccines;²¹^,²⁵ (ii) if coverage rates are already very high, there is limited scope to demonstrate improvement;²⁴^,²⁵ and (iii) vaccination rates can be affected by changes in service delivery occurring independently of the study. Among the studies reviewed, only one study did not show a gain associated with the intervention: in this study, all experimental groups experienced substantial but similar gains in vaccination coverage.²³ Another study noted a likely background trend with a differential impact on experimental groups.²⁵ Unfortunately, neither of these studies collected data on health system trends that might affect immunization delivery. Studies addressing vaccine and non-vaccine outcomes, including three of the four incentive based studies²¹^,²⁴^,²⁵ may have faced challenges related to broad study scope or a lack of vaccine-specific expertise in study planning. In addition, two studies of financial incentives²¹^,²⁴ were large-scale interventions and faced substantial implementation challenges.

Second, the systematic review and meta-analysis included only 11 studies. This limited our ability to explore potential sources of heterogeneity quantitatively and to exclude possible biases related to publication and study size.

Third, studies measured different vaccines over different time periods. Receipt of DTP3 is the measure preferred by international agencies to assess immunization coverage and was included in nine of the 11 papers reviewed.³ All analyses consistently showed that demand-side interventions are beneficial in improving coverage. However, due to diversity in outcomes and the small number of studies, we cannot evaluate the effect of interventions for specific vaccines.

Fourth, health gains depend not only on increased vaccine coverage but also on appropriate timing of vaccination. With one exception,²⁵ studies offered little information on when doses were delivered.

Fifth, despite contacting the authors, we were not able to retrieve data for all studies and had to use approximate values for one study²¹ based on another publication.²⁶

Sixth, our analysis excluded interventions that focused exclusively on improving vaccine supply. However, from a policy point of view, how demand-side interventions interact with supply side constraints is also important. With one exception,¹⁸ immunization system performance was not explicitly assessed by these studies.

Our results indicate that future research on demand-side interventions to increase vaccine coverage should (i) standardize measurement of outcomes; (ii) include vaccination experts during the study design phase; and (iii) collect data on health system characteristics that may affect vaccine delivery.

Conclusion

Demand-side interventions are effective in improving the uptake of childhood vaccines delivered through routine immunization services in low- and middle-income countries. Our results are more definitive than those of previous systematic reviews which employed narrative synthesis techniques.⁴^–⁹

Demand-side strategies to improve vaccination coverage are important because they are inherently equity-oriented and address specific barriers to coverage related to financial constraints, opportunity costs, knowledge and prioritization. Future research should seek to refine our understanding of which approaches are most effective in specific contexts. Studies investigating the value of knowledge translation and incentives-based interventions offered in combination are also required. Studies that simultaneously consider supply- and demand-side interventions – and enable us to evaluate their relative effectiveness – are of particular interest. Finally, studies should consider whether interventions can be delivered effectively at scale and in the long term.

Acknowledgements

We thank Diego Bassani, Hospital for Sick Kids, Toronto, Canada.

Funding:

The Canadian Institutes for Health Research (299960) and the Bill & Melinda Gates Foundation (OPP1067851) funded this study.

Competing interests:

None declared.

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