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WHAT'S NEW THIS THURSDAY: PREDICTION OF IMMUNIZATION PERFORMANCE

Tuesday, 19th of February 2013

WHAT’S NEW THIS THURSDAY: PREDICTION OF IMMUNISATION PERFORMANCE

The Lancet, Volume 381, Issue 9864, Pages 349 - 350, 2 February 2013

Original Text

Celina M Hanson a, Eliane Furrer b , Nina Schwalbe b, Seth Berkley b

Also at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)62165-5/fulltext

Vaccines are extremely powerful disease prevention agents and have the potential to save millions of lives. Tremendous scientific progress has been made in the past decade with several new vaccines licensed, including those to prevent pneumococcal and rotavirus disease—the two leading killers of young children in developing countries. Thanks to concerted efforts by stakeholders through the GAVI Alliance, many of these new vaccines are now accessible to the lowest-income countries and the children who live there.

However, we have not achieved equity in access to vaccines. Although routine immunisation coverage rates have substantially increased over the past two decades,1 nearly one in five children still does not receive even the most basic childhood vaccines.2 In 2011, an estimated 83% (107 million) of infants worldwide were vaccinated with three doses of diphtheria-tetanus-pertussis (DTP3) vaccine.2 More than 75% of the 22·4 million unvaccinated children live in the 56 countries eligible for GAVI support. Within these countries those who are not reached tend to be the poorest, the most vulnerable, and at times the most marginalised subgroups of the population.2

Increased immunisation efforts can bring us closer to reaching the Millennium Development Goal (MDG) 4 target of reducing child mortality by two-thirds. But greater efforts are needed on two fronts: acceleration of the uptake of underused and newly available vaccines, and strengthening of the immunisation system to improve overall routine immunisation coverage.

The GAVI Alliance has been successful in accelerating the uptake of underused and newly available vaccines, but have we identified effective ways to tackle the strengthening of the immunisation system? What are the factors that affect immunisation performance in low-resource settings? Are poor countries inevitably worse off when it comes to delivery of life-saving vaccines to the entire population?

A look across GAVI-eligible countries is revealing. Although, on average, GAVI-eligible low-income countries tend to have lower coverage rates for the third dose of DTP vaccine—often used as a proxy for immunisation system performance—and higher drop-out rates between the first and third vaccine doses than do wealthier non-GAVI-eligible countries, there are notable exceptions. Seven countries—Burundi, Malawi, Eritrea, Nepal, Tanzania, Rwanda, and Burkina Faso—are classified as among the 20 poorest countries in the world with annual income levels less than US$600 per head, yet they all had estimated DTP3 coverage rates at or greater than 90% in 2011.2 Although we acknowledge varying degrees of confidence in these estimates, they are an interesting divergence from general trends and require us to delve deeper to understand the factors associated with weak immunisation systems.

A GAVI internal assessment has shown that immunisation performance, as indicated by DTP3 coverage, DTP1—3 drop out, and number of new vaccines adopted, is not statistically different between fragile and non-fragile states. Of the 14 GAVI-eligible countries with DTP3 coverage of less than 70% in 2010, eight were considered by one or more definitions to be fragile states and six were not. When comparing GAVI-eligible fragile states with other low-performing countries there is no clear demarcation in vaccination performance across countries categorised as fragile and those as non-fragile. Low income levels and political fragility seem to be possible causes for low immunisation performance, but are certainly not the only determining factors in all circumstances.

A study explored the effect of new and underused vaccine introduction on routine immunisation performance as measured by DTP3 coverage in infants, and showed no association.3 This is an encouraging finding because some feared that addition of new vaccines to the national programme would weaken the immunisation system and negatively affect routine coverage.

Cross-national studies show general associations between development status and immunisation outcomes. For example, we noted sizable differences in several socioeconomic indicators when comparing low-performing (<70% DTP3 coverage and >10% drop out) with high-performing (>80% DTP3 coverage and <5% drop out) countries. Countries with lower immunisation performance on average had lower ratios of girls to boys enrolled in primary school, lower female literacy rates, and lower scores on a range of governance indicators compiled by the World Bank, such as rule of law, and political stability and absence of violence.4Although these results cannot establish causality or association, they provide interesting findings and point to the interdependence of development inputs and outcomes. The GAVI Alliance has started to explore more comprehensively the underlying causes of weak immunisation performance and is defining country-specific strategies to become more effective in countries that are lagging.

A lot can be learnt from so-called positive deviants5—countries that manage well despite seemingly unfavourable circumstances. We encourage the global community to intensify research into the factors determining high immunisation performance, to define the incentives that can be put in place to replicate success in other countries, and to strengthen routine service delivery more effectively.

EF, NF, and SB are employed by the GAVI Alliance. We declare that we have no conflicts of interest.

References

1 Duclos P, Okwo-Bele J-M, Gacic-Dobo M, Cherian T. Global immunization: status, progress, challenges and future. BMC Int Health Hum Rights 2009; 9: S2. PubMed

2 WHO, UNICEF. Global immunization data—summary: global immunization coverage in 2011.http://www.who.int/immunization_monitoring/Global_Immunization_Data.pdf. (accessed Sept 10, 2012).

3 Shearer JC, Walker DG, Risko N, Levine OS. The impact of new vaccine introduction on the coverage of existing vaccines: a cross-national multivariable analysis. Vaccine 2012; 30: 7582-7587. CrossRef | PubMed

4 World Bank. Worldwide governance indicators. http://info.worldbank.org/governance/wgi/index.asp. (accessed June 5, 2012).

5 Pascale R, Sternin J, Sternin M. The power of positive deviance: how unlikely innovators solve the world's toughest problems. Cambridge: Harvard Business Press, 2010.

a Global Institute of Public Health, New York University, NY, USA

b GAVI Alliance, Chemin des Mines 2, Geneva 1202, Switzerland