Elsevier

The Lancet

Volume 372, Issue 9655, 13–19 December 2008, Pages 2031-2046
The Lancet

Articles
Tracking progress towards universal childhood immunisation and the impact of global initiatives: a systematic analysis of three-dose diphtheria, tetanus, and pertussis immunisation coverage

https://doi.org/10.1016/S0140-6736(08)61869-3Get rights and content

Summary

Background

Substantial resources have been invested in increasing childhood immunisation coverage through global initiatives such as the Universal Childhood Immunisation (UCI) campaign and the Global Alliance on Vaccines and Immunisations (GAVI). There are longstanding concerns that target-oriented and performance-oriented initiatives such as UCI and GAVI's immunisation services support (ISS) might encourage over-reporting. We estimated the coverage of three doses of diphtheria, tetanus, and pertussis vaccine (DTP3) based on surveys using all available data.

Methods

We estimated DTP3 coverage by analysing unit record data from surveys and supplemented this with reported coverage from other surveys and administrative data. We used bidirectional distance-dependent regression to estimate trends in survey-based coverage in 193 countries during 1986–2006. We used standard time-series cross-sectional analysis to investigate any association in the difference between countries' official reports and survey-based coverage as the dependent variable and the presence of GAVI ISS as the independent variable, controlling for country and time effects.

Findings

Crude coverage of DTP3 based on surveys increased from 59% (95% uncertainty interval 51–65) in 1986 to 65% (60–68) in 1990, 70% (65–74) in 2000, and 74% (70–77) in 2006. There were substantial differences between officially reported and survey-based coverage during UCI. GAVI ISS significantly increased the difference between officially reported coverage and survey coverage. Up to 2006, in 51 countries receiving GAVI ISS payments, 7·4 million (5·7 million to 9·2 million) additional children were immunised with DTP3 based on surveys compared with officially reported estimates of 13·9 million. On the basis of the number of additional children immunised from surveys at a rate of US$20 each, GAVI ISS payments are estimated at $150 million (115 million to 184 million) compared with actual disbursements of $290 million.

Interpretation

Survey-based DTP3 immunisation coverage has improved more gradually and not to the level suggested by countries' official reports or WHO and UNICEF estimates. There is an urgent need for independent and contestable monitoring of health indicators in an era of global initiatives that are target-oriented and disburse funds based on performance.

Funding

Bill & Melinda Gates Foundation.

Introduction

In many countries, vaccine-preventable diseases remain major causes of child mortality.1 Delivery of childhood immunisations is an essential dimension of health systems and is included as an indicator for Millennium Development Goal 4. Overall performance of immunisation programmes has most often been tracked with the coverage of three doses of diphtheria, tetanus, and pertussis vaccine (DTP3).

Over the past 30 years, substantial resources have been invested through global initiatives to scale up immunisation coverage.2, 3 In 1974, WHO launched the Expanded Programme on Immunisation (EPI).4 After this programme, in 1977, a global goal for universal child immunisation against the six basic antigens (measles, poliomyelitis, diphtheria, pertussis, tetanus, and tuberculosis) was articulated at the World Health Assembly.4 In 1984, UNICEF in partnership with others launched the Universal Childhood Immunisation (UCI) by 1990 initiative, defined as 80% immunisation coverage.2 UCI mobilised substantial funds and support for delivery of immunisation services and, in 1990, UNICEF declared that UCI's target had been achieved.5

In the 1990s, estimates suggested that improvements in immunisation coverage were stagnating or falling.2, 6, 7 In response, the Global Alliance on Vaccines and Immunisations (GAVI), a public–private partnership that aims to increase coverage of basic vaccines and to accelerate the introduction of new vaccines in low-income and middle-income countries, was launched in 1999. Although GAVI provides a range of support, immunisation services support (ISS) is the funding that aims to increase coverage of basic vaccines such as DTP3. ISS is provided in response to country proposals and represents flexible cash that countries can use to improve immunisation performance.8

ISS payments are performance-based, with funds disbursed in proportion to the number of additional children less than 1 year of age targeted or reported to receive DTP3. Payments are divided between two phases: an investment phase (the first 2 years after a country's proposal has been approved) and a reward phase (the third year and onwards after approval).8 During the investment phase, US$20 is disbursed per additional child targeted by the country to receive DTP3 in the first year following approval of GAVI support. The baseline for determination of the additional number is the number of children receiving DTP3 in the year before the approval of ISS. In the reward phase, GAVI disburses $20 per additional child reported by countries to receive DTP3, compared with the target set during the investment phase or the number of children receiving DTP3 in the previous year if this number is higher.

The number of additional children receiving DTP3 is based on official reports from countries to WHO and UNICEF. These reports are largely but not exclusively based on administrative data from health-service-provider registries. In recognition of the weakness of administrative data systems and the potential for ISS to induce incentives for over-reporting, GAVI requires countries to pass a data quality audit (DQA) of their administrative data system to be eligible for reward payments.8, 9 DQAs are used to assess the accuracy of reports from health centres to districts and nationally on the number of additional children immunised with DTP3 by comparing this number against a re-count of paper records in health centres.9

Sample surveys are the other main source of data on immunisation coverage. These include standardised multicountry surveys, such as the demographic and health surveys (DHS), as well as country-specific surveys, such as the EPI 30-cluster by seven household surveys. Using both officially reported data and survey data, WHO and UNICEF jointly publish estimates of national and global DTP3 immunisation coverage.10, 11, 12 WHO and UNICEF estimates aim to reconcile differences between reported and survey data; however, their estimation is not undertaken in a reproducible way and nor do they include an estimation of uncertainty for the measurement of coverage.

There are several lingering concerns about the measurement of coverage. The quality of administrative data on immunisation coverage remains suspect due to problems with measurement,13 as well as the potential for target-oriented initiatives such as UCI2, 14, 15 and performance-based payment systems such as GAVI's ISS2, 7 to encourage health-service providers to over-report coverage. A previous analysis16 did not detect an effect of GAVI ISS on over-reporting, measured as the difference between officially reported and survey-based coverage; however, new data are now available to assess this effect in a larger number of countries.

In this study we seek to address these concerns by using all available data to systematically assess the survey-based trend in DTP3 crude coverage with uncertainty intervals during 1986–2006; and whether global health initiatives, such as UCI and GAVI ISS, lead to over-reporting of DTP3 immunisation coverage.

Section snippets

Data and definitions

We did a systematic search for data to estimate the coverage of DTP3 immunisation during 1980–2006. Available data fall into five categories: first 225 standardised multicountry surveys for which the microdata (unit-record data) are in the public domain; second, 78 standardised multicountry surveys for which results and sample size are reported but microdata were not available; third, 142 national surveys that measured immunisation coverage reported in the WHO and UNICEF vaccine coverage

Results

We provide DTP3 crude coverage estimates from analysed survey, reported survey (with and without sample sizes), and administrative data for 193 countries in webappendix 5. Figure 1 shows twelve examples of DTP3 crude coverage estimates from surveys, administrative data as well as countries' official estimates reported to WHO. These examples are intended to emphasise the importance of country by country assessment and to highlight patterns in the data; they are not intended to be representative

Discussion

Our systematic analysis shows that the crude coverage of DTP3 immunisation based on surveys has not progressed to the level suggested by countries' official reports or the WHO and UNICEF estimates. Furthermore, the way in which improvements in coverage have been achieved is far more gradual than suggested by officially reported estimates, or the WHO and UNICEF estimates. This gradual improvement probably indicates the investments and time needed to build the necessary infrastructure such as

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