Repurposed Antiviral Drugs for Covid-19 - Interim WHO Solidarity Trial Results

BACKGROUND

World Health Organization expert groups recommended mortality trials of four repurposed antiviral drugs - remdesivir, hydroxychloroquine, lopinavir, and interferon beta-1a - in patients hospitalized with coronavirus disease 2019 (Covid-19).

METHODS

We randomly assigned inpatients with Covid-19 equally between one of the trial drug regimens that was locally available and open control (up to five options, four active and the local standard of care). The intention-to-treat primary analyses examined in-hospital mortality in the four pairwise comparisons of each trial drug and its control (drug available but patient assigned to the same care without that drug). Rate ratios for death were calculated with stratification according to age and status regarding mechanical ventilation at trial entry.

RESULTS

At 405 hospitals in 30 countries, 11,330 adults underwent randomization; 2750 were assigned to receive remdesivir, 954 to hydroxychloroquine, 1411 to lopinavir (without interferon), 2063 to interferon (including 651 to interferon plus lopinavir), and 4088 to no trial drug. Adherence was 94 to 96% midway through treatment, with 2 to 6% crossover. In total, 1253 deaths were reported (median day of death, day 8; interquartile range, 4 to 14). The Kaplan-Meier 28-day mortality was 11.8% (39.0% if the patient was already receiving ventilation at randomization and 9.5% otherwise). Death occurred in 301 of 2743 patients receiving remdesivir and in 303 of 2708 receiving its control (rate ratio, 0.95; 95% confidence interval [CI], 0.81 to 1.11; P = 0.50), in 104 of 947 patients receiving hydroxychloroquine and in 84 of 906 receiving its control (rate ratio, 1.19; 95% CI, 0.89 to 1.59; P = 0.23), in 148 of 1399 patients receiving lopinavir and in 146 of 1372 receiving its control (rate ratio, 1.00; 95% CI, 0.79 to 1.25; P = 0.97), and in 243 of 2050 patients receiving interferon and in 216 of 2050 receiving its control (rate ratio, 1.16; 95% CI, 0.96 to 1.39; P = 0.11). No drug definitely reduced mortality, overall or in any subgroup, or reduced initiation of ventilation or hospitalization duration.

CONCLUSIONS

These remdesivir, hydroxychloroquine, lopinavir, and interferon regimens had little or no effect on hospitalized patients with Covid-19, as indicated by overall mortality, initiation of ventilation, and duration of hospital stay. (Funded by the World Health Organization; ISRCTN Registry number, ISRCTN83971151; ClinicalTrials.gov number, NCT04315948.).

Repurposed Antiviral Drugs for Covid-19 - Interim WHO Solidarity Trial Results

BACKGROUND

World Health Organization expert groups recommended mortality trials of four repurposed antiviral drugs - remdesivir, hydroxychloroquine, lopinavir, and interferon beta-1a - in patients hospitalized with coronavirus disease 2019 (Covid-19).

METHODS

We randomly assigned inpatients with Covid-19 equally between one of the trial drug regimens that was locally available and open control (up to five options, four active and the local standard of care). The intention-to-treat primary analyses examined in-hospital mortality in the four pairwise comparisons of each trial drug and its control (drug available but patient assigned to the same care without that drug). Rate ratios for death were calculated with stratification according to age and status regarding mechanical ventilation at trial entry.

RESULTS

At 405 hospitals in 30 countries, 11,330 adults underwent randomization; 2750 were assigned to receive remdesivir, 954 to hydroxychloroquine, 1411 to lopinavir (without interferon), 2063 to interferon (including 651 to interferon plus lopinavir), and 4088 to no trial drug. Adherence was 94 to 96% midway through treatment, with 2 to 6% crossover. In total, 1253 deaths were reported (median day of death, day 8; interquartile range, 4 to 14). The Kaplan-Meier 28-day mortality was 11.8% (39.0% if the patient was already receiving ventilation at randomization and 9.5% otherwise). Death occurred in 301 of 2743 patients receiving remdesivir and in 303 of 2708 receiving its control (rate ratio, 0.95; 95% confidence interval [CI], 0.81 to 1.11; P = 0.50), in 104 of 947 patients receiving hydroxychloroquine and in 84 of 906 receiving its control (rate ratio, 1.19; 95% CI, 0.89 to 1.59; P = 0.23), in 148 of 1399 patients receiving lopinavir and in 146 of 1372 receiving its control (rate ratio, 1.00; 95% CI, 0.79 to 1.25; P = 0.97), and in 243 of 2050 patients receiving interferon and in 216 of 2050 receiving its control (rate ratio, 1.16; 95% CI, 0.96 to 1.39; P = 0.11). No drug definitely reduced mortality, overall or in any subgroup, or reduced initiation of ventilation or hospitalization duration.

CONCLUSIONS

These remdesivir, hydroxychloroquine, lopinavir, and interferon regimens had little or no effect on hospitalized patients with Covid-19, as indicated by overall mortality, initiation of ventilation, and duration of hospital stay. (Funded by the World Health Organization; ISRCTN Registry number, ISRCTN83971151; ClinicalTrials.gov number, NCT04315948.).

How can we evaluate the potential of innovative vaccine products and technologies in resource constrained settings? A total systems effectiveness (TSE) approach to decision-making

Innovations in vaccine product attributes could play an important role in addressing coverage and equity (C&E) gaps, but there is currently a poor understanding of the full system impact and trade-offs associated with investing in such technologies, both from the perspective of national immunisation programmes (NIPs) and vaccine developers. Total Systems Effectiveness (TSE) was developed as an approach to evaluate vaccines with different product attributes from a systems perspective, in order to analyse and compare the value of innovative vaccine products in different settings.

The TSE approach has been advanced over the years by various stakeholders including the Bill and Melinda Gates Foundation (BMGF), Gavi, PATH, UNICEF and WHO. WHO further developed the TSE approach to incorporate the country perspective into immunisation decision-making, in order for countries to evaluate innovative products for introduction and product switch decisions, and for vaccine development stakeholders to conduct their assessments of product value in line with country preferences. This paper describes the original TSE approach, development of the tool and processes for NIPs to apply the WHO TSE approach, and results from piloting in 12 countries across Africa, Asia and the Americas. The WHO TSE framework emerged from this piloting effort.

The WHO TSE approach has been welcomed by NIP and vaccine development stakeholders as a useful tool to evaluate trade-offs between different products. It was emphasised that the concept of “total systems effectiveness” is likely to be context-specific and that TSE is valuable in facilitating a deliberative process to articulate NIP priorities, for decisions around product choice, and for prioritising the development of future vaccine innovations.

An economic evaluation of the controlled temperature chain approach for vaccine logistics: evidence from a study conducted during a meningitis A vaccine campaign in Togo

Introduction

A recent innovation in support of the final segment of the immunization supply chain is licensing certain vaccines for use in a controlled temperature chain (CTC), which allows excursions into ambient temperatures up to 40°C for a specific number of days immediately prior to administration. However, limited evidence exists on CTC economics to inform investments for labeling other eligible vaccines for CTC use. Using data collected during a MenAfriVac™ campaign in Togo, we estimated economic costs for vaccine logistics when using the CTC approach compared to full cold chain logistics (CCL) approach.

Methods

We conducted the study in Togo's Central Region, where two districts were using the CTC approach and two relied on a fullCCL approach during the MenAfriVac™ campaign. Data to estimate vaccine logistics costs were obtained from primary data collected using costing questionnaires and from financial cost data from campaign microplans. Costs are presented in 2014 US dollars.

Results

Average logistics costs per dose were estimated at $0.026±0.032 for facilities using a CTC and $0.029±0.054 for facilities using the fullCCL approach, but the two estimates were not statistically different. However, if the facilities without refrigerators had not used a CTC but had received daily deliveries of vaccines, the average cost per dose would have increased to $0.063 (range $0.007 to $0.33), with larger logistics cost increases occurring for facilities that were far from the district.

Conclusion

Using the CTC approach can reduce logistics costs for remote facilities without cold chain infrastructure, which is where CTC is designed to reduce logistical challenges of vaccine distribution.

Global routine vaccination coverage, 2014

The year 2014 marked the 40th anniversary of the World Health Organization’s (WHO) Expanded Program on Immunization, which was established to ensure equitable access to routine immunization services (1). Since 1974, global coverage with the four core vaccines (Bacille Calmette- Guérin vaccine [BCG; for protection against tuberculosis], diphtheria-tetanus-pertussis [DTP] vaccine, poliovirus vaccine, and measles vaccine) has increased from <5% to ≥85%, and additional vaccines have been added to the recommended schedule. Coverage with the 3rd dose of DTP vaccine (DTP3) by age 12 months is an indicator of immunization program performance because it reflects completion of the basic infant immunization schedule; coverage with other vaccines, including the 3rd dose of poliovirus vaccine (polio3); the 1st dose of measles-containing vaccine (MCV1) is also assessed. Estimated global DTP3 coverage has remained at 84%–86% since 2009, with estimated 2014 coverage at 86%. Estimated global coverage for the 2nd routine dose of measles-containing vaccine (MCV2) was 38% by age 24 months and 56% when older age groups were included, similar to levels reported in 2013 (36% and 55%, respectively). To reach and sustain high immunization coverage in all countries, adequate vaccine stock management and additional opportunities for immunization, such as through routine visits in the second year of life, are integral components to strengthening immunization programs and reducing morbidity and mortality from vaccine preventable diseases.

Outsourcing vaccine logistics to the private sector: The evidence and lessons learned from the Western Cape Province in South-Africa

With few exceptions, immunization supply chains in developing countries continue to face chronic difficulties in providing uninterrupted availability of potent vaccines up to service delivery levels, and in the most efficient manner possible. As these countries struggle to keep pace with an ever growing number of vaccines, more and more Ministries of Health are considering options of engaging the private sector to manage vaccine storage, handling and distribution on their behalf. Despite this emerging trend, there is limited evidence on the benefits or challenges of this option to improve public supply chain performance for national immunization programmes. To bridge this knowledge gap, this study aims to shed light on the value proposition of outsourcing by documenting the specific experience of the Western Cape Province of South Africa. The methodology for this review rested on conducting two key supply chain assessments which allowed juxtaposing the performance of the government managed segments of the vaccine supply chain against those managed by the private sector. In particular, measures of effective vaccine management best practice and temperature control in the cold chain were analysed. In addition, the costs of engaging the private sector were analysed to get a better understanding of the economics underpinning outsourcing vaccine logistics. The results from this analysis confirmed some of the theoretical benefits of outsourcing to the private sector. Yet, if the experience in the Western Cape can be deemed a successful one, there are several policy and practice implications that developing countries should be mindful of when considering engaging the private sector. While outsourcing can help improve the performance of the vaccine supply chain, it has the potential to do the reverse if done incorrectly. The findings and lessons learnt from the Western Cape experience can serve as a step towards understanding the role of the private sector in immunization supply chain and logistics systems for developing countries.

Optimizing energy for a 'green' vaccine supply chain

This paper describes an approach piloted in the Kasserine region of Tunisia to increase the energy efficiency of the distribution of vaccines and temperature sensitive drugs. The objectives of an approach, known as the 'net zero energy' (NZE) supply chain were demonstrated within the first year of operation. The existing distribution system was modified to store vaccines and medicines in the same buildings and to transport them according to pre-scheduled and optimized delivery circuits. Electric utility vehicles, dedicated to the integrated delivery of vaccines and medicines, improved the regularity and reliability of the supply chains. Solar energy, linked to the electricity grid at regional and district stores, supplied over 100% of consumption meeting all energy needs for storage, cooling and transportation. Significant benefits to the quality and costs of distribution were demonstrated. Supply trips were scheduled, integrated and reliable, energy consumption was reduced, the recurrent cost of electricity was eliminated and the release of carbon to the atmosphere was reduced. Although the initial capital cost of scaling up implementation of NZE remain high today, commercial forecasts predict cost reduction for solar energy and electric vehicles that may permit a step-wise implementation over the next 7-10 years. Efficiency in the use of energy and in the deployment of transport is already a critical component of distribution logistics in both private and public sectors of industrialized countries. The NZE approach has an intensified rationale in countries where energy costs threaten the maintenance of public health services in areas of low population density. In these countries where the mobility of health personnel and timely arrival of supplies is at risk, NZE has the potential to reduce energy costs and release recurrent budget to other needs of service delivery while also improving the supply chain.

Reducing the loss of vaccines from accidental freezing in the cold chain: the experience of continuous temperature monitoring in Tunisia

Accidental freezing of vaccines is a growing threat and a real risk for national immunization programs when the potency of many vaccines can be compromised if these are exposed to sub-zero temperatures in the cold chain. In Tunisia, this issue is compounded by using sub-standard domestic cold chain equipment instead of equipping the program with medical refrigerators designed specifically for storing vaccines and temperature sensitive pharmaceuticals. Against this backdrop, this paper presents the findings of a demonstration project conducted in Tunisia in 2012 that tested the impact of introducing several freeze prevention solutions to mitigate the risk of accidental freezing of vaccines. The main finding is that, despite the continued use of underperforming domestic refrigerators, continuous temperature monitoring using new technologies combined with other technological interventions significantly reduced the prevalence of accidental exposure to freezing temperatures. These improvements were noticed for cold chain storage at regional, district and health center levels, and during the transport legs that were part of the demonstration conducted in the regions of Kasserine in the South-Eastern part of Tunisia. Subsequent to introducing these freeze prevention solutions, the incidence of freeze alarms was reduced and the percent of time the temperatures dropped below the 2 °C recommended threshold. The incidence of freeze alarms at health center level was reduced by 40%. Lastly, the solutions implemented reduced risk of freezing during transport from 13.8% to 1.7%. Although the solution implemented is not optimal in the longer term because domestic refrigerators are used extensively in district stores and health centers, the risk of accidental freezing is significantly reduced by introducing the practice of continuous temperature monitoring as a standard. The management of the cold chain equipment was strengthened as a result which helps protect the potency of vaccines to the areas of most difficult access.

Projections of costs, financing, and additional resource requirements for low- and lower middle-income country immunization programs over the decade, 2011-2020

The Decade of Vaccines Global Vaccine Action Plan has outlined a set of ambitious goals to broaden the impact and reach of immunization across the globe. A projections exercise has been undertaken to assess the costs, financing availability, and additional resource requirements to achieve these goals through the delivery of vaccines against 19 diseases across 94 low- and middle-income countries for the period 2011-2020. The exercise draws upon data from existing published and unpublished global forecasts, country immunization plans, and costing studies. A combination of an ingredients-based approach and use of approximations based on past spending has been used to generate vaccine and non-vaccine delivery costs for routine programs, as well as supplementary immunization activities (SIAs). Financing projections focused primarily on support from governments and the GAVI Alliance. Cost and financing projections are presented in constant 2010 US dollars (US$). Cumulative total costs for the decade are projected to be US$57.5 billion, with 85% for routine programs and the remaining 15% for SIAs. Delivery costs account for 54% of total cumulative costs, and vaccine costs make up the remainder. A conservative estimate of total financing for immunization programs is projected to be $34.3 billion over the decade, with country governments financing 65%. These projections imply a cumulative funding gap of $23.2 billion. About 57% of the total resources required to close the funding gap are needed just to maintain existing programs and scale up other currently available vaccines (i.e., before adding in the additional costs of vaccines still in development). Efforts to mobilize additional resources, manage program costs, and establish mutual accountability between countries and development partners will all be necessary to ensure the goals of the Decade of Vaccines are achieved. Establishing or building on existing mechanisms to more comprehensively track resources and commitments for immunization will help facilitate these efforts.

Updating the evidence base on the operational costs of supplementary immunization activities for current and future accelerated disease control, elimination and eradication efforts

BACKGROUND

To achieve globally or regionally defined accelerated disease control, elimination and eradication (ADC/E/E) goals against vaccine-preventable diseases requires complementing national routine immunization programs with intensive, time-limited, and targeted Supplementary Immunization Activities (SIAs). Many global and country-level SIA costing efforts have historically relied on what are now outdated benchmark figures. Mobilizing adequate resources for successful implementation of SIAs requires updated estimates of non-vaccine costs per target population.

METHODS

This assessment updates the evidence base on the SIA operational costs through a review of literature between 1992 and 2012, and an analysis of actual expenditures from 142 SIAs conducted between 2004 and 2011 and documented in country immunization plans. These are complemented with an analysis of budgets from 31 SIAs conducted between 2006 and 2011 in order to assess the proportion of total SIA costs per person associated with various cost components. All results are presented in 2010 US dollars.

RESULTS

Existing evidence indicate that average SIA operational costs were usually less than US$0.50 per person in 2010 dollars. However, the evidence is sparse, non-standardized, and largely out of date. Average operational costs per person generated from our analysis of country immunization plans are consistently higher than published estimates, approaching US$1.00 for injectable vaccines. The results illustrate that the benchmarks often used to project needs underestimate the true costs of SIAs and the analysis suggests that SIA operational costs have been increasing over time in real terms. Our assessment also illustrates that operational costs vary across several dimensions. Variations in the actual costs of SIAs likely to reflect the extents to which economies of scale associated with campaign-based delivery can be attained, the underlying strength of the immunization program, sensitivities to the relative ease of vaccine administration (i.e. orally, or by injection), and differences in disease-specific programmatic approaches. The assessment of SIA budgets by cost component illustrates that four cost drivers make up the largest proportion of costs across all vaccines: human resources, program management, social mobilization, and vehicles and transportation. These findings suggest that SIAs leverage existing health system infrastructure, reinforcing the fact that strong routine immunization programs are an important pre-requisite for achieving ADC/E/E goals.

CONCLUSIONS

The results presented here will be useful for national and global-level actors involved in planning, budgeting, resource mobilization, and financing of SIAs in order to create more realistic assessments of resource requirements for both existing ADC/E/E efforts as well as for new vaccines that may deploy a catch-up campaign-based delivery component. However, limitations of our analysis suggest a need to conduct further research into operational costs of SIAs. Understanding the changing face of delivery costs and cost structures for SIAs will continue to be critical to avoid funding gaps and in order to improve vaccination coverage, reduce health inequities, and achieve the ADC/E/E goals many of which have been endorsed by the World Health Assembly and are included in the Decade of Vaccines Global Vaccine Action Plan.

Economic benefits of keeping vaccines at ambient temperature during mass vaccination: the case of meningitis A vaccine in Chad

OBJECTIVE

To evaluate the potential economic benefits of keeping a meningitis A vaccine at or near ambient temperature for up to 4 days during a mass vaccination campaign.

METHODS

During a 10-day mass vaccination campaign against meningitis A in three regions of Chad in 2011, the costs associated with storage and transport of the vaccine in a traditional cold chain system were evaluated. A mathematical model was used to estimate the savings that could have been achieved if the vaccine had been stored at or near ambient temperature--in a "controlled temperature" chain--at the peripheral levels of the supply chain system.

FINDINGS

The cost of the cold chain and associated logistics used in the campaign in Chad was 0.24 United States dollars (US$) per person vaccinated. In the modelled scenario for a controlled temperature chain, however, these costs dropped by 50% and were estimated to be only US$ 0.12 per person vaccinated.

CONCLUSION

The implementation of a "controlled temperature" chain at the most peripheral levels of the supply chain system--assuming no associated loss of vaccine potency, efficacy or safety--could result in major economic benefits and allow vaccine coverage to be extended in low-resource settings.

Global Immunization Vision and Strategy (GIVS): a mid-term analysis of progress in 50 countries

Within the overall framework set out in the Global Immunization Vision and Strategy (GIVS) for the period 2006-2015, over 70 countries had developed comprehensive Multi-Year Plans (cMYPs) by 2008, outlining their plans for implementing the GIVS strategies and for attaining the GIVS Goals at the midpoint in 2010 or earlier. These goals are to: (1) reach ≥90% and ≥80% vaccination coverage at national and district level, respectively; and (2) reduce measles-related mortality by 90% compared with the 2000 level. Fifty cMYPs were analysed along the four strategic areas of the GIVS: (1) protecting more people in a changing world; (2) introducing new vaccines and technologies; (3) integrating immunization, other health interventions and surveillance in the health system context; and (4) immunizing in the context of global interdependence. By 2010, all 50 countries planned to have introduced hepatitis B (HepB) vaccine, 48 the Haemophilus influenzae type B (Hib) vaccine and only a few countries had firm plans to introduce pneumococcal or rotavirus vaccines. Countries seem to be inadequately prepared in terms of cold-chain requirements to deal with the expected increases in storage that will be required for vaccines, and in making provisions to establish a corresponding surveillance system for planned new vaccine introductions. Immunization contacts are used to deliver other health interventions, especially in the countries in the World Health Organization (WHO) Africa Region. The cost for the planned immunization activities will double to U$27 per infant, of which U$5 per infant is the expected shortfall. Global Alliance for Vaccines and Immunization (GAVI) funding is becoming the largest contributor to immunization programmes.

Strategies for financial sustainability of immunization programs: a review of the strategies from 50 national immunization program financial sustainability plans

Financial sustainability plans (FSPs) were developed by over 50 of the world's poorest countries receiving funding support from the Global Alliance for Vaccines and Immunization (GAVI) to introduce new and underused vaccines, injection safety and immunization service support between 2000 and 2006. These plans were analysed with respect to the strategies selected to promote financial sustainability, allowing classification of FSP strategies in three areas: (1) mobilizing additional resources, (2) increasing the reliability of resources, and (3) improving program efficiency. Despite some country successes and the magnitude of planned financial sustainability strategies, huge funding gaps remain for these countries due to the initial underlying assumptions of the GAVI and financial sustainability plan model.

Introducing new vaccines in the poorest countries: what did we learn from the GAVI experience with financial sustainability?

This paper reviews the experience of the Global Alliance for Vaccines and Immunization (GAVI) in introducing hepatitis B and Haemophilus influenzae type b vaccines in the poorest countries, and explores how financing for immunization has changed since GAVI Fund resources were made available during its first wave of support between 2000 and 2006. The analysis of Financial Sustainability Plans in 50 countries allowed for some of the original funding assumptions of the GAVI approach to be tested against the realities in a wide set of countries, and to highlight implications for future immunization efforts. While the initial GAVI experience with financial sustainability has proved successful through the development of plans, and many countries have been able to both introduce new vaccines and mobilize additional financing for immunization, for future GAVI supported vaccine introduction, some country co-financing of these will be needed upfront for the approach to be more sustainable.

Estimating the costs of achieving the WHO-UNICEF Global Immunization Vision and Strategy, 2006-2015

OBJECTIVE

To estimate the cost of scaling up childhood immunization services required to reach the WHO-UNICEF Global Immunization Vision and Strategy (GIVS) goal of reducing mortality due to vaccine-preventable diseases by two-thirds by 2015.

METHODS

A model was developed to estimate the total cost of reaching GIVS goals by 2015 in 117 low- and lower-middle- income countries. Current spending was estimated by analysing data from country planning documents, and scale-up costs were estimated using a bottom-up, ingredients-based approach. Financial costs were estimated by country and year for reaching 90% coverage with all existing vaccines; introducing a discrete set of new vaccines (rotavirus, conjugate pneumococcal, conjugate meningococcal A and Japanese encephalitis); and conducting immunization campaigns to protect at-risk populations against polio, tetanus, measles, yellow fever and meningococcal meningitis.

FINDINGS

The 72 poorest countries of the world spent US$ 2.5 (range: US$ 1.8-4.2) billion on immunization in 2005, an increase from US$ 1.1 (range: US$ 0.9-1.6) billion in 2000. By 2015 annual immunization costs will on average increase to about US$ 4.0 (range US$ 2.9-6.7) billion. Total immunization costs for 2006-2015 are estimated at US$ 35 (range US$ 13-40) billion; of this, US$ 16.2 billion are incremental costs, comprised of US$ 5.6 billion for system scale-up and US$ 8.7 billion for vaccines; US$ 19.3 billion is required to maintain immunization programmes at 2005 levels. In all 117 low- and lower-middle-income countries, total costs for 2006-2015 are estimated at US$ 76 (range: US$ 23-110) billion, with US$ 49 billion for maintaining current systems and $27 billion for scaling-up.

CONCLUSION

In the 72 poorest countries, US$ 11-15 billion (30%-40%) of the overall resource needs are unmet if the GIVS goals are to be reached. The methods developed in this paper are approximate estimates with limitations, but provide a roadmap of financing gaps that need to be filled to scale up immunization by 2015.

Financial challenges of immunization: a look at GAVI

Securing reliable and adequate public funding for prevention services, even those that are considered highly cost effective, often presents a challenge. This has certainly been the case with childhood immunizations in developing countries. Although the traditional childhood vaccines cost relatively little, funding in poor countries is often at risk and subject to the political whims of donors and national governments. With the introduction of newer and more costly vaccines made possible under the Global Alliance for Vaccines and Immunization (GAVI), the future financial challenges have become even greater. Experience so far suggests that choosing to introduce new combination vaccines can significantly increase the costs of national immunization programmes. With this experience comes a growing concern about their affordability in the medium term and long term and a realization that, for many countries, shared financial responsibility between national governments and international donors may initially be required. This article focuses on how GAVI is addressing the challenge of sustaining adequate and reliable funding for immunizations in the poorest countries.