The IMG was given a clear mandate in objective 2: introduce ≥1 dose of IPV in countries using only OPV by end of 2015, withdraw all tOPV in 2016 and introduce bOPV, and strengthen RI programs in focus countries (Afghanistan, Angola, Chad, Democratic Republic of the Congo, Ethiopia, India, Nigeria, Pakistan, Somalia, and South Sudan). These goals, with their stated (although extremely ambitious) timelines, gave the IMG’s work a clear sense of purpose as well as a sense of urgency. Close to 190 persons were involved in the work of the IMG and its subgroups, as well as thousands in countries around the world who were working on IPV introduction, the switch, and RI; ensuring that everyone was fully informed and moving in the same direction was critical. The IMG relied on the strengths of each organization to implement the activities and left the policy making to bodies such as SAGE. Its efforts focused on coordinating activities to meet a set of specific and agreed-on goals at global, regional, and country levels.

Having the WHO EPI Coordinator and the Chief of Immunization at UNICEF as cochairs of the IMG gave the work legitimacy, facilitating buy-in at all levels of their organizations. In addition, their positions within their respective agencies meant they had already developed strong networks across both their own and partner organizations, on which they were able to draw to build support for and engagement in the IMG’s work and mandate. The cochairs’ relatively senior roles within their own organizations gave them direct access to the necessary policy makers and leaders within the broader immunization community, as well as the ability to mobilize their own staff to support the work.

Perhaps most critically, the cochairs worked in partnership, supported by a dedicated secretariat at WHO along with surge support from the Task Force for Global Health. The cochairs regularly put the work of the IMG above politics and found ways to use each IMG partner agency for its respective strengths, helping to mitigate each other’s weaknesses.

At global level, high-level commitment was critical to mobilizing countries; joint letters were sent to ministers of health from the Director-General of WHO, the Executive Director of UNICEF, and the Chief Executive Officer of Gavi, as appropriate, to all OPV-only countries to encourage IPV introduction within the timelines. The WHO Director-General and UNICEF Executive Director sent a second joint letter to highlight the importance of meeting switch timelines. This level of collaboration and leadership, which was matched at regional and country levels, cannot be overstated and is described in further detail below.

The time-bound nature of the Endgame served as a motivator for all those involved. Strong leadership at all levels led to the proactive identification of problems, flexibility to think out of the box to find solutions when needed, and the ability to advocate for the resources needed to implement activities under tight timelines.

From the outset, the IMG sought to work in collaborative, open, and transparent ways. The responsibility of chairing the five IMG subgroups was divided up among the IMG partners, which helped build an inclusive team atmosphere and accountability at all levels.

Regional colleagues were invited to join all IMG meetings and subgroup calls. Discussions were summarized and circulated broadly. Interested partners such as the Clinton Health Access Initiative, Agence de Médicine Préventive, John Snow International, the Program for Appropriate Technology in Health, and WHO’s Immunization Practices Advisory Committee were invited to participate in IMG subgroups and contribute their skills and expertise in specific areas. This inclusive approach was critical, especially in the area of IPV introduction, where the timelines were extremely tight.

The IMG also engaged in regular dialogue with IPV and OPV manufacturers and the national regulatory agencies with oversight of production facilities to ensure that they too were working toward the same goals, ensuring full transparency on program objectives. This dialogue was critical to ensuring the available IPV was allocated in line with program priorities, particularly because the global IPV supply became increasingly constrained from 2014 onward owing to setbacks manufacturers encountered in scaling up production and rising demand for IPV use in mass vaccination campaigns [2].

The IMG recognized early on that with 126 countries involved in IPV introduction and at least 155 countries and territories that would need to be involved with tOPV withdrawal, leadership by regional colleagues, particularly from WHO and UNICEF, was critical. The IMG relied heavily on their guidance and input in developing its work plan.

Regional offices led the activities for their respective regions, with the IMG—working largely through the implementation subgroup—providing support as requested. This support took a different form for each region, based on their specific needs. Recognizing the heavy burden this work placed on regions, UNICEF and WHO regional offices were offered resources to help augment their human resource capacity. This augmentation was tailored to each region and included seconded staff recruited by the Task Force for Global Health, creation of short-term technical officer posts, and hiring of consultants. Collaboration across WHO and UNICEF regional offices was also key. The IMG established a process by which its budget for activities was divided across WHO and UNICEF, and the agencies thus worked in partnership to develop their annual plans and support countries, avoiding duplication of efforts. Regional participation in regular calls with the various IMG subgroups provided an opportunity to track regional progress, proactively identify any issues of concern, and provide support as needed.

Given the extremely ambitious timelines laid out in the Endgame, and the need for a large number of countries to implement activities in a synchronized manner, the IMG recognized that active country leadership and cooperation would be critical, and that exceptional targeted financial and staffing support would need to be provided to certain countries.

The IMG began engaging immunization staff at the country level from the outset, and in particular encouraged engagement with national immunization technical advisory groups to support decision making on IPV introduction. Given the ambitious Endgame timelines, countries eligible for and graduating from Gavi support had been offered support committed by donors to the Endgame but implemented by Gavi for IPV introduction. However, the IMG recognized that for many middle-income countries. which were not eligible for Gavi funding, catalytic support would be necessary to ensure that they would be able to introduce IPV by the Endgame targets, although such middle-income countries would then take over the financing responsibility after this initial support. The IMG advocated with the POB and received approval to provide support to these countries. Likewise, to ensure that all 155 countries and territories executed the global withdrawal of OPV type 2 in a synchronized manner, the IMG recognized that financial support would need to be extended on a limited basis to these countries, which the POB approved [3].

The IMG’s commitment to meet country needs went beyond the financial sphere. The IMG’s implementation subgroup, together with WHO and UNICEF regional offices, and the support of the Task Force for Global Health, organized trainings to ensure that a cadre of trained consultants were ready to support countries as needed.

To focus its efforts and resources efficiently, the IMG operated using a risk-based prioritization approach in which countries were divided into tiers based on the assessed risks for outbreaks of polio caused by type 2 circulating vaccine-derived polioviruses they would face once OPV type 2 was withdrawn (Table 1) [3]. All IMG partners as well as SAGE endorsed this approach and the tier criteria. The IMG’s supply working group used this risk-based approach to allocate IPV, and the IMG itself used it to prioritize technical assistance when needed, as well as to identify countries for financial support.

Key to the IMG’s success was its willingness to be flexible and adapt to consistently changing situations. For example, the Gavi Secretariat leveraged its existing business model, which GPEI donors were already comfortable with, to help encourage rapid release of funds for IPV procurement and technical assistance. In addition, the Gavi Secretariat developed a new expedited process for countries to apply for IPV introduction support, which included the waiving of its standard requirements, such as cofinancing and minimum coverage thresholds. WHO organized regional workshops of national regulatory authorities to streamline the licensing of IPV and bOPV and prioritized the review of prequalification dossiers to ensure that vaccine supply could be available as soon as possible.

When it became clear in mid-2014 that the available IPV supply would be insufficient to meet demand, WHO convened special scientific committees and launched studies to explore the feasibility of safely implementing measures to stretch existing supply (eg, increasing the length of time that an open vial of IPV could be safely used, fractional dosing of IPV delivered intradermally). At the Centers for Disease Control and Prevention, funds and personnel were made available on short notice to conduct several studies regarding health care providers’ and child caregivers’ acceptance of the administration of multiple injectable vaccines at a single visit [5], a key concern around adding IPV to the RI schedules in many countries. At UNICEF, new positions were fast-tracked for creation at regional levels to ensure adequate support for IPV introduction. The Bill & Melinda Gates Foundation secured the involvement of the Task Force for Global Health to provide surge support to IMG activities rapidly as needed.

Equally important as this flexibility was the IMG’s ability to adapt to changing situations and to have all partners on the same page when doing so. This included procedural issues, such as updating the format of IMG monthly progress reports as the focus of the IMG’s work changed and merging or splitting subgroups when relevant and hibernating subgroups that had completed their tasks—for example, hibernating the finance group once budgeting was completed, or creating a working group on IPV supply as part of the implementation group to closely monitor and allocate the available vaccine.

The IMG’s flexibility was also seen when dealing with technical issues, such as IPV supply. While the IMG partners, particularly UNICEF’s Supply Division, worked hard to get accurate projections of vaccine availability, several consecutive reductions in IPV supply continued to haunt the program as demand continued to firm up. All partners agreed to use the risk-based tiering system to prioritize supply of IPV to those countries most in need. Associated decisions were made jointly and communicated in a single voice to affected countries, with a focus on moving forward in the most efficient and effective way whenever new situations or issues emerged.

The IMG used existing tools where possible, for example, with its approach to strengthen RI in the 10 focus countries [6]. Rather than introduce a new process, the IMG and its RI subgroup engaged in ongoing efforts to develop a single annual plan to guide immunization activities and provided catalytic funding for specific priority activities identified by each country, rather than for a preset activity defined by the IMG.

The IMG had dual reporting lines to SAGE and to the POB through the Strategy Committee. The IMG benefitted from the engagement of these high-level bodies, from both the immunization and the polio sides. SAGE was responsible for the policies regarding IPV introduction and approving the timelines for the switch from tOPV to bOPV. Given that SAGE is the main policy-making body within the global immunization community, its endorsement of relevant objective 2–related policies was a critical step to enabling widespread country implementation under very tight timelines.

Because the POB is made up of the heads of each GPEI partner agency, it yielded significant influence. Providing regular updates to the POB and seeking its concurrence with the IMG’s proposed directions ensured high-level engagement and support within each organization. The IMG used its interactions with the POB to highlight areas of concern and seek POB interventions to unblock obstacles as needed. POB’s political advocacy and interventions were key factors in securing country-level commitment, and their support of the IMG’s financial requests, and the funds that came with that support, was essential for countries to meet the Endgame timelines.

Providing regular, clear updates to all partners was a priority for the IMG and was seen as critical for ensuring broad engagement and commitment to the work on objective 2. Throughout the IMG’s work, regular communications (eg, information notes, job aids, training materials, and predeveloped PowerPoint presentations) were developed and disseminated for use by the communications subgroup. The IMG produced both scientific information packages as well as simple, clear documents that would be useful to frontline health care workers. These documents, which were translated into French, and often Spanish, Russian, and Arabic, allowed the IMG to keep regions, countries, and partners up to date as new information became available or situations changed. Early on, the IMG agreed to develop a Web site, hosted by WHO’s immunization program, where all information on objective 2 could be accessed publicly. This Web site was updated regularly and became a critical tool for the IMG (http://www.who.int/immunization/diseases/poliomyelitis/endgame_objective2/en/, accessed 7 October 2016).

In addition to producing materials, the IMG and regional offices also prioritized including sessions on IPV introduction and the tOPV-bOPV switch at key meetings of EPI managers, and when needed, organizing separate objective 2 focused meetings. These meetings ensured that countries’ senior immunization staff understood the rationale for objective 2 and had access to the latest information. IMG members from all partner agencies regularly attended a variety of meetings at regional and global levels to give updates and answer questions. The IMG, with the support of the Task Force for Global Health, also organized a series of Web-based seminars on key topics to reach partners and colleagues in an interactive, efficient, and widespread manner.

With the support of the Task Force for Global Health, the IMG developed a detailed annual work plan, which was updated and reviewed monthly. This was a critical tool to ensuring that all critical activities were completed on time and that any potential delays were identified in advance, so that the IMG could explore ways to mitigate the delay and/or its impact. This common work plan allowed all partners and IMG members to monitor and get updates on IMG activities. The IMG also maintained a dedicated section of the WHO’s Immunization Repository that tracked country progress toward IPV introduction and the switch. Updated regularly by regions and headquarters staff, the repository provided a single resource from which all IMG partners could get up to date information on IPV introduction and OPV withdrawal in each country. A report was generated monthly and reviewed on the IMG call to reflect progress. While time consuming, these activities were critical to the IMG staying on track and flagging potential challenges and problems before they escalated.