Child mortality has decreased substantially globally—from 12.6 million in 1990 to 6.3 million in 2013—due, in large part to of governments’ and organisations’ work, to prevent pneumonia, diarrhoea and malaria, the main causes of death in the postneonatal period. In 2012, the World Health Assembly adopted the Decade of Vaccines Global Vaccine Action Plan 2011–2020 as the current framework aimed at preventing millions of deaths through more equitable access to existing vaccines for people in all communities. The Global Alliance for Vaccines and Immunization (GAVI) plays a critical role in this effort by financing and facilitating delivery platforms for vaccines, with focused support for the achievements of improved vaccination coverage and acceleration of the uptake of WHO-recommended lifesaving new vaccines in 73 low-income countries. The GAVI Alliance has contributed substantially towards the progress of Millennium Development Goal 4 and to improving women's lives. By 2013, the GAVI Alliance had immunised 440 million additional children and averted six million future deaths from vaccine-preventable diseases in the world's poorest countries. The GAVI Alliance is on track to reducing child mortality to 68 per 1000 live births by 2015 in supported countries. This paper discusses the GAVI Alliance achievements related to Millennium Development Goal 4 and its broader contribution to improving women's lives and health systems, as well as challenges and obstacles it has faced. Additionally, it looks at challenges for the future and how it will continue its work related to reducing child mortality and improving women's health.