In 1985, a measles epidemic blew through a group of Sudanese refugee camps where I was working, quickly killing scores of malnourished children and leaving a scar in my memory. More than a quarter century later, some 1.5 million children still die every year from a handful of vaccine-preventable diseases, but the discourse of death–how many children die from which disease–has shifted to a message of hope.

New partnerships, new country commitments and new donor ambition means that more vaccines are reaching more children than ever before and child mortality rates are falling throughout the world. In 30 years of work as a doctor and scientist, I am more profoundly optimistic than ever about the future of vaccines and immunization.

Immunization’s enormous strength is not just that it prevents death and is one of the most cost-effective ways to do so, but that it also prevents disease and disability. Vaccines help healthy people remain healthy, and in doing so, they remove a major obstacle to human development. In a world protected by immunization, parents can concentrate on productive work while their children go to school and live up to their full potential.

Since its establishment in 2000, the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunization) has supported developing countries to immunize an additional 325 million children, resulting in the prevention of more than five and a half million deaths.

This progress is both wonderful and relentless.

Supporting an ambitious roll out of relatively new vaccines against pneumonia and diarrhea (the two largest killers of children) since June 2011, we have supported immunization systems to reach more children than ever before. The rollout of these pneumococcal and rotavirus vaccines to some 50 countries by 2015 has started. We have also added measles-rubella and human papillomavirus (HPV) vaccines to our portfolio and worked with vaccine manufacturers to lower prices on critical vaccines.

Our 2011 to 2015 programme aims to prevent another four million vaccine-preventable deaths by supporting the immunization of an additional 240 million children in some of the world’s most marginalized populations.

This April, I visited Ghana for celebrations to mark the introduction of the pneumococcal and rotavirus vaccines that will help protect Ghanaian children from the leading causes of pneumonia and diarrhea, two diseases which together account for 20 percent of Ghana’s child mortality. Introducing even one new vaccine is a heavy lift for any country—one that includes careful planning, training and the upgrading of complex logistical and cold chain systems. Yet, through speeches, music and dancing in the sweltering west African heat, Ghana launched two vaccines and made one very cool, calm calculation: vaccines are a cost-effective intervention for reducing child mortality.

Children in Ghana and other developing countries have been dying from pneumonia and diarrhea for centuries, of course, but the pneumococcal and rotavirus vaccines only became available to them in the last two years. Why? Vaccine development and production has high fixed costs and before the GAVI Alliance, manufacturers did not see value in producing new products for developing country needs where markets were small or unstable. When the WHO, UNICEF, World Bank, Bill & Melinda Gates Foundation, vaccine manufacturers, donors, developing countries and others came together to form the GAVI Alliance, they were able to create large and predictable markets, raise money for immunization in the developing world and aggregate vaccine demand across many countries.

The GAVI Alliance spends the money it raises in the most strategic way to achieve the best results. We work to support the use of new and under-used vaccines in the 73 lowest income countries, strengthen health and immunization delivery systems, increase the sustainability of vaccine financing and help shape vaccine markets. By purchasing and procuring for 73 countries, our alliance can negotiate hard for the best deal possible. Knowing that GAVI provides large, long-term and stable markets, vaccine manufacturers can afford to drop their prices and produce new vaccines for developing countries. This public-private partnership pays dividends for the poorest children and–for the first time–provides manufacturers with extra incentive to produce more vaccines that are appropriate and affordable for the developing world. By offering such predictability, for example, GAVI’s Advance Market Commitment led to private sector investment and accelerated the production of pneumococcal vaccines for developing countries.

This terribly unequal access to markets had little to do with demand, by the way.

My wife, who until recently worked as a doctor in New York, has never seen, let alone treated a single case of measles or tetanus. In that vain, there are parents in Europe and North America who fail to realize the danger of these diseases and make the decision not to immunize their children. By contrast, in developing countries, parents will walk for hours to ensure their children are immunized—they know how quickly these diseases can steal their children.

And when the parents take their children to be vaccinated, they can also receive health advice and information about issues like family planning and HIV/AIDS.  Routine immunization serves as an access point for so many other health interventions.

GAVI’s work has accelerated production of the meningitis A, pneumococcal, rotavirus, and pentavalent vaccines to protect against a handful of deadly diseases. In the not-so-distant future, we hope to see new vaccines against Japanese encephalitis, typhoid, dengue, malaria, and even HIV. In any case, the gap is tightening between introductions in the North and introductions in the South. Nicaragua introduced the 13-valent pneumococcal vaccine in 2010, the same year that this latest generation pneumococcal vaccine was licensed for children in the United States.

Despite these successes, we still face significant obstacles when it comes to reaching more children. Many of these road blocks are technical: do countries have the capacity to deliver vaccines from central storehouses to remote clinics and to keep them cold? Are there clinics nearby or if not, outreach facilities? Do parents actually know the vaccines are available?

Yes, these technical obstacles do exist, but arguably some of the biggest barriers are political.

While 109 million children now receive routine immunization against a handful of diseases, 19.4 million still go without. Some 8.8 million of these children live in India and Nigeria. Not by coincidence, these two countries also have some of the highest child mortality rates in the world.

But both these countries have also shown a renewed appetite for vaccines.

 Once infamous for its failure with polio immunization, a real worry for global health, Nigeria has recently reiterated its commitment to tackle polio and introduced new meningitis A and pentavalent vaccines to protect its children. Meanwhile, India marked the passage this February of 12 months without a single new case of polio, reducing the number of polio endemic countries from four to three. In a country where 26.5 million children are born every year and many of them are remote, nomadic, or even unregistered, this is an impressive achievement by any measure.  Emboldened by this milestone, India is now rolling out pentavalent vaccines in a number of its states.

India’s extraordinary success brings hope that we are truly “this close” to polio eradication and that we can, in fact, reach every last child with immunization. To do this, we at GAVI are exploring both new strategies for performance-based funding and tailored approaches for fragile states and large countries where so many unimmunized children still live (and die).

The global health community has made staggering progress in the past 30 years. With new tools and news ways of working, we can do even more.