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One Health interventions that address human, animal, and environmental health domains are critical for controlling the global challenge of antimicrobial resistance (AMR). These interventions can target upstream conditions, such as prevention strategies like vaccination or policies, to restrict antimicrobial use in humans, animals, and plants, with a goal to reduce the selective pressure that can drive the emergence and expansion of drug-resistant pathogens. Downstream, environmental hygiene initiatives can target transmission pathways between people and animals to limit exposure to drug-resistant pathogens. Holistic, transdisciplinary approaches that address the factors driving antimicrobial use in people, animals, and the environment hold promise to help curb the global challenge of AMR.

There are 1 billion migrants in the world today, which means that one in seven of the world’s population are migrants. Of these, 272 million are international migrants and 763 million are internal migrants. It is estimated that around 70 million of the world’s migrants, both internal and international, have been forcibly displaced. Many things force people to leave their homes in search of a better future: war, poverty, persecution, climate change, desertification, urbanization, globalization, inequality, and lack of job prospects. Migrants remain among the most vulnerable members of society even when their living conditions improve after migration. Migrant women and children are a particularly vulnerable group and have a great need for basic and preventive health care. Many refugees and migrants are young and in good health, but hard living conditions and difficulty accessing basic health care can affect their state of health. Many of them face inhuman journeys during migration and live in refugee camps with very low standards of hygiene; when they find a job, they are often exploited. All these things can also affect their mental health. Migrants struggle with similar challenges as other marginalized groups when it comes to access to health care, but they face the additional barriers of mobility, language barriers, cultural differences, lack of familiarity with local health care services, and limited eligibility for publicly and privately funded health care. Governments should provide affordable preventive and basic health care to refugees and migrants not only because it is a human right but also because in the long term it can lower the costs of the whole health care system.

From the first vaccine (cowpox, developed by Edward Jenner in 1796), more than 100 years elapsed before additional vaccines for broad population use (diphtheria toxoid, tetanus toxoid, and whole cell pertussis) became available between 1920 and 1940. Then followed inactivated polio vaccine in the 1950s, and live attenuated vaccines for measles, mumps, rubella, and polio in the 1960s. In 1979, global elimination of smallpox was formally certified, with the last human case occurring in Somalia, almost 200 years after Jenner administered cowpox vaccine to James Phipps. In 2019, global elimination is tantalizingly close for maternal and neonatal tetanus and polio. Despite recent outbreaks, elimination has also been achieved at country and regional levels for measles and rubella and, if achieved globally, will offer, as it has for smallpox, large reductions in child mortality and morbidity and in health system costs. Short of elimination, it is important to define the public health impact of vaccines broadly and at the population level. These broader impacts include benefits to families flowing from prevention of long-term sequelae of infection in children, and to populations and health systems from reduced transmission of infection. Importantly, well-delivered vaccination programs will have a substantial impact by improving equality in health outcomes across populations. Broader impacts include reductions in syndromic disease beyond laboratory-proven infection (e.g., diarrhea and pneumonia), indirect reductions in disease in those not immunized (within and beyond age cohorts targeted by vaccine programs), and improvements in other health services driven by the infrastructure for vaccine delivery. Measurement of these broader impacts can be challenging and must also acknowledge the potential for trade-offs, such as replacement disease due to non-vaccine strains, as documented for pneumococcal infection. The realization of the benefits of vaccines globally for all children began with the Expanded Program on Immunization (EPI) initiated by the World Health Organization (WHO) in 1974. The EPI focused on improving coverage of six already available but grossly underutilized vaccines—diphtheria–tetanus–pertussis (DTP), polio, measles, and Bacille Calmette–Guerin (BCG). Through the EPI, estimated global coverage for 3 doses of DTP increased from around 20% to over 85%. Subsequent to the EPI, the Global Alliance for Vaccines and Immunization (GAVI), the Global Immunization Vision and Strategy (GIVS), and, most recently, the Global Vaccine Action Plan (GVAP) have aimed to improve access to additional vaccines in the poorest countries. These include Haemophilus influenzae type b (Hib), hepatitis B, pneumococcal conjugate, rotavirus, and human papillomavirus (HPV) vaccines, all introduced in high-income countries from the 1990s. In this chapter, the scope and methodological issues in measuring public health impact are reviewed, and estimates of the global public health impact of individual vaccines in children summarized, concluding with potential future benefits to global child health from expanded maternal vaccination and vaccines under development.