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Luiz Augusto Cassanha Galvao, Volney Câmara, and Daniel Buss

The relationship between environment and health is part of the history of medicine and has always been important to any study of human health and to public-health interventions. In Latin America many health improvements are related to environmental interventions, such as the provision of better water and sanitation services. Latin America’s development, industrialization, and sweeping urbanization have brought many improvements to the well-being of its populations; they have also inaugurated new societies, with new patterns of consumption. The region’s basic environmental-health interventions have needed to be updated and upgraded to include disciplines such as toxicology, environmental epidemiology, environmental engineering, and many others. Multidisciplinary and inter-sector approaches are paramount to understanding new profiles of health and well-being, and to promoting effective public-health interventions. The new social, economic, labor, and consumption aspects of modern Latin American society have become more and more relevant to understanding the complex interactions in the region’s social, biological, and physical environment, which are essential to explaining some of the emerging and re-emerging public-health problems. Environmental health, as concept and as intervention, is simple and easily understood, but no longer sufficient to achieve the levels of health and well-being expected and required by these new realities. Many global changes such as climate change, biodiversity loss, and mass migrations has been identified as main cause of ill health and are at the center of the sustainable development challenges in general, and many are critical and specific public health. To face this development, other frameworks have emerged, such as planetary health and environmental and social determinants of health. Public health remains central to some, such as the improved environmental-health agenda, while others assign public health a relative position in a variety of overarching frameworks.


Silvia Declich, Maria Grazia Dente, Christina Greenaway, and Francesco Castelli

Increasing human mobility, of which migration is a component, is a key driver of microorganism circulation. Migration is a minor component of all human mobility, with most movement due to international tourism, travel for work, business, or study, and military operations abroad. Migration flows from southern low-income countries to the industrialized north have steadily increased as a consequences of a complex array of distal and proximal factors such as economic inequality, climate change, political turbulence, war and persecution, and family reunification. This has raised concerns about the potential transmission and reintroduction of microorganisms and infectious diseases into high-income host countries from migrants with asymptomatic infections such as tuberculosis, HIV, viral hepatitis, malaria, Chagas disease, and arboviral infections. These factors contribute to the mounting hostile attitude sometimes observed in receiving countries and deserve careful scientific assessment to inform policies and interventions. The available evidence does not support the hypothesis that migrants constitute a relevant infectious public health risk for the local population, although careful epidemiological surveillance is mandatory, especially where competent vectors for specific infection are present in the destination area, where certain diseases may potentially be introduced or reintroduced. The greatest risk of infectious diseases is to the migrants themselves due to increased risk of exposure within their own communities and from the burden of undetected and untreated infections caused by marginalization and poor living conditions. The health conditions vary at the different stages of settlement and interventions need to be tailored accordingly. In the early arrival phase the main health concerns are psychological, traumatic, and chronic conditions. Crowded unhygienic living conditions often experienced by migrants in reception camps coupled with low vaccination rate may facilitate the transmission of respiratory or gastrointestinal infections or vaccine-preventable diseases. After resettlement, undetected infections and the lack of access to health care due to social marginalization may lead to the reactivation or progression of infections such as tuberculosis, viral hepatitis, HIV, and chronic helminthiasis. These outcomes could be prevented through screening and treatment and would benefit both migrants and the host populations. Pretravel interventions that increase the awareness of the possible infectious risks in their countries of origin are critical to decrease travel-related infection among visiting friends and relatives, especially those traveling with children. Migrant-friendly health systems that ensure prompt access to diagnosis and treatment, regardless of legal status, are the best interventions to limit the burden and transmission of infections in this population.


Peter McIntyre and Tony Walls

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.


Eve Dubé and Noni E. MacDonald

Vaccination is one of the greatest public health successes. With sanitation and clean water, vaccines are estimated to have saved more lives over the past 100 years than any other health intervention. Vaccination not only protects the individual, but also, in many instances, provides community protection against vaccine-preventable diseases through herd immunity. To reduce the risk of vaccine-preventable diseases, vaccination programs rely upon reaching and sustaining high coverage rates, but paradoxically, because of the success of vaccination, new generations are often unaware of the risks of these serious diseases and their concerns now concentrate on the perceived risk of individual vaccines. Over the past decades, several vaccine controversies have occurred worldwide, generating concerns about vaccine adverse effects and eroding trust in health authorities, experts, and science. Gaps in vaccination coverage can, in part, be attributed to vaccine hesitancy and not just to “supply side issues” such as access to vaccination services and affordability. The concept of vaccine hesitancy is now commonly used in the discourse around vaccine acceptance. The World Health Organization defines vaccine hesitancy as “lack of acceptance of vaccines despite availability of vaccination services. Vaccine hesitancy is complex and context specific, varying across time, place and vaccines.” A vaccine-hesitant person can delay, be reluctant but still accept, or refuse one, some, or all vaccines. Technical, psychological, sociocultural, political, and economic factors can contribute to vaccine hesitancy. At the individual level, recent reviews have focused on factors associated with vaccination acceptance or refusal, identifying determinants such as fear of side effects, perceptions around health and prevention of disease and a preference for “natural” health, low perception of the efficacy and usefulness of vaccines, negative past experiences with vaccination services, and lack of awareness or knowledge about vaccination. Very few interventions have been shown to be effective in reducing vaccine hesitancy. Most of the studies have only focused on metrics of vaccine uptake and refusal to evaluate interventions aimed at enhancing vaccine acceptance, which makes it difficult to assess their potential effectiveness to address vaccine hesitancy. In addition, despite the complex nature of vaccination decision-making, the majority of public health interventions to promote vaccination are designed with the assumption that vaccine hesitancy is due to lack or inadequate knowledge about vaccines (the “knowledge-deficit” or “knowledge gap” approach). A key predictor of acceptance of a vaccine by a vaccine-hesitant person remains the recommendation for vaccination by a trusted healthcare provider. When providers communicate effectively about the value and need for vaccinations and vaccine safety, people are more confident in their decisions. However, to do this well, healthcare providers must be confident themselves about the safety, effectiveness, and importance of vaccination, and recent research has shown that a proportion of healthcare providers are vaccine-hesitant in their professional and personal lives. Effective strategies to address vaccine hesitancy among these hesitant providers have yet to be identified. A better understanding of the dynamics of the underlying determinants of vaccine hesitancy is critical for effective tailored interventions to be designed for both the public and healthcare providers.