How to Strengthen Vaccination for Measles and Other Infectious Diseases? Lessons from Smallpox Eradication and Polio-Free Efforts
"The most important legacy of smallpox eradication was its demonstration of how many people could be protected through vaccination, so rapidly and inexpensively with a well planned program and quality-control monitoring."
—D.A. Henderson, WHO interview (2008)
Introduction
The significant measles outbreaks in Texas and New Mexico, which have infected more than 250 people and claimed two lives; a flu season that led to record numbers of hospitalizations; and the potential for a bird flu epidemic in the United States (U.S), are a stark reminder of the persistent threat posed by infectious diseases. It underscores the "clear and present danger" these diseases pose when not prevented and controlled effectively. The COVID-19 pandemic vividly demonstrated how the unchecked spread of infectious pathogens can disrupt lives, destabilize societies, and impose significant human, social, and economic costs.
In a fascinating book “Pathogenesis: A History of the World in Eight Plagues”, Jonathan Kennedy explores how infectious diseases have shaped our history, from the Paleolithic era to COVID-19, contributing to human evolution and the rise and fall of civilizations. As public health crises have repeatedly challenged societies, it is crucial to draw on lessons learned from past experiences to effectively respond to emerging and future infectious threats. By applying this knowledge, we can strengthen health systems, enhance resilience, and better safeguard communities against present and future public health risks.
Some of us have been blessed for having been exposed during our formative years to historical public health leaders such as Prof. D.H. Henderson, who led at the World Health Organization (WHO) the international effort to eradicate smallpox worldwide, before becoming the dean of the Johns Hopkins Bloomberg School of Public Health, and Dr. Ciro de Quadros, a Brazilian epidemiologist who was part of the smallpox eradication effort in Ethiopia and later led the Pan American Health Organization (PAHO)-driven polio-free initiative in the Americas.
As discussed in this post, the implementation and lasting impact of these international efforts provide valuable insights for the prevention and control of infectious diseases today through well-organized and effectively managed immunization programs, which are essential components of a resilient health system.
The Power of Immunization: Protecting Lives Through Vaccination
Immunization is the process of making an individual resistant to a specific disease, typically through the administration of a vaccine. Vaccines work by stimulating the body’s immune system, enabling it to recognize and fight off infections more effectively.
By preventing the onset of vaccine-preventable diseases (VPDs), immunization plays a crucial role in reducing illnesses, disabilities, and deaths worldwide. It protects against a wide range of serious diseases, including cervical cancer, poliomyelitis, measles, rubella, mumps, diphtheria, tetanus, pertussis (whooping cough), hepatitis A and B, bacterial pneumonia, rotavirus-related diarrheal diseases, and bacterial meningitis.
As a cornerstone of public health, immunization helps safeguard communities, reduce healthcare burdens, and improve overall quality of life.
Lessons from the Eradication of Smallpox
Smallpox was once a feared infectious disease caused by the variola virus. It was a severe and often fatal disease. Characterized by fever and a distinctive, progressive skin rash, it had a mortality rate of about 30%, with higher rates among infants. Survivors were often left with permanent scars and, in some cases, blindness.
More than 40 years have passed since the last naturally occurring case of smallpox, marking the “death of a disease.” The global eradication of smallpox, which stands as one of the most significant achievements in public health, was the result of a 10-year smallpox eradication plan approved in 1966 by the World Health Assembly. It built upon the failed efforts over 1957-1975 to eradicate hookworm, yellow fever, yaws, and malaria.
The plan included two components: (i) systematic vaccination; and (ii) a new concept—surveillance and containment. First, it called for continuous, routine collection of data about cases and deaths due to infectious diseases; the regular analysis and interpretation of this information; and its regular distribution to those responsible for disease control. Second, the containment of outbreaks by special containment teams required that vaccines be administered in the area where outbreaks were occurring, to break the chain of transmission by vaccinating possible contacts in areas where there were cases.
As explained by Prof. D.H. Henderson in an interview, an interesting historical aspect of this effort was that the plan was approved during the time that the Cold War between the U.S and the Soviet Union was at its peak. Both superpowers put aside their political differences to support and fund the smallpox eradication campaign, highlighting the critical importance of global cooperation and solidarity.
Indeed, a key lesson from this experience in effectively addressing the threat of emerging and reemerging infectious diseases worldwide is the necessity for all countries to collaborate, co-fund, and actively participate in a global effort to control the spread of infectious pathogens that do not respect national boundaries.
There are three additional lessons that can be derived from the smallpox eradication experience, as recently highlighted in a Lancet commentary:
Well-defined, time-bound, programs need to be prepared and adopted, with clear, measurable objectives for extinguishing community transmission.
Equitable access and distribution of vaccines among countries, ramping up vaccine production, and ensuring quality control of laboratories making the vaccines.
Key actions include:
Conducting country vaccination readiness assessments to identify gaps in the system to inform policy and programmatic decisions.
Allocating adequate financial resources for strengthening logistical and operational capacity, including cold chain systems, to vaccinate entire populations in accordance with the results of the readiness assessments.
Having a cadre of well-trained personnel to administer the vaccines.
Involving local communities; and,
Supporting continuous research and feedback in the field.
Through extensive vaccination campaigns and surveillance, the World Health Organization (WHO) certified the eradication of smallpox in 1980, with the last naturally occurring case reported in 1977. This success was largely due to the development and widespread administration of effective vaccines.
Lessons from the Polio-Free Effort in the Americas
PAHO, the Regional Office of the WHO for the Americas, has been at the forefront of immunization activity since its creation in 1902. In 1977, PAHO embarked on its Expanded Program on Immunization (EPI) which initially targeted 6 diseases: tuberculosis, diphtheria, tetanus, pertussis, polio, and measles. As national immunization programs were created, a regional revolving fund was established to ensure the sustained supply of quality vaccines at negotiated prices.
In 1985, PAHO set the goal of eradicating polio in the Americas by 1990, despite skepticism from public health experts. The success of smallpox eradication demonstrated that eliminating an infectious disease was possible. By that time, polio incidence had declined significantly, with reported cases dropping from 19 to 11 countries. Additionally, polio vaccine coverage had reached record levels across many countries, further supporting the feasibility of eradication.
Polio (Poliomyelitis), a highly infectious viral disease caused by the poliovirus, primarily affected the central nervous system of young children causing acute flaccid paralysis. Although most infections were asymptomatic, in 1 in 200 cases, the virus caused permanent paralysis in the legs or arms. The poliovirus does not respect borders and can find groups of unvaccinated or under-immunized children, which could lead to outbreaks.
In the Americas, Cuba provided early evidence that polio eradication was possible in the region. In 1962, the country launched a nationwide polio vaccination campaign using the oral polio vaccine (OPV) as part of a comprehensive elimination program. Targeting children aged 1 month to 14 years, the campaign administered two doses four weeks apart, twice a year. High vaccination coverage was achieved through intensive week-long drives, active surveillance of suspected cases, and outbreak investigations when necessary. This strategy successfully halted polio transmission, with the last recorded case in May 1962.
Interrupting wild poliovirus transmission in the Americas was carried out following PAHO’s EPI guidelines, not run as an independent initiative but as part of an effort to integrate all country programs for vaccine-preventable diseases. As such, national polio campaigns included other vaccines, such as measles, DPT, and tetanus toxoid.
The last confirmed case of poliomyelitis caused by wild poliovirus in the Americas occurred in Peru on August 23, 1991. On September 29, 1994, the International Commission for the Certification of Poliomyelitis Eradication officially declared the Americas polio-free, making the Americas the first WHO region to be certified polio-free. This historical public health achievement was the product of work led by Dr. Ciro de Quadros between 1970 and 2002, serving as PAHO's first head of the EPI.
The essential elements of the polio-free effort in the Americas, that are relevant for vaccination efforts nowadays, include:
At the country level:
Political will, local alliances, and community involvement were key to take on the goal of interrupting/controlling disease transmission. In the Americas, the regional campaign against polio was spearheaded by governments, international organizations, and nonprofits. As observed by Sir George Alleyne, the Director Emeritus of PAHO, the region became the first to defeat the once lethal childhood infection and has been able to sustain its infectious disease control programs since, because the countries in the region recognized the necessity of eradicating polio and other infectious diseases and demonstrated a strong commitment to tackling these health issues together through a coordinated Pan-American effort.
Inter-agency, interinstitutional, and intersectoral cooperation arrangements that had been developed by prior health programs, were reorganized, repurposed, and applied on a broader scale for polio eradication. An Inter-agency Coordinating Committee (ICC) was established at the regional level, to help organize the specific commitments of various members. The ICC included representatives from PAHO, UNICEF, US Agency for International Development, Inter-American Development Bank, Rotary International, and the Canadian Public Health Association. Many countries followed suit, establishing national ICCs to organize efforts at the national level. These institutional arrangements helped mobilize necessary support and the commitment of all actors involved and played an important role in mobilizing additional resources to complement existing resources at Ministries of Health. In addition to outside financial and technical resources, communities, organized community groups, and private voluntary organizations (e.g., Rotary International, religious groups, and mass media organizations) were leveraged to collaborate toward the goal. They assisted in promotional activities and distribution of supplies and provided personnel for vaccination activities.
In large measure, however, the success was due to the widespread support of local communities. For instance, in El Salvador, at the height of the country’s civil conflict in the mid-1980s, it was necessary that agreements be negotiated between the government and guerrilla forces, a painstaking process that involved PAHO, UNICEF, the Red Cross, and the Catholic Church, to observe cease-fires during national immunization days. Extraordinary social mobilization efforts accompanied the immunization campaigns, as well. Radio and television announcements and newspaper articles highlighted the importance of immunization, and people throughout Central America responded positively to these massive media campaigns.
The Plan of Action spearheaded by PAHO emphasized personnel training as a critical component of the program’s success. PAHO prepared training manuals and materials, and assisted countries with customizing these to fit the local context and circumstances. Training activities also bolstered the commitment of health workers and national governments towards the regional goal of polio eradication.
High coverage, active surveillance, and lab networks were essential components for controlling disease outbreaks. A key component of this effort was acute flaccid paralysis (AFP) surveillance, which involved thorough case investigations and stool sample testing for wild poliovirus. Enhanced surveillance was vital for the success of this initiative, as inaccurate surveillance can hinder the timely implementation of early control measures.
A reporting system with standard procedures and definitions was implemented to ensure that no cases were missed. Moreover, every case was regarded as a public health emergency and investigated immediately; its chain of transmission was used to determine the extent of virus circulation in the community.
Increased laboratory support was critical since with the decrease in the number of cases and the increase in vaccination coverage, it became more important to determine if a poliovirus isolate was a wild virus. Gaps in the logistics required for collecting specimens and transporting them from the field to the laboratory were addressed. Laboratory support networks were created to analyze stool samples, and reference laboratories were established to provide more sophisticated tests, including genetic characterization of poliovirus isolates. PAHO immediately notified all countries of any outbreaks in the Americas so that traveler’s advisories could be issued.
Conducting vaccination campaigns simultaneously and within a short period of time was beneficial to keep the momentum going, both for logistical and for immunity reasons. The main strategy for interrupting wild poliovirus transmission in the Americas was the implementation of National Immunization Days (NIDs) twice a year, targeting children less than 5 years of age with one dose of trivalent oral poliovirus vaccine (tOPV). This strategy was gradually replaced by regular immunization services performed routinely by health services.
At Global and Regional levels:
Addressing public health emergencies of international concern requires international cooperation and coordinated support to mobilize resources and technical assistance for national response efforts. International organizations such as the World Health Organization (WHO) played a critical role in advising and supporting national governments while ensuring sustained disease containment measures.
Aligned with the 2021 PAHO resolution "Reinvigorating Immunization as a Public Good for Universal Health," the Special Program Comprehensive Immunization (CIM) is now contributing to revitalize immunization programs in Member States in the Americas by implementing innovative strategies across six key areas:
Strengthening governance, leadership, and financing of immunization programs.
Enhancing immunization coverage monitoring and surveillance through digital intelligence.
Integrating immunization into primary health care systems for universal health access.
Developing strategic communication to foster social awareness, trust in vaccines, and service accessibility.
Building human resource capacities for immunization programs.
Leveraging scientific evidence for informed decision-making and program effectiveness.
These efforts seek to ensure equitable and sustained immunization coverage across the region.
Moving Forward: Building Upon Lessons Learned
The eradication of smallpox and the polio-free outcome in the Americas provide valuable lessons for the prevention and control of infectious diseases. As discussed above, success in these efforts was driven by clear goals, coordinated action, adaptability, and sustained commitment at all levels—from global organizations to local communities.
As Dr. Ciro de Quadros emphasized in an interview, collaboration across sectors is essential. Public health programs must remain flexible, responding to emerging challenges while maintaining a strategic focus. Crucially, mobilizing communities, integrating data-driven decision-making, and ensuring vaccine accessibility go beyond medical interventions; they require political will, logistical planning, and social engagement. Investments in robust health infrastructure and workforce training are fundamental to sustaining immunization efforts and preventing disease resurgence.
Integrated Approaches for Disease Control
A holistic approach to disease control strengthens public health responses. While targeted (vertical) programs focus on specific diseases and broad (horizontal) programs aim to improve healthcare systems, a diagonal approach—embedding disease-specific initiatives within broader health system improvements—has proven most effective. Integrating vaccination programs with maternal and child health services increases efficiency and expands coverage, while disease surveillance systems enhance broader public health monitoring.
Long-term success depends on political stability, sustained financial commitments and allocations, and strategic investments in healthcare infrastructure, ensuring that eradication efforts contribute to resilient systems capable of addressing future outbreaks.
From Planning to Action: Core Vaccination Strategies
1. Planning & Management
Effective vaccination programs require meticulous planning, accountability, and coordination across sectors. Governments and health authorities must establish oversight mechanisms, utilize real-time data to monitor vaccine distribution, and ensure sustainable financing. Risk assessments help identify potential bottlenecks, allowing for contingency planning. Additionally, training healthcare workers enhances their capacity to administer vaccines, engage with communities, and address logistical challenges.
2. Supply & Distribution
An efficient supply chain is crucial for equitable vaccine access. Reliable procurement processes prevent shortages and wastage, while a well-maintained cold chain system preserves vaccine efficacy. Efficient logistics and transportation networks ensure timely delivery, even in remote areas, while prioritization strategies focus on high-risk populations. Collaborations with the private sector enhance distribution efficiency, leveraging expertise in supply chain management. Safe disposal of medical waste and infection control measures in health facilities following evidence-based protocols and guidance further support the safety and quality of immunization programs.
3. Community Engagement & Advocacy
Demand and uptake of vaccines is of upmost importance for vaccinating entire populations. Building public trust in vaccination efforts requires proactive communication and advocacy. Thus, sustained social mobilization to bring society together to trust and accept a new vaccine is an indispensable action. Misinformation must be countered through transparent, evidence-based messaging. Non-partisan actors must be engaged to communicate with the public about the vaccine to address disinformation head-on.
The polio vaccination experience in the United States, for example, evidenced that transparency, independence, and trust of “outside” organizations such as The March of Dimes helped overcome vaccine hesitancy. Also, the use of public figures, such as the singer Elvis Presley (the King of Rock ‘n’ Roll) getting one of the first shots of the polio vaccine on the TV set of the “The Ed Sullivan Show” in October 1956, inspired reluctant U.S. teens to get inoculated.
In the conflict-riven Central America of the 1980s, the PAHO’s “Health as a Bridge for Peace” initiative, not only helped achieve one-day cease fires among combatants that were negotiated for polio vaccination, but supported the extraordinary social mobilization efforts that accompanied the immunization campaigns, as health workers at all levels sought to convince the population to take their children to health posts and special vaccination sites to be vaccinated.
These lessons are of relevance nowadays given skepticism and distrust of governments in many countries globally. Public awareness campaigns not only increase vaccine acceptance but also help manage expectations regarding availability of vaccine supplies and prioritization in the administration of vaccines.
4. Vaccine Safety & Surveillance
Post-marketing surveillance plays a critical role in assessing vaccine safety and effectiveness. Clinical trials provide initial evidence, but real-world monitoring is necessary to understand vaccine performance across diverse populations. Healthcare providers must report adverse events through pharmacovigilance systems, while electronic health records and national databases enhance tracking efforts. Strong data infrastructure supports outbreak investigations, ensures transparency, and builds confidence in immunization programs.
Diagnostic systems complement vaccine surveillance by monitoring immunity levels, assessing vaccine effectiveness, and identifying coverage gaps. National testing strategies must evolve with emerging technologies, ensuring healthcare personnel are trained in proper infection control measures. Standardized testing procedures and biosafety protocols are essential for accurate diagnostics and safe specimen handling.
Pharmacovigilance or the monitoring of the safety in the use of vaccines and other medicines can also support risk communication—the delivery of effective information, education, and communication by government officials, service providers, and pharmaceutical firms to the public. As shown during the COVID-19 pandemic, these activities are vital to address disinformation that hampers public health efforts, concerns and fears among the public about adverse effects of medicines, and ultimately, to save lives.
Conclusion
By applying these lessons, public health programs can strengthen immunization efforts while fortifying healthcare systems against future threats. Disease eradication is not just about eliminating a single pathogen—it is about building resilient health systems capable of responding to evolving global health challenges.
