History of Vaccination

Vaccination is defined as the administration of antigenic material to stimulate an individual's immune system to develop adaptive immunity to a pathogen ¹. This process confers protection by engaging the body's own defenses, rather than through passive transfer of antibodies. Vaccines themselves are biological preparations that provide active acquired immunity ². They typically contain weakened or inactivated parts of a particular organism, which prime the immune system without causing the full disease ³. As a method, vaccination provides immunity against a disease, forming the cornerstone of modern preventive medicine . Together, these definitions establish the conceptual foundation for understanding how vaccines work and why they are used.⁴

The terms vaccine and vaccination derive from Variolae vaccinae, meaning smallpox of the cow ¹. This nomenclature reflects the pioneering work of Edward Jenner, who in 1796 inoculated a boy with cowpox material to protect against smallpox ⁵. Jenner called the procedure vaccination, taking the name from the Latin word for cow, vacca ⁵. His approach laid the foundation for modern vaccinology and established the principle that deliberate exposure to a related, milder agent could confer immunity ⁵. The smallpox vaccine thus became the first vaccine to be widely used, demonstrating the practical potential of this new method . These historical origins explain why the terminology remains tied to its bovine roots even as vaccination has expanded to many other diseases.⁵

Vaccination has since become a method of providing immunity against a wide range of diseases, using vaccines that contain weakened or inactivated parts of organisms ³. Over time, vaccines have been developed for many diseases, including diphtheria, tetanus, and pertussis ⁶. The development of vaccines relies on the fields of immunology and microbiology, which together inform how best to stimulate protective responses ⁷. Today, vaccination is considered one of the greatest achievements of public health, having controlled many infectious diseases and saved millions of lives worldwide . Its core definition—administering antigenic material to induce adaptive immunity—remains unchanged, even as the science behind it has advanced considerably.⁸

Long before Edward Jenner's celebrated work, a different method of protecting against smallpox was already established in parts of the world. Variolation was practiced in Asia and the Middle East in the era preceding Jenner's contributions.⁵ The practice represented an early attempt to confer protection against a disease that would later be targeted by the first true vaccine.⁵ Variolation thus occupies a distinct place in the historical record: it was not vaccination as later defined, but it was a deliberate intervention against smallpox grounded in observation and experience.⁵ Its existence demonstrates that the impulse to guard against epidemic disease long predated the scientific understanding that would eventually explain why such interventions worked.⁵

The technique of variolation was defined by its method of inoculation. It involved inoculating a person with material taken from smallpox sores.⁵ This deliberate introduction of material from the lesions of the disease was intended to induce a milder form of illness and, in turn, protection.⁵ The procedure therefore relied directly on the infectious source itself rather than on any unrelated or attenuated substitute.⁵ Because it used material from smallpox sores, variolation carried a risk that could not be eliminated. The mortality rate associated with the practice was about 1–2%.⁵

The mortality rate of about 1–2% gave variolation a hazardous character, yet it was evidently judged preferable to the full force of naturally acquired smallpox.⁵ The practice was established in Asia and the Middle East before Jenner's time, reflecting a geographically broad tradition of preventive intervention.⁵ Variolation thus stands as the pre-Jennerian precursor to vaccination, a procedure that addressed smallpox through controlled inoculation with material from smallpox sores.⁵ Its documented mortality of about 1–2% marks both its ambition and its limits, and it forms the immediate backdrop against which the later development of vaccination must be understood.⁵

Edward Jenner, an English physician, is credited with creating the first vaccine ⁵. In 1796, he inoculated an 8-year-old boy with cowpox ⁵. The first vaccine was developed against smallpox ⁴, and it was likewise for smallpox that the earliest vaccine was made ⁶. The first vaccine was developed by Edward Jenner in 1796 ³. This smallpox vaccine was the first vaccine to be widely used ⁵. Through this work, Jenner's efforts laid the foundation for modern vaccinology , establishing a precedent on which later immunization practice would rest.⁵

The significance of Jenner's achievement rests on the disease it targeted. Smallpox was an infectious disease caused by the variola virus ⁹. The first vaccine was for smallpox, a condition that would eventually become the only human disease to have been eradicated ^{6 9}. The smallpox vaccine was the first vaccine to be widely used, marking the beginning of a practice that would spread across the world ⁵. Jenner's work laid the foundation for modern vaccinology , and the smallpox vaccine stands as the earliest widely adopted product of that discipline.⁵

Jenner's contribution is understood within a longer arc of medical history. Before Jenner, variolation was practiced in Asia and the Middle East ⁵, and variolation involved inoculating a person with material from smallpox sores ⁵. As an English physician, Jenner is credited with creating the first vaccine ⁵, a step that followed these earlier practices. The first vaccine was for smallpox ⁶, and that same smallpox vaccine was the first vaccine to be widely used ⁵. In this way, his work laid the foundation for modern vaccinology and for the broader history of vaccination that followed ..⁵

Louis Pasteur developed a vaccine for rabies in 1885, an achievement that extended vaccination beyond its origins in smallpox and demonstrated that the method could be directed at a disease quite different from the one that had first inspired it ¹. Pasteur's work linked vaccination to the germ theory of disease, tying the practice of inducing immunity to a coherent account of what actually causes illness ¹. The germ theory states that many diseases are caused by microorganisms, a principle that gave vaccine development a rational foundation rather than an empirical one ¹. By connecting the two, Pasteur helped transform vaccination from a procedure into an application of a broader scientific theory ..¹

Robert Koch and Louis Pasteur were key developers of the germ theory, and their work established microorganisms as the agents of many diseases ¹. This framework supplied the reasoning behind vaccination: if a disease is caused by a microorganism, then stimulating the immune system against that organism can prevent the disease ¹. Pasteur's rabies vaccine of 1885 therefore stands as both a practical milestone and a conceptual one, since it joined the act of vaccination to the germ theory of disease ¹. The germ theory itself holds that many diseases are caused by microorganisms, a claim central to the scientific program Koch and Pasteur advanced ..¹

The convergence of Pasteur's rabies vaccine with the germ theory marked a decisive shift in the history of vaccination ¹. Pasteur linked vaccination to the germ theory of disease, while the germ theory, developed by Koch and Pasteur as key figures, held that many diseases are caused by microorganisms ¹. Together these developments gave subsequent vaccine research a theoretical basis grounded in microbiology and immunology ¹. Pasteur's 1885 rabies vaccine thus represents both a specific achievement and a broader reorientation of vaccination toward the understanding of disease causation ¹. This reorientation shaped how later vaccines would be conceived and justified ..¹

The twentieth century brought a broad expansion in the range of diseases addressed by immunization. Vaccines have been developed for many diseases, including diphtheria, tetanus, and pertussis ⁶. A combined formulation against these three infections, the DTP vaccine, was introduced in the 1940s ⁶. This period also saw the first widely used vaccine against poliomyelitis, a disease that vaccination efforts would later bring close to eradication. The first polio vaccine was developed by Jonas Salk in 1955 ³, and Albert Sabin developed an oral polio vaccine in 1961 . The shift from injected to oral administration simplified delivery of protection against polio.³

The following decades added further vaccines to routine use. The measles vaccine was introduced in 1963 ³, extending immunization programs to a highly contagious viral disease. Later in the century, the hepatitis B vaccine was first licensed in 1981 ³. The closing decades of the century also saw the licensing of a vaccine against human papillomavirus. The HPV vaccine was licensed in 2006 . Together, these introductions reflected the growing capacity of vaccine science to target distinct pathogens through different immunological strategies. Each new license broadened the catalogue of diseases that could be prevented through immunization rather than treated after onset.³

Smallpox was an infectious disease caused by the variola virus, and it occupies a unique position in the history of immunization: it is the only human disease to have been eradicated. The first vaccine ever developed was directed against smallpox, and that vaccine was also the first to be widely used. The gravity of the disease and the antiquity of efforts against it explain why smallpox became the proving ground for vaccination as a public health instrument. What began as an empirical practice would eventually be transformed into a systematic, globally coordinated undertaking whose success remains unmatched. The story of smallpox is therefore inseparable from the broader history of vaccination itself.⁹

The eradication of smallpox was achieved through a global campaign rather than through routine clinical practice alone. A defining feature of that campaign was its use of ring vaccination, a strategy that concentrated immunization around each detected case in order to interrupt chains of transmission. The last naturally occurring case was recorded in Somalia in 1977, after which transmission of the variola virus ceased. Smallpox was eradicated in 1980, and in the same year the World Health Assembly declared the disease eradicated. These milestones mark the culmination of a coordinated international effort.⁹

The significance of smallpox eradication lies not only in the elimination of a single pathogen but in the demonstration that a human disease could be removed entirely through vaccination. Smallpox remains the only human disease to have been eradicated, and no other infection has since been consigned to the same category. The campaign against it established a model of global coordination that later efforts would seek to emulate, even if none have yet matched its outcome. For the history of vaccination, smallpox thus stands as both the earliest triumph and the most complete one.⁹

The global campaign to eliminate polio represents one of the most ambitious applications of vaccination in public health history. In 1988, the World Health Organization launched the Global Polio Eradication Initiative, a coordinated effort to interrupt transmission of the virus worldwide. This initiative built on earlier achievements in vaccine development, notably the first polio vaccine developed by Jonas Salk in 1955 and the oral polio vaccine developed by Albert Sabin in 1961. Together, these vaccines provided the tools needed for widespread immunization. The launch of the initiative marked a decisive commitment by the international community to pursue the eradication of a disease through systematic vaccination.⁹

Despite decades of intensive effort, polio has not been fully eliminated. The disease remains endemic in a few countries, including Afghanistan and Pakistan, where transmission continues to pose a persistent challenge to global eradication goals. Vaccination has nearly eradicated polio, reducing its incidence dramatically from the levels seen before widespread immunization. However, the continued presence of the virus in these endemic areas demonstrates the difficulty of achieving complete interruption of transmission. The persistence of polio in these settings underscores the importance of sustained vaccination coverage to prevent outbreaks and to protect populations until eradication is finally achieved.²

The near-eradication of polio stands as a testament to the power of coordinated vaccination programs. The World Health Organization coordinates global vaccination efforts, and the Global Polio Eradication Initiative exemplifies how international collaboration can bring a disease to the brink of elimination. The hard-won progress against polio, however, remains incomplete as long as the virus circulates anywhere. The history of vaccination shows that sustained commitment, adequate coverage, and consistent surveillance are essential to finish the task. The polio campaign thus continues to serve as both a model and a cautionary tale for future eradication efforts.⁹

The closing decades of the twentieth century and the opening of the twenty-first brought notable milestones in the control of vaccine-preventable disease. Measles was declared eliminated in the United States in 2000, a status reflecting sustained immunization rather than the disappearance of the pathogen worldwide.³ The regional picture advanced further when the Americas were declared free of measles in 2016.¹⁰ Such declarations rest on the principle that vaccination coverage is key to preventing outbreaks, since immunity maintained across a population limits the transmission that would otherwise allow cases to reappear.¹⁰ These achievements illustrate how coordinated immunization programs convert individual protection into durable public health outcomes.³

The arrival of a novel coronavirus prompted an unprecedented acceleration in vaccine development. The first COVID-19 vaccines were authorized for emergency use in December 2020, less than a year after the pathogen came to global attention.³ Among the platforms deployed, mRNA vaccines use messenger RNA to instruct cells to produce a spike protein, thereby presenting the immune system with a defined target for building protective responses.³ This approach differs from the classical strategies of weakened or inactivated organisms that had long formed the basis of vaccine manufacture.³ The speed of this authorization marked a distinct moment in the long history of vaccination.⁸

These twenty-first-century developments extend a record that spans more than two centuries, throughout which vaccines have been used to control outbreaks of infectious diseases.¹ Successive milestones, from the elimination of measles in the United States to the first emergency authorizations for COVID-19 vaccines, demonstrate the continuing role of immunization in reducing the incidence of many diseases.³ Vaccination remains a central instrument of public health, and global bodies continue to coordinate the campaigns and coverage that sustain its gains.⁹ Each new platform builds upon a foundation of immunology and microbiology rather than replacing it.⁷

Global immunization is coordinated at the international level by the World Health Organization, which advances vaccination efforts across countries.⁹ A foundational step in this work came with the launch of the Expanded Programme on Immunization by the WHO in 1974.⁹ The scale of the resulting public health benefit is considerable: vaccination prevents an estimated 2-3 million deaths every year.¹⁰ This figure reflects the cumulative role of immunization in reducing the burden of infectious disease worldwide.¹⁰ The reach of these programs illustrates how organized, population-level vaccination has become a central instrument of modern public health.⁹

Guidance on the use of vaccines is provided by national public health authorities; the CDC recommends routine vaccination for children and adults.³ Such recommendations translate global and national goals into schedules that are applied in everyday clinical and community practice.³ Maintaining high levels of vaccination coverage is key to preventing outbreaks.¹⁰ Where coverage is sustained, the transmission of vaccine-preventable diseases is constrained, protecting both vaccinated individuals and the wider community.¹⁰ Coverage therefore functions as the practical measure of whether immunization programs are achieving their intended protective effect.³

The combined record of coordinated global efforts, national recommendations, and sustained coverage has established vaccination as one of the most consequential achievements in public health.⁸ Vaccines have saved millions of lives worldwide.⁷ These gains rest on the continuous application of immunization across populations, rather than on any single intervention.³ The WHO's coordinating role and the Expanded Programme on Immunization remain part of the institutional framework through which this protection is delivered.⁹

The history of vaccines spans over two centuries, a period during which vaccination has come to be considered one of the greatest achievements of public health. ⁸ The development of vaccines has led to the control of many infectious diseases, and this work relies on the disciplines of immunology and microbiology. ^{8 7} Vaccines have saved millions of lives worldwide, a measure of impact that few other interventions in medicine can claim. ⁷ The development of vaccines has been one of the most important advances in medicine, and vaccination has been used to control outbreaks of infectious diseases. ¹

Vaccines have reduced the incidence of many diseases, and they are safe and effective. ³ The reach of this record is perhaps clearest in the cases of two diseases. Vaccination has eradicated smallpox and nearly eradicated polio, an achievement that stands as the most visible demonstration of what immunization can accomplish. ² Smallpox is the only human disease to have been eradicated, a result that required a sustained global campaign. ⁹ Polio, by contrast, remains endemic in a few countries, so the near-eradication achieved so far is not yet complete. ⁹

Taken together, these outcomes underline why vaccination occupies so prominent a place in the history of medicine. The term itself reflects the field's origins in the smallpox of the cow, and the first vaccine was developed against smallpox. ^{1 4} Jenner's work laid the foundation for modern vaccinology, and the smallpox vaccine was the first vaccine to be widely used. ⁵ From that foundation, vaccines have been developed for many diseases, including diphtheria, tetanus, and pertussis. ⁶