Viruela: de la primera vacuna al nacimiento del primer movimiento antivacunas / Smallpox: from the first vaccine to the birth of the first anti-vaccine movement

El último caso de viruela, la peor plaga que ha enfrentado la humanidad, fue diagnosticado hace 45 años y con él la enfermedad fue erradicada del planeta. Una hazaña épica iniciada a finales del siglo XVIII por Edward Jenner, el hombre que inoculó a su propio hijo con el pus de las lesiones de una ordeñadora que sufría viruela bovina, una enfermedad benigna antigénicamente relacionada con la viruela y que le confería inmunidad. Pocos años más tarde, en 1803, partía de España la "Real expedición filantrópica de la vacuna", llevando la vacuna a América y Asia, transportándola de brazo en brazo. A pesar del éxito de la vacuna, Jenner y la sociedad victoriana sufrieron los primeros movimientos antivacunas que hoy, en el contexto de la pandemia del COVID-19, son catapultados por los sitios de noticias falsas que socaban el conocimiento científico.

The last case of smallpox, the worst plague that humanity has faced, was diagnosed 45 years ago, marking the end of this disease in our world. It is a fascinating story that started in the late 18th century with a man called Edward Jenner. He made a name for himself by inoculating his son with the secretion of pus from the hand of a milkmaid sick with cowpox, a benign disease antigenically related to smallpox, and his inoculum conferred immunity. A few years later, in 1803, the "Royal Philanthropic Vaccine Expedition" left Spain, carrying the vaccine to the Americas and the Orient and passing the inoculum from arm to arm. Despite the vaccine's success, Jenner and Victorian society found themselves up against the first anti-vaccine backlash. In today's COVID-19 pandemic, these movements are now being super-charged by fake news websites, undermining scientific knowledge.

Life and death of smallpox.

Smallpox is an ancient scourge known since the Antiquity. It is caused by a highly contagious airborne poxvirus. This strictly human disease exists in two forms: variola major (Asian smallpox) with mortality of 20-45%, and an attenuated form called variola minor or alatrim with mortality of 1-2%, which only recently appeared in Europe and America towards the end of the 19th century. The first smallpox pandemic was the "Antonine plague", which swept through the Roman Empire in the 2nd century AD, after which smallpox became endemic in the Old World, causing seasonal and regional epidemics in Europe, affecting mostly young children until the 19th century. The discovery of the New World in 1492 and the opening of the African slave trade favored in 1518 the contamination by smallpox of the native Amerindian populations, who were massively decimated during the following centuries. In the absence of any effective treatment, preventive methods were developed from the 18th century. First, variolation was used, a dangerous procedure that consists in inoculating intradermally a small quantity of virus from convalescent patients. In the early 19th century, Edward Jenner popularized the practice of inoculating cowpox, a mild cow disease. This procedure proved to be very effective and relatively safe, leading to the decline of smallpox during the 19th century. In the 20th century, a ten-year WHO vaccination campaign led to the total eradication of smallpox in 1977. During that century, smallpox caused an estimated 300-500 million deaths worldwide. Using molecular approach, it has been discovered that the smallpox virus emerged 3000-4000 years ago in East Africa and is closely related to the taterapox virus from African gerbils and to the camelpox virus, which causes variola in camelids. Today, smallpox virus strains are stored in freezers at the CDC in Atlanta and at the Vector Center in Koltsovo, Siberia. That is why smallpox remains a potential threat to the highly susceptible human species, as a result of an accident or malicious use of the virus as a biological weapon.

Los orígenes de la vacuna / The origins of the vaccine

La medicina china y su cultura ancestral parecen tener los antecedentes más remotos de los intentos por prevenir o curar el azote epidemiológico de esa época: la viruela. Estos conocimientos empíricos llegaron al Asia Central y Europa, y algunos granjeros hicieron observaciones de la utilidad de la inoculación o variolización sin llegar a documentar sus ensayos en la comunidad científica. El mérito de Edward Jenner reconocido como el descubridor de la vacuna antivariólica, radica en haber demostrado con evidencia práctica la protección conferida frente a la enfermedad por la administración en un niño sano de un material proveniente de una persona con lesiones causadas por el cowpox, virus de la viruela vacuna. Desde Europa en el siglo XVIII y comienzos del siglo XIX, la inoculación primero y luego la vacunación llegan a Hispanoamérica por vías informales o por determinación de la corona como un servicio a las colonias. La vacunación antivariólica tuvo el valor agregado de motivar y convencer a las autoridades gubernamentales sobre la necesidad de implementar políticas de salud pública para responder a las necesidades sanitarias de la población. En Chile, Fray Pedro Manuel Chaparro fue el pionero en la aplicación y difusión de la vacuna, realizó la primera campaña nacional y se cuenta entre los padres de la salud pública nacional.

Chinese medicine and its ancestral culture seem to have the most remote history of attempts to prevent or cure the epidemiological scourge of that era: smallpox. This empirical knowledge reached Central Asia and Europe, and some farmers made observations of the usefulness of inoculation or variolization without documenting their trials to the scientific community. The merit of Edward Jenner, recognized as the discoverer of the smallpox vaccine, lies in having demonstrated with practical evidence the protection conferred against the disease by the administration in a healthy child of a material from a person with cowpox lesions. From Europe in the eighteenth and early nineteenth centuries, first inoculation and then vaccination arrive in Latin America by informal means or by determination of the crown as a service to the colonies. Smallpox vaccination had the added value of motivating and convincing government authorities about the need to implement public health policies to respond to the health needs of the population. In Chile, Fray Pedro Manuel Chaparro was the pioneer in the application and diffusion of the vaccine, conducted the first national campaign and is counted among the parents of national public health.

Historical context and the roots of Jenner's discovery.

May 2016 marks the 220th anniversary of Edward Jenner's first experimental vaccination using cowpox to protect against smallpox. Jenner's discovery, and its rapid adoption around the world, launched a medical revolution that continues to shape how we approach disease prevention. The historical roots of vaccination are found in the popularization of smallpox inoculation during the 18th century, part of an Enlightenment culture that fostered scientific inquiry and the global circulation of knowledge. Jenner was part of that culture and his study of cowpox stemmed from his varied interests as a natural historian, his contacts with leading savants in London, and his medical practice in a flourishing dairy area of England. The amazingly quick spread of vaccination resulted from organized hospital trials in major cities, the severe smallpox epidemic at the turn of the century, disease environment, and policies of European colonial powers.

An examination of John Fewster's role in the discovery of smallpox vaccination.

Edward Jenner is recognised today as the father of vaccination but, as this paper explores, he was not the only Gloucestershire doctor to be linked to this discovery. John Fewster, a local surgeon and apothecary, is also said to have experimented with vaccination, many years before Jenner. This claim is made in a letter addressed to John Coakley Lettsom, written by John Player, a Quaker farmer. Player describes in detail Fewster's realisation that cowpox could be used to protect against smallpox. This letter is frequently cited but has not previously been subjected to critical analysis. We have identified several inconsistencies, including conflicting dates and a possible ulterior motive in that Player's son was to marry Fewster's daughter. We think it unlikely that Player, a devout Quaker, would have consciously fabricated evidence, but argue that the discrepancies in his account undermine the assumption that Fewster carried out vaccination experiments prior to Jenner. We also explore the assertion that Fewster presented a paper in 1765 on the subject of cowpox and its protective effect over smallpox. We conclude that, although there is no doubt that Fewster did pre-empt Jenner's discovery of vaccination, he did not realise the significance or importance of this momentous medical advance.

In celebration of the 200th anniversary of Edward Jenner's Inquiry into the causes and effects of the variolae vaccinae.

This review commemorates the 200th anniversary of Edward Jenner's development of a vaccine for variola, the cause of smallpox, and the 20th anniversary of its eradication. Jenner's original 23 case reports are briefly revisited within the context of earlier attempts to prevent this dreaded disease and in light of the current understanding of vaccinology and immunology. In addition, with molecular biological information available about many pox viruses and detailed sequence knowledge of some, it is now possible to appreciate Jenner's prescient accomplishments more fully.