The anxiety for finding and efficient vaccine against SARS-CoV-2 highlights the importance of vaccination, although our notion of vaccines is, sometimes, rather simplistic as the ability to generate an immunity response which is protective and persistent enough depends on many factors. Therefore, perhaps, it is worth starting at the beginning and remembering how Humankind has gradually developed this preventive action which is so sought after in precisely the present situation.
It should be noted that one of the first great epidemics to affect Humankind (after the famous plagues of Egypt, if we believe what the book of Exodus tells us and for which National Geographic found a plausible explanation) was the smallpox virus which scourged East Asia in the 8th century, which we know about thanks to the system for noting disease used by the Tang dynasty. Probably, their interpretation that people who had suffered the disease did not get infected again stimulated the practice of what is called «variolation», an ancient practice which is well-documented as from the 14th century, at least in China. The method could be applied in different ways, for example dressing children in the clothes of sick people, or even inoculating —sometimes with the aid of a needle impregnated in pus from smallpox wounds— the virus in a healthy person, the best way to transmit the disease, certainly, but some «victims» of such temerity remained unscathed. This protective effect was analysed by Daniel Bernouilli, who worked out that the life expectancy of inoculated people was greater than that of those who were not, a calculation which brought him the prize from the French Academy of Sciences in 1760, as well as recognition for the first objectifiable evaluation of the possible effectiveness of a health intervention.
Variolation arrived in Europe in the hands of two Italian doctors, Giacomo Pylarini and Emmanuel Timoni, who both knew of the practice from having worked in Constantinople. Timoni also acted as interpreter for ambos Lady Mary Montagu, wife of the British ambassador to the Ottoman Empire, who, for personal reasons, became a fervent promoter of the practice. In Spain, the most notable promoter was a doctor in the Spanish Army, Timothy O’Scanlon, Irish by birth. The polemic between defendants and detractor of inoculation in the West were fierce and even virulent. In Massachusetts, USA, For example, Cotton Mather (the puritan pastor who became sadly famous for the Salem witch trials) led the stout defence of the practice, while Dr William Douglas (quoted by Adam Smith in his The Wealth of Nations as being a frank and honest man) condemned it incessantly. Sir Hans Sloane, then president of the Royal College of Physicians and vice-president of the Royal Society, in Britain, sided with Douglas. The debate deepened with empirical research by James Jurin, secretary of the Royal Society, and Zabdiel Boylston, a convinced Boston inoculator, presented at a monthly meeting in July 1726 at the Royal Society, presided by Isaac Newton. According to the data provided, fatality from naturally infected smallpox was between seven and eight times greater than fatality from inoculation, although this information did not temper the debate, until a few years later, Edward Jenner, a rural doctor with no academic pedigree but well-up on the controversy discovered the protective role of vaccination —in this case with lymph— from cow-pox when he observed that people who had milked sick cows did not develop human pox. Fortunately, cow-pox is much less virulent in humans, though not altogether harmless, so the balance between fatality from smallpox and that attributable to cowpox was much more favourable than with vaccination.
Nevertheless, the doubts, reticence and even opposition to vaccination against smallpox did not disappear completely, probably —at least in part— as a result of the government’s decision to make it compulsory, but maybe also because the conditions under which vaccination took place, until the general use of lancets and procedures for keeping the vaccine safe and active, it facilitated catching other infections.
The history of vaccinations is riddled with many other controversial episodes, such as the unfortunate «Cutter incident», in which, due to a deficiency in the deactivation process of poliomyelitis virus, around 200,000 children got a vaccine which is thought to have caused 200 cases of paralytic polio and 10 deaths, an event which happened during the first mass wave of vaccinations with the vaccine which Salk had found only three years earlier, in 1952, and which was one of the most successful epidemiological studies ever carried out —not even afterwards—. This episode would serve to establish strict manufacturing regulations, but did not interrupt vaccination programmes, probably because people valued the prevention of a disease which had, a few years before, caused thousands of cases of paralytic polio.
Andreu Segura, epidemiologist, retired Full Professor of Public Health at Barcelona University, is a founding member of the Sociedad Española de Epidemiología (Spanish Epidemiological Society) and the Sociedad Española de Salud Pública y Administración Sanitaria (SESPAS, Spanish Society for Public Health and Administration). From 1978 to 2016, he worked in the Health Department of the Catalonian Autonomous Government, during which time he was in charge of the medical statistics, epidemiological bulletin, AIDS prevention programme, Public Health Institute, Inter-departmental Public Health Plan, and the COMSalud Project, while contributing in the teaching of Spanish Public Health institutes. He is currently the coordinator of the SESPAS work teams on ethics and iatrogenesis, guest editor of Gaceta Sanitaria and member of the advisory board on Public Health and the Bioethics Committee in Catalonia.
As regards Timothy O’Scanlon, it is available on-line the paper by Pilar León Sanz and Dolores Barettino Coloma entitle «La polémica sobre la inoculación de las viruelas» in Vicente Ferrer Gorráiz Beaumont y Montesa (1718-1792): un polemista navarro de la Ilustración (Gobierno de Navarra, 2007), whence the illustration for this piece was taken.