The power of vaccines to eradicate diseases

Since the beginning of December, vaccines against covid-19 have been administered in several countries, including Spain. Throughout history, vaccination processes have managed to eradicate other pathologies such as smallpox and rinderpest. Others are in the process of being eliminated around the world.

High fever, fatigue, and severe back pain, and sometimes abdominal pain and vomiting. These were some of the symptoms of smallpox, an acute contagious disease, caused by the variola virus, which was also characterized by the eruption of pustules filled with fluid and then pus, spread first on the face and then on the body of the sick people who ended up covered in scabs.

Millions of people died from this pathology, which is believed to have existed for 3.000 years and was transmitted through close contact between people through infectious droplets. In the 300th century alone, there were between 500 and 30 million deaths due to smallpox, which is fatal in XNUMX% of cases.

For this reason, the World Health Organization (WHO) launched a definitive plan in 1967 to eradicate it through the vaccine that the British doctor Edward Jenner had achieved in 1796 and which he had been administering since then. In the mid-1977th century, vaccination became global and the last known natural case occurred in Somalia in XNUMX.

"At first there was a lot of reluctance to vaccinate, even Edward Jenner was ridiculed with caricatures. We are talking about the beginning of the 19th century. Bringing the vaccine to the colonies and the New World was a great challenge, but little by little it spread and it took a while more than a century to end up eradicating smallpox," says José Antonio López Guerrero, director of the Neurovirology group of the Molecular Biology department of the Autonomous University of Madrid.

It happened on December 9, 1979, when the WHO declared the end of this human infectious pathology, which was the first – and until now the only human one – that humans have managed to eradicate thanks to the immunization of the entire population. "Vaccination was suspended after eradication and now most people under 40 have not been vaccinated," explains David Heymann, an American epidemiologist at the London School of Hygiene and Tropical Medicine.

According to the researcher, the immunity from the vaccine persists four decades later, "but it is not known exactly how much longer. It is assumed that it has provided lifelong immunity to the majority of vaccinated people," Heymann specifies.

Effective global coordination

Although there have been other attempts to eradicate other diseases – that is, control and elimination worldwide without exception – only smallpox and rinderpest have been successfully eliminated through vaccination.

The latter became the first animal disease to be eradicated in human history. Its end was declared in 2011 by the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health (OIE) after 20 years of campaigning. world to end this viral pathology that attacked livestock.

"Although rinderpest did not infect humans, it did cause serious food shortages over the centuries," emphasizes the American epidemiologist. His final not only recognized the scientific community, which undertook global vaccination programs and strong virus control measures, but also international cooperation and coordination.

In the case of smallpox, the expert, who has worked for more than 22 years at the WHO, where he led the global response to SARS in 2003, points out that its eradication occurred thanks to "an effective vaccine, the fact that there was no a reservoir in nature, that all infections were expressed clinically in the same way and that the search and containment strategy was highly effective and easy to achieve.

Could the same happen with vaccines against covid-19 or other diseases? "Not all of them have proven to have a weapon in vaccination. There are viruses like HIV with which we have been in a pandemic since 1980 trying to develop vaccines. Not all pathogens are susceptible to having vaccines against them," clarifies the Spanish virologist.

The complication in finding a vaccine may lie in the route of entry of the virus or in the form of infection, such as the AIDS virus, which integrates into cells. "In many other cases it is because they are diseases that have not aroused economic interest in investing in their eradication," confesses the UAM researcher. According to him, for a disease to be susceptible to a vaccine, the pathology has to become global or affect the first world, "where research and pharmaceutical companies show a clear interest."

In the case of malaria, achieving a vaccine would help prevent two million additional cases and four million deaths by 2030, for example. "More and more money is being invested in this disease and different vaccines of limited effectiveness are being produced, but nothing comparable to what is happening with the coronavirus has been achieved. Global coordination and economic investment have been unprecedented in the history of humanity," emphasizes López Guerrero.