The concept of disease and how to attack diseases has varied through the centuries and in each culture. But, some have existed and others have originated that, regardless of the cultural environment in which they have sprouted, have killed millions of human beings. Many lives have been saved with the discovery of sulfonamides and penicillin and its derivatives, however, more lives have been saved from the preventive action of vaccines.

Until the 19th century, the calamity of humankind was smallpox. Neither plague nor malaria together had claimed as many lives as smallpox. The plague was brought under control by the control of rats and fleas; malaria by the discovery of quinine and insecticides. As for smallpox, that disease that if it did not kill, it disfigured, its cure was based on a "fluke", which would lay the foundations for the prevention of many other diseases.

Cowpox

At the end of the 16th century in the English province of England, a young man named Edward Jenner realized that cow milkers did not suffer from smallpox because when they were infected with the -unknown to humans- cowpox, they were "protected" against human smallpox. Years later, in 1796, he would discover and prove in a child, that by inoculating material from the rashes that the cow milkers had on their hands, in other people, the latter were also protected. It was this inoculation of cowpox that was later called a vaccine. Inoculation against smallpox was spread throughout Europe using the arm-to-arm technique, i.e., from the rashes produced on the skin by cowpox.

The vaccine in Mexico

At the beginning of the 19th century, as a consequence of the serious smallpox epidemics in the "New World", the Philanthropic Expedition was organized in Spain, in which twenty-two children transported the vaccine from arm to arm to America. However, the technique also arrived by other means, in addition to arm to arm. This form of defense spread throughout the West Indies until it reached Mexico.

In Mexico, the method spread from places that operated as incipient vaccination "centers". In 1868, Ángel Gaviño Iglesias brought from France an isolate of the virus that caused smallpox, which finally led to its massive use. In 1912, the first laboratory that produced vaccines on a large scale was founded in Yucatan. By 1926, by presidential decree, vaccination against smallpox was made mandatory. Apparently, in 1951, the last case of the disease was reported in San Luis Potosi.

In May 1980, during the Thirteenth World Health Assembly, smallpox was declared eradicated from the planet. Only samples of the virus remain, for scientific purposes, in research laboratories in the Russian Federation and in the United States of America, with the instruction that they will be completely destroyed.

Unfortunately, not all diseases have this happy ending. Vaccines are the safe and effective way in which the organism defends itself, but only against certain diseases, since against others, due to the complexity of the microorganism that produces them, some type of immunizing agent has not yet been possible. The most current and dramatic example is AIDS.

Vaccine research has gone through several stages, all of them definitive in the
in the evolution of the fight against diseases. The first was the use of attenuated or killed forms as immunizing agents. That is, the moment a healthy person receives these agents, which do not have the ability to make him sick, he forms antibodies that will serve him in case an infectious agent enters his body.

Another stage was the use of natural or recombinant components of complete microorganisms. And, a final stage, which is still in the research phase, is the so-called "DNA vaccines", which consist of the inoculation of a gene - for example of an infectious virus - directly into an individual (it has been tested in mice) to induce immunity. Once the research and quality control tests have been completed, specialists foresee great promise for this technique.

Vaccines in Mexico

In each country, there are vaccination programs, especially for children, according to the type of diseases suffered by the population of each country. However, diseases or infectious agents are increasingly crossing borders due to the lifestyle of today's populations. An example of a disease that seemed more or less under control a few decades ago is tuberculosis, however, currently, the World Health Organization declares that tuberculosis, more than ever in the history of mankind, is a serious public health problem worldwide. The National Vaccination Program in Mexico indicates that the following vaccines are mandatory.

Anti-poliomyelitis, which protects against poliomyelitis or infantile paralysis. Polio is an infectious disease caused by a virus that enters the body through the mouth or nose and mainly affects the legs, causing flaccid paralysis, disability, and, in some cases, death. The global campaign against poliomyelitis is one of the strongest and the disease is clearly on the way to eradication. The last recorded case was in Peru in 1991.

The poliomyelitis virus enters the body by ingestion of food, water, or utensils contaminated with feces or saliva of sick people or carriers of the virus. Incubation lasts from 3 to 35 days. It initially settles in the throat for 3 to 7 days. Symptoms are fever, headache, nausea, and stiff neck and back. The only way to prevent it is through live attenuated virus vaccination (DPT), which protects against three diseases: diphtheria, pertussis, and tetanus.

Diphtheria is an infectious disease caused by a bacterium known as Corynebacterium diphteriae that attacks the tonsils, throat, nose, and skin. The bacterium enters the body via the nose, mouth, or a wound in the skin. It mainly affects unvaccinated children under five years of age. It is acquired through secretions produced by a sick person. Symptoms are fever, sore throat, hoarseness, chills, and sometimes paralysis of the neck muscles.

Whooping cough is a disease that affects the respiratory tract, caused by a bacterium called Bordetella pertissis. It enters the body through the nose and mouth and is characterized by coughing spells with a high-pitched whooping sound. It mainly affects children under five years of age and the younger they are, the more serious it is. The incubation period usually lasts from seven to ten days, but contagion may occur from the onset of symptoms until the third week after the onset of the disease. It starts with a cold and cough, followed by nocturnal coughing spells. The most serious complication is pneumonia.

Tetanus is a disease that affects the nervous system. It is caused by a bacterium known as Clostridium tetanus. It is acquired from contact with the organism, which lives in soil, street dust, rusty metal objects, and the excrement of some animals, mainly cows, and horses. The bacterium enters the body through all types of wounds. In newborns, the disease is caused by the use of unsterilized scissors, knives, or razors to cut the umbilical cord. The incubation period ranges from four days to three weeks and it is not transmitted from person to person.

Symptoms are headache, sweating, and stiff mouth; a grimace called "sardonic laughter" appears, painful muscle contractions that cause stiffness of the body, and the back arches from the waist to the shoulders. In severe cases, it can cause death by cardiac arrest. Tetanus affects people of any age and if an infection is survived, it can recur if the vaccination schedule is not kept up to date, because it does not produce sufficient immunological memory. The DPT vaccine contains attenuated organisms of tetanus and diphtheria bacteria, in addition to killed pertussis microorganisms.

Measles is a contagious disease caused by a virus that enters the body through the nose, mouth, and eyes. It is characterized by eye irritation, high fever, and a conspicuous red rash on the skin. Although it can affect people of any age, children under five years of age are most prone to it. It is easily transmitted through the cow secretions of sick people. The incubation period is about two weeks and the contagion starts four days before the spots appear. Symptoms are cold, sore throat and high fever, cough, watery eyes, and discomfort in the light.

Tuberculosis is a chronic, slowly progressive, contagious disease. It occurs at any age and mainly affects the lungs, although it can affect other tissues or organs of the body. It is caused by a bacterium called Mycobacterium tuberculosis or Koch's bacillus, in honor of its discoverer. It is transmitted through secretions expelled when coughing. It can be transmitted by drinking raw milk from a tuberculous cow.

The incubation period can last from two to twelve weeks, however, it may take years for the disease to present itself. There are two main factors that have led to the alarming proliferation of tuberculosis: the association between AIDS and tuberculosis and the emergence of antibiotic-resistant isolates of tuberculosis bacteria. The battle against other diseases, based on vaccines to prevent them, is underway. There have been encouraging advances against influenza, cholera, and malaria; however, the world's attention is focused on studies to achieve a vaccine against what has been called the disease of the century: AIDS.

The National Vaccination Program in Mexico states that the following vaccines are mandatory: Polio (Sabin), Diphtheria, Pertussis, DPT, Tetanus, Measles, Tuberculosis in its severe forms.

By Luci Cruz Wilson