Basic facts about vaccination and vaccines

Vaccination is one of the top ten public health achievements in medical sciences that has helped to reduce illnesses and the mortality rate as well as to increase life expectancy. Many infectious diseases, which in previous centuries caused major epidemics, a high death rate and sometimes decimated the population of certain areas, are almost nonexistent or even completely eradicated thanks to the introduction of vaccination. Every year vaccination saves over three million lives and protects even more millions of people from the permanent effects of diseases. However, all over the world infectious diseases which could be prevented with vaccination still cause the death of 1.4 million children under the age of five.

In Slovenia, systematic vaccination has eradicated , poliomyelitis and diphtheria. Measles, mumps and rubella occur very rarely, as do tetanus and infections with the Haemophilus influenzae bacteria. Whooping cough is also relatively rare. An improved standard of living, sanitary-hygienic measures and healthier diets are not the only reasons for the sharp decrease of infectious diseases against which people are being systematically vaccinated. This is confirmed by the fact that the majority of the population, regardless of improved living conditions, still recover from some infectious diseases that are not treated by systematic vaccination (for example chickenpox). At the same time, the introduction of some vaccinations only in this century, when sanitary-hygienic conditions have not seen much improvement, enabled the almost complete elimination of certain diseases (for example vaccination against Haemophilus influenzae).

The history of vaccination started in China with vaccination against smallpox more than 2000 years ago. Modern vaccination against smallpox started in 1796 and with worldwide systematic vaccination the disease was eradicated by late 1970s. The main purpose of vaccination is to prevent the outbreak of the disease and its possible complications and consequences. Vaccination is used particularly against diseases for which there is no successful treatment available. It enables individual immunity and by vaccinating a large share of the population in a certain area, community immunity can be achieved, which prevents microorganisms from spreading among people and ensures the protection of those who have not yet been vaccinated, those who did not develop immunity after the vaccination or those who cannot be vaccinated due to common diseases. This is especially true for diseases that are transmitted by people. Community immunity is also proven by the recurrence of contagious diseases in areas where the percentage of vaccinated people decreases below a certain level. The most important protection against diseases transmitted to people by animals or through contact with an infected environment is individual protection through vaccination. One example is the vaccination against tick-borne encephalitis. In Austria, over 90% of the population is vaccinated against this disease and the number of those affected is 10% lower than before the introduction of the vaccination. In Slovenia, the number suffering from this disease is not decreasing because only around 15% of the population is vaccinated against it. Although due to common vaccination practices in Slovenia, some diseases are rare or even no longer occur, continuing systematic vaccination remains an important measure for preventing these diseases from recurring and spreading.

Vaccination activates the human immune system, which produces specific antibodies that protect the organism from the cause of the infectious disease when it enters the body naturally. Upon first contact with a particular microorganism, the human body needs some weeks to contain the disease. During this period, permanent organism damage may occur. A vaccinated person is already prepared for this kind of infection and can respond to the invasion of a particular microorganism and disable it more quickly. Vaccination is carried out with dead microorganisms, parts of microorganisms or weakened live microorganisms, which cause no harm to the majority of vaccinated people.

All the modern vaccines used in vaccination programmes are proven to be safe and effective. Even before the permission for their use is obtained, tests are carried out for several years to determine their effects, side effects and impact on different groups of people. First, tests are carried out on small groups of people to confirm the safety and effects of new vaccines. Later on, in the final research phases, their effects and safety are tested on tens of thousands of people by comparing vaccinated and non-vaccinated groups. Only after obtaining solid evidence on the safety and effects of a certain vaccine do regulatory organisations give permission for its broader use. In Europe, the safety and effects of vaccines are in the hands of the European Medicines Agency. Quality control of all imported series of vaccines in Slovenia is additionally carried out by the Public Agency of the Republic of Slovenia for Medicinal Products and Medical Devices. Along with the wide use of vaccines, post-marketing supervision of vaccine safety is also carried out by keeping records of side effects, which are then reported to supervising institutions by those carrying out the vaccination. This helps to identify additional very rare side effects that might not yet have been discovered due to the limited number of people involved in previous phases of research. The use of some vaccines was halted soon after the permission for broader use was issued because they caused very rare side effects (for example intussusceptions caused by the first generation vaccines against the rotavirus infection, which have not been used since).

The use of vaccines, like any other medicine, might have side effects. Accurate identification and taking into account of the indications and contraindications (when the vaccination can or cannot be performed) can reduce the risk of side effects. Health problems occurring soon after vaccination might be side effects related to the vaccination itself or to incorrect vaccination technique, or they might be coincidental and would occur even if the person had not been vaccinated. Relatively frequent side effects are those that occur after the vaccination at the place of injection; these are usually mild, temporary and have no long-term consequences. Systemic reactions (for example fever or rash) are rare and usually not dangerous. Incorrect measures may lead to dangerous allergic or anaphylactic reactions, which occur very rarely (one in a million vaccinations). Numerous studies have rejected various hypotheses on a connection between vaccination and autoimmune diseases, autism, multiple sclerosis, diabetes, rheumatoid diseases, sudden infant death, asthma and other diseases. Very few studies have shown a possible connection between vaccination and specific health problems and these have been criticised as methodologically incorrect (the vaccination against measles, mumps and rubella was supposedly connected to the development of autism in children). Opponents of vaccination connect even particular ingredients of vaccines to specific health problems. Due to public pressure, since 2000 vaccine producers have removed from all vaccines thiomersal (organic mercury), which was used in vaccines as a preservative. The number of diseases that were supposedly related to this supplement did not diminish after the removal of this ingredient. Further research rejected the presupposed connection between thiomersal and certain diseases that occur in childhood and adolescence. Opponents of vaccination claim that other vaccine supplements used to ensure vaccine stability and the desired response after the vaccination are similarly “dangerous”. The majority of vaccines contain very low levels of aluminium salts, which enter our bodies in much larger amounts through food and certain medicines. Even breast milk provides babies with several times more aluminium than three doses of vaccine in their first year. And if babies are fed with infant formula, the consumption of aluminium is even higher.

The risk of severe side effects from vaccination is much lower than the risks posed by the development of the disease and possible complications for a non-vaccinated person. Measles, which has a recovery rate of 99% among the unvaccinated population, affected practically all Slovenes born before 1960, when vaccination was not yet introduced. Measles cause otitis media in 5% of the infected population, pneumonia in 1%, and in one out of a thousand children complications occur in the form of inflammation of the brain, which might have permanent consequences. Approximately the same percentage of those who are infected die. In contrast, inflammation of the brain after the vaccination occurs in fewer than one in a million vaccinated children. Due to refusal of the vaccination, the number of those suffering from this disease is still too high even in developed countries. In Europe, this disease affects 30,000 people and causes tens of deaths every year, but it remains a European goal that after 2015 no more children will suffer from measles. Tetanusdiphtheria and whooping cough might also have fatal consequences but the vaccines against these diseases are almost completely safe.

Even vaccinated individuals might get the diseases against which they have been vaccinated. Some vaccines ensure long-lasting or even permanent protection while others require revaccination at set intervals. Not every vaccinated person develops protection after the vaccination and not every vaccine is 100% effective. The majority of vaccines that are used in routine vaccination of children are 85–95% effective. We can therefore assume that 5–15% of vaccinated people who are in contact with the cause of the disease will catch the disease anyway. This is why a high vaccination rate of the population is especially important as it reduces the risk for the entry and spread of the causes of diseases. Vaccines that contain weakened live microorganisms are generally more effective and protect 98% of vaccinated people.

The child vaccination rate in Slovenia is very high. More than 95% of children are vaccinated against all diseases included in the systematic vaccination of pre-school children. This ensures community immunity and prevents the entry and spread of these diseases in Slovenia. A small percentage of children cannot be vaccinated against some diseases due to particular health conditions. In Slovenia, vaccination against the majority of infectious childhood diseases is mandatory. The same system is applied in some other Central and Eastern European countries, while some Western European countries demand mandatory vaccination only against particular diseases. It is interesting that the percentage of vaccinated children is similar even in those European countries where the vaccination is not mandatory. Most parents are aware of the advantages that vaccination brings in comparison to the risks the child faces if he or she is not vaccinated. Even though the opponents of vaccination have a strong media presence, the percentage of parents who refuse to vaccinate their children due to their personal beliefs is relatively low.

 

Author: Zoran Simonović, MD, specialist in public health.

 

Translated by: Valentina Rebec.

 

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