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Why do you have to get a flu shot every year?


Influenza is an acute infectious disease of the respiratory tract caused by influenza A or B viruses. Every year, millions of people become ill with influenza. It usually causes a mild illness, but can be serious and even fatal for people considered at risk: people over 65 years of age, newborns and people with chronic pathologies.

In fact, the percentage of people at risk of influenza infection in the European Union is estimated at 49.1% of the total population. For this reason, annual influenza vaccination is essential for certain individuals.

Vacuna de la gripe

Who should be vaccinated?

Annual influenza vaccination is recommended for persons over 65 years of age, pregnant women and persons in direct contact with risk groups. In addition, it is vitally important to vaccinate children (older than 6 months) and adults with chronic diseases such as asthma, diabetes, kidney disease, immune system diseases or obesity, among others. These diseases sometimes take time to appear.

Thanks to a genetic test it is possible to know the predisposition to suffer from some diseases arising as a consequence of complications in the vaccine. For these people it is also highly recommended to be vaccinated annually.

Genetic movement of the virus

One of the characteristics of influenza is its high capacity of contagion from one person to another. Influenza appears, above all, in winter and in an epidemic way, that is to say, every year there is a season in which there can be a great activity and circulation of the influenza virus. It is a major health problem, as it can lead to complications and sometimes even death. The influenza virus has an annual incidence of 5-10% in adults and 20-30% in children.

Influenza virus A or B has high genetic variability. Variation may result from genetic drift, i.e. the accumulation of point mutations in the genes encoding the virus surface proteins (surface antigens). These variations imply the emergence of new influenza viruses each season. As a result, the influenza vaccine is modified annually to adapt it to the strains thought to be circulating each season.

Another variation that the influenza virus can undergo is as a result of genetic exchange between animal and human viruses, whereby these new viruses can be transmitted from one person to another. In this case, the new virus can give rise to a pandemic, characterized by affecting people all over the world, such as COVID-19, influenza A, Spanish flu or Asian flu.

It is therefore essential to promote vaccination campaigns, since the variability of this virus means that a person can become ill with influenza again at another stage of his or her life as a result of the loss of effectiveness of the antibodies previously generated.

Does the vaccine contain the virus?

But what are vaccines really? Vaccines are preparations consisting of an agent similar to the microorganism causing the disease. When this attenuated part (but incapable of producing the disease) is introduced into an individual’s organism, the latter recognizes it as something foreign and creates antibodies against it. Thanks to immunological memory, when the individual comes into contact with the virus, his or her immune response will be much faster and more effective.

However, the administration of vaccines can lead to certain undesirable effects. An adverse reaction to vaccines is a harmful and unintended reaction that can be mild, moderate or severe. Vaccines are administered to healthy people for preventive purposes, therefore, a maximum safety profile is paramount. It is also important to know the precautions and contraindications of each vaccine to avoid putting the individual’s health at risk.

Adverse reactions are classified according to WHO into vaccine-induced reactions, reactions due to defects in vaccine quality (a consequence of the intrinsic characteristics of the vaccine), reactions due to program errors (storage, transport, handling or administration) and reactions due to anxiety about the act of vaccination.

Adverse effects of influenza vaccination are usually mild and, in fact, may resolve without medical support. Some of the most common reactions at the injection site are pain, redness and swelling; whereas, systemic reactions such as fever, nausea, myalgia and headache may also occur. Interestingly, the scientific literature shows that adverse effects are more frequent in young people than in the elderly, and especially more frequent in women than in men. However, young women, the white population and the elderly are the groups most likely to receive the vaccine.

Consequently, it is interesting to know the genetic factors associated with the adverse effects of the vaccine, since this would make it possible to foresee the harmful effects before vaccination and thus try to reduce, as far as possible, their harmfulness. In this sense, this genetic information can be obtained by means of the tellmeGen DNA test.