Generality
The flu vaccine is a preparation that defends the body from the influenza virus, stimulating it to develop antibodies against it. The vaccination is practiced annually, since the flu virus often changes and as the vaccine itself slowly loses its effectiveness. The preparation of the preparation is not mandatory, but is particularly indicated for certain categories of people, such as children, adolescents, the elderly and individuals suffering from particular diseases.
The flu vaccine is not 100% effective, but it is quite safe. There is a possibility, albeit low, that in predisposed individuals the preparation triggers an adverse reaction to one or more substances present in the vaccine. Not everyone, therefore, can undergo treatment; however, even when vaccination is impractical, flu can still be prevented in alternative ways.
What's this
The flu vaccine is a special preparation that protects against the influenza virus . Influenza is an infection of the respiratory tract, capable of causing very serious complications in some particular individuals, such as children and young people who attend kindergartens and schools, the elderly and subjects with a depression of the immune system ( immunosuppressed ) or with respiratory disorders (NB: depression of the immune system means an ineffective immune defense).
Although the protection provided by the preparation is not complete, the flu vaccination is one of the most effective resources against influenza.
HOW DOES A VACCINE WORK? THE ANTIBODIES
The flu vaccine, like all antiviral vaccines, stimulates an individual's immune system to produce specific antibodies against a virus, in this case of influenza.
Antibodies, or immunoglobulins, are globular proteins that can recognize foreign microorganisms ( antigens ), which can infect the entire human organism, and destroy them by specific cells of the immune system.
The antibodies are secreted by particular immune cells, called B lymphocytes, and act as surface antennas of the latter. In the presence of an antigen, the immunoglobulins exposed on the surface membrane of B lymphocytes are activated, signaling to the B lymphocyte itself to produce other specific antibodies against the detected antigen. From here on, the defensive barrier, erected by the human immune system, becomes increasingly powerful and effective. In fact, a large number of antibodies are produced, which, circulating through the blood, trace the antigens present in the body and recall the cells ( phagocytes and cytotoxic cells) responsible for the destruction of foreign microorganisms.
At the end of this process, singular B lymphocytes are formed, able to recognize the antigen already encountered (and eradicated) earlier, if it were to recur. These B lymphocytes are also known as " memory cells " and the mechanism by which they are created, called " immune memory ", is the basis of antiviral vaccines.
Since when is it available?
The flu vaccine is produced by some pharmaceutical companies, which put it on the market after its completion.
Generally, the first availability starts from August / September, or slightly earlier than the ideal period for vaccinating, which is between October and November, and well in advance of the flu season, which corresponds to winter .
It is good practice to undergo vaccination in the period recommended by doctors, as the vaccine takes two weeks to "build" the immune memory against the influenza virus.
Getting late and in the middle of the flu season may be useless, because you run the risk of getting sick when the memory cells are not yet ready.
Why get vaccinated every year
There are two reasons why one needs to be vaccinated annually against the flu:
- The main reason. The flu virus has the ability to change its appearance very quickly, within a few months. Consequently, after a year, the vaccine of the previous flu season is completely inadequate to face the new virus, created by the antigenic mutation of the one to which it was effective.
Indications and Contraindications
Who can and cannot be vaccinated?
Except for special exceptions, all individuals from 6 months of age up can be vaccinated against the flu.
In particular, the doctor strongly recommends the flu vaccine to the following categories of people:
- Pregnant women, because the flu virus could be transmitted to the fetus and complicate pregnancy.
- Children and adolescents, because they have "fragile" immune defenses and spend a lot of time in crowded environments (kindergartens, schools, etc.), where the virus is transmitted with speed and ease.
- Elderly, due to a physiological reduction of the immune system.
- All those who suffer from particular health problems or are pathologically immunosuppressed ; in these people, the flu virus could trigger serious complications. The following table shows the pathological conditions in which the vaccine is recommended.
Pathological states for which influenza vaccination is advocated.
- Asthma
- Tumor or people in the middle of an anticancer therapy
- Cardiovascular diseases (congenital and acquired cardiopathies)
- Chronic obstructive pulmonary disease
- Cystic fibrosis
- Diseases of the hematopoietic organs
- Diabetes
- AIDS (HIV)
- Kidney diseases
- Liver disease
- Obesity
WHO IS THE VACCINE CONTRAINDICATED FOR?
The flu vaccine, in some situations, is contraindicated. Therefore, before undergoing vaccination it is advisable to consult your doctor and request a consultation, to find out if you are fit or not.
The situations that make the achievement of the flu vaccine problematic are in fact two:
- Suffering from an egg allergy . Egg protein is an ingredient used to prepare all the most marketed influenza vaccines, regardless of which seasonal flu virus is. Some individuals are allergic or hypersensitive to these proteins, so that, in contact with them, they develop an allergic reaction.
Egg allergy does not necessarily prevent the attainment of vaccination, but requires certain precautions. For example, one must stay with the vaccine and for at least 30 minutes / hour in the hospital or medical center where the treatment was obtained. If at the end of this time interval, the vaccinated individual has not shown allergic or hypersensitivity reactions, it means that, most likely, the preparation has not affected the organism.
Some pharmaceutical companies have created special vaccines, free of egg proteins; these preparations have been approved by the FDA (US government agency for the regulation of food and pharmaceutical products), but can only be used by people over the age of 18.
- Having responded negatively, in the past, to another flu shot . Some individuals, after the flu vaccine, may be the protagonists of a serious adverse reaction. In such situations, it is not recommended to undergo a second vaccine again, even years later, because the consequences could be more serious than those that occurred previously, during the first episode. In any case, it is good practice to request a medical consultation to trace the causes of the problem.
Vaccination Mode
How many vaccination modalities exist?
An influenza vaccine is "built", like all viral vaccines, using some fragments of the virus you want to fight. These fragments are the so-called antigens, which activate the immune system.
The flu vaccine is available in two different versions.
An injectable version consists of inactivated (or killed) fractions of viruses. The other version, which can be administered through a nasal spray, contains attenuated (or weakened) fractions of viruses.
INACTIFIED INACTIVATED VACCINE
The inactivated influenza vaccine, administered by injection, is composed, as mentioned, of parts of killed virus, completely harmless to the organism but capable, however, of inducing the development of an effective antibody response (ie the production of antibodies) .
The preparation can be administered, on a person's arm, by an intramuscular injection or an intradermal injection . Intramuscular injection, from 6 months of life onwards, is available to everyone, while intradermal injection is reserved for people aged 18 to 64 years.
The different types of inactivated influenza vaccines:
- Split vaccine
- Virosomal vaccine
- Adjuvant vaccine
- Intradermal vaccine
CURED VACCINE TAKEN BY NASAL SPRAY
The attenuated influenza vaccine, which can be administered through a nasal spray, is prepared with tiny fragments of live virus, but weakened. Virus doses are so small that they are unable to cause influenza, but only a specific antibody response (which is the target of the preparation).
The attenuated vaccine is forbidden in the event of pregnancy and can only be taken by healthy people who have a minimum age of 2 years and a maximum age of 49.
The possibility of using the attenuated flu vaccine, in the form of a nasal spray, is recent: it is only since 2011, in fact, that the European Medicines Agency has approved its use in Europe (and in Italy).
Table. The main differences between the inactivated and the attenuated influenza vaccine.
| Inactivated vaccine | Attenuated vaccine |
It is given by injection, therefore it requires the use of a needle. | It is administered via a comfortable nasal spray. |
Contains fragments of killed virus, therefore harmless. | It contains small fragments of live viruses that fail to cause influenza, but on rare occasions could transmit the viral infection to those living with the vaccinated individual. |
The intramuscular version can be administered from six months of life onwards. | It is prohibited in case of pregnancy and can only be taken by people between 2 and 49 years old. |
It can be taken by pregnant women and by all people who are immunosuppressed and not in perfect health. | It cannot be given to individuals with a depression of the immune system (immunosuppressed) and who are suffering from asthma, AIDS, cystic fibrosis, etc. |
Side effects
Can the vaccine cause flu and / or complications?
While containing within it small fragments of viruses, the flu vaccine is a safe treatment, which does not cause influenza (provided, of course, that the methods of use are respected).
- An overreaction to the vaccine . Some individuals respond to vaccination with a strong immune reaction. If the vaccine is injectable, this reaction consists of muscle pain and fever, both lasting a few days; if, instead, the vaccine is in the form of a nasal spray, the possible disorders consist of a runny nose, headache and sore throat.
- Get the flu for two weeks after vaccination . This eventuality is rare, but it can take place, especially if the flu season vaccine is started. With the influenza virus in circulation, in fact, the chances of getting sick increase accordingly and, until the two weeks necessary for the creation of the immune memory have passed, the vaccinated individual is exposed to the virus like the unvaccinated subjects. It is clear that, in these cases, it is not a side effect of the vaccine, but a lack of precaution and timeliness on the part of those who use the treatment.
- Preparation error . It has happened in the past that the vaccine produced was not suitable for the flu virus of the current season. This meant that the vaccinated people were less protected and, in some cases, became ill with the flu. A vaccine made properly and without errors of this kind, allows effective protection.
- Other viral infections, with flu-like symptoms . Several infectious viruses, such as the cold virus ( rhinovirus ), trigger respiratory problems that are mistakenly mistaken for flu. The flu vaccine cannot protect against such infections and is a completely normal thing, given that it is created for other purposes.
Is it always effective?
Earlier, there was talk of influenza vaccine as a safe vaccine, as its administration does not cause influenza.
However, this does not exclude the possibility that vaccination may fail: in this case, by failure, we mean the failure to create an effective immune memory.
Thanks to the statistical data of past years, it was possible to calculate the success rate of the vaccination against influenza, which turned out to be around 60-70%. Furthermore, from a more accurate analysis of these same data it emerged that, in the years in which the vaccine was used more, the success rate was higher. This best response to the vaccine is explained by the following concept: the more people are vaccinated against the flu virus, the more difficult it is for this virus to spread and circulate in the population. This mechanism, valid for all viruses and their vaccines, is known as herd immunity .
alterantive
Without the vaccine, can the flu be prevented?
Individuals who are unfit to receive the flu vaccine and at the same time are also immunosuppressed, can try to prevent the flu with alternative methods.
These methods, which are valid, in reality, on every occasion, are based on correct daily hygiene and consist of:
- Wash your hands often with soap and water.
- If you don't have soap, use alcohol-based healthcare solutions to wash your hands.
- Avoid touching, with your hands (especially if they are not clean), the eyes and the internal parts of the nose and mouth.
- Avoid going to crowded places in the middle of the flu season. This advice is particularly indicated for immunosuppressed and those in whom a flu can trigger serious complications.
Why doesn't a healthy adult require vaccination?
To answer, readers must be reminded that the flu virus is a virus that can change its external characteristics very quickly.
These changes sometimes give the new virus the appearance of a previous flu virus, which appeared perhaps many years ago; in other words, they create, in a completely random way, a double of an old flu virus presented in another age. This "new-old" virus, for the adult and healthy people who have already met it in the past (and if they have fallen ill), is not particularly dangerous, due to the question (described above) of the immune memory; immune memory which, formed in the aforementioned way, is much stronger and lasting than that which develops after an influenza vaccine.
