Flu vaccine: who should take it and 7 other common questions

The flu vaccine protects against the different types of the influenza virus responsible for the development of influenza. However, as this virus undergoes many mutations over time, it becomes increasingly resistant and, therefore, the vaccine needs to be redone every year to protect vaccinated people against the new forms of the virus.

Generally, the vaccine is given through an injection into the arm and helps the body develop immunity against the flu, preventing the onset of flu-related complications such as pneumonia and other respiratory problems, in addition to hospitalization and death. For this, the vaccine exposes the person to a small dose of the inactivated flu virus, which is already enough to “train” the defense system to defend itself in case it ever comes into contact with a live virus.

The vaccine is available free of charge by the Unified Health System (SUS) for people who belong to the risk group, but it can also be found in private vaccination clinics.

1. Who should get the vaccine?

Ideally, the flu vaccine should be administered to people who are most likely to come into contact with the flu virus and develop symptoms and/or complications. Thus, the vaccine is recommended by the Ministry of Health in the following cases:

  • Children between 6 months and 6 years of age (5 years and 11 months);
  • Adults between 55 and 59 years old;
  • Elderly over 60 years;
  • Pregnant women;
  • Postpartum women of up to 45 days;
  • Health professionals;
  • Teachers;
  • Indigenous population;
  • People with compromised immune systems, such as HIV or cancer;
  • People with chronic illness, such as diabetes, bronchitis or asthma;
  • Trisomy patients, such as Down syndrome;
  • Adolescents living in socio-educational institutions.

In addition, prisoners and other persons deprived of their liberty should also be vaccinated, especially due to the conditions in their location, which facilitates the transmission of diseases.

2. Does the vaccine protect against H1N1 or coronavirus?

The flu vaccine protects against different groups of the flu virus, including H1N1. In the case of vaccines administered free by SUS, they protect against 3 types of the virus: influenza A (H1N1), A (H3N2) and Influenza type B, being known as trivalent. The vaccine that can be purchased and administered in private clinics is usually tetravalent, also protecting against another type of the Influenza B virus .

In any case, the vaccine does not protect against any type of coronavirus, including the cause of the COVID-19 infection.

3. Where can it be administered?

The flu vaccine offered by SUS to groups at risk is usually administered in health centers, during vaccination campaigns. However, this vaccine can also be made by those who are not part of the risk group, in private clinics, after payment of the vaccine.

4. Do I need to take it every year?

The flu vaccine has a duration that can vary between 6 to 12 months and, therefore, it must be administered every year, especially during the autumn. In addition, as influenza viruses undergo rapid mutations, the new vaccine serves to ensure that the body is protected against the new types that have emerged over the year.

Once administered, the flu vaccine starts to take effect in 2 to 4 weeks and, therefore, is not able to prevent the flu that is already developing.

5. Can I get the flu shot?

Ideally, the vaccine should be given up to 4 weeks before any flu symptoms appear. However, if the person already has the flu, it is advisable to wait for the symptoms to disappear before having the vaccination, to avoid that the natural flu symptoms are confused with a reaction to the vaccine, for example.

Vaccination will protect the body against another possible infection with the flu virus.

6. What are the possible adverse reactions?

Some side effects that may arise after applying the vaccine include the development of cold symptoms, such as chills or runny nose. In addition, a reaction may also develop at the bite site such as pain, swelling and redness. In this case, it is recommended to apply an ice pebble on the spot for a few minutes throughout the day, in order to reduce the swelling.

In more rare cases, headache, tiredness, muscle pain, weakness or unusual sensation in the arms and legs, high fever and abnormal bleeding may still occur.

7. Who should not get the vaccine?

This vaccine is contraindicated for people with bleeding, Guillain-barré syndrome, blood clotting problems such as hemophilia or bruises that easily appear, neurological disorder or brain disease.

In addition, it should also not be applied to people with allergies to eggs or latex, a weakened immune system, as in the case of cancer treatments or if you are taking anticoagulant drugs, as well as during pregnancy and lactation. 

8. Can pregnant women get the flu vaccine?

During pregnancy, the woman’s body is more vulnerable to infections and, therefore, there are great chances of getting the flu. Thus, the pregnant woman is part of the risk groups for influenza and, therefore, should have the vaccination free of charge at SUS health posts.

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