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Flu shots - Types and Indications

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A flu shot is a vaccine made from the dead form of viruses that protects against severe cases of flu.

Medically reviewed by

Dr. Kaushal Bhavsar

Published At May 29, 2023
Reviewed AtJanuary 31, 2024


Flu is a respiratory illness caused by the influenza virus that infects the throat, lungs, and nose. Getting flu shots protects against severe cases of the flu. Even though most people who have the flu get better on their own, sometimes the complications can be severe. The best way to decrease the complications from the flu is by getting vaccinated every year.

What Are Flu Shots?

Flu shots are vaccines that give protection against the influenza viruses, which are responsible for causing flu, a respiratory illness that spreads quickly. Flu shots are primarily given in the arm using a needle. However, nasal spray flu vaccines are also available. The various ingredients in the flu shot ensure the vaccine is effective and safe.

What Are the Types of Flu Shots, and Who Can Take Them?

The different types of flu shots are as follows:

Quadrivalent Flu Vaccines:

These vaccines protect against four strains of the flu virus (two strains of influenza A viruses and two strains of influenza B viruses). The types of flu shots under this category of vaccines are as follows:

  • Regular Standard-Dose Quadrivalent Shot:

People above six months of age can take the regular standard-dose flu shot. A variant of the quadrivalent shot containing a virus grown in cell culture can be taken only by people who are four years old or older.

  • Jet Injection Quadrivalent Shot:

AFLURIA quadrivalent is a flu shot that gives protection against two influenza A (H1N1 and H3N2) viruses and two influenza B viruses. This flu shot can be administered by a needle in people above six months of age and by a jet injector in people under the age group of 18 to 64.

  • High-Dose Quadrivalent Shot:

The high-dose quadrivalent vaccine (Fluzone) has four times the amount of flu virus antigen (the vaccine component that stimulates the immune system and protects against the flu virus) as the standard-dose shot. This flu shot is specifically meant for people above 65 years of age, as they have a weak immune system and are more prone to flu-related complications.

  • Recombinant Quadrivalent Shot:

This flu shot is recommended for people over 18 years of age. As this vaccine is not manufactured from eggs, it can be used by people with severe egg allergies.

  • Live Attenuated Intranasal Spray:

This vaccine, administered as a nasal spray, contains severely weakened flu, unlike other vaccines that contain killed flu. It is contraindicated in pregnant women and is suitable for people between the ages of two and 49.

Trivalent Flu Vaccines:

This vaccine protects against three strains of the flu virus, namely influenza A (H1N1), influenza A (H3N2), and influenza B virus. The types of trivalent flu shots are as follows:

  • Regular Standard-Dose Trivalent Shots:

These flu shots can be taken by people between 18 and 64 and are administered using a needle in the arm muscle.

  • Trivalent and Quadrivalent Shots With Adjuvant:

These shots contain an additional ingredient, adjuvant, for creating a more robust immune system response. These are indicated for people above the age of 65.

Who Should Not Take the Flu Vaccine?

According to the CDC (Centers for Disease Control and Prevention), every individual above six months should take an annual flu vaccination. However, there are a few exceptions.

  • The people who should not take the flu shots are as follows:

  1. People who have life-threatening and severe allergic reactions to flu vaccine ingredients like antibiotics, gelatin, etc. However, people allergic to egg proteins can get the flu shot.

  2. Children who are younger than six months of age.

  3. People who have experienced severe allergic reactions to flu vaccines previously.

  • The people who should not take the nasal spray vaccine are as follows:

  1. People who are over 50 years of age.

  2. Pregnant women.

  3. People with severe allergic reactions to nasal spray vaccine ingredients other than egg proteins.

  4. Children below the age of two years.

  5. Individuals between the ages of two and 17 who take salicylate or Aspirin-containing medications.

  6. People who have had severe allergic reactions to any flu vaccine.

  7. Individuals with cochlear implants (an electronic device that improves hearing in individuals with moderate or severe hearing loss).

  8. Individuals who have taken influenza antiviral drugs in recent times.

  9. Children between the ages of two and four have a history of wheezing or asthma in the past year.

  10. People who have CSF (cerebrospinal fluid) leakage in the space surrounding the brain and nose, ear, throat, or any other region in the head.

  11. People with a weak immune system due to medications, HIV (human immunodeficiency virus) infection, or immune disorders.

  12. People who are in close contact with severely immunocompromised people.

Who Should Consult a Doctor Before Taking the Flu Vaccine?

  • Individuals who satisfy the below conditions should consult a doctor before taking the flu shots:

  1. People who are allergic to eggs or any ingredients in the vaccine.

  2. People with short-term or long-term sickness.

  3. People who have had severe allergic reactions to any flu vaccine previously.

  4. People with a history of Guillain-Barre syndrome.

  • Individuals who have any of the below-listed concerns should consult a doctor before taking the nasal spray vaccine:

  1. People with any kind of moderate or severe illness.

  2. People who are five years and above with a history of asthma.

  3. People who have Guillain-Barre syndrome after a dose of flu vaccine previously.

  4. People with certain medical conditions like kidney, lung, blood, heart, liver, neurologic, neuromuscular, or metabolic disorders like diabetes.

What Signs Should One Watch Out for After Receiving a Flu Vaccine?

The signs of concern after taking a flu vaccine may include behavioral changes, high fever, or severe allergic reactions. Any severe allergic reaction should be immediately consulted with a doctor. The signs of severe allergic reactions are as follows:

  • Paleness.

  • Weakness.

  • Fast heartbeat.

  • Dizziness.

  • Trouble breathing.

  • Hives (a raised, itchy area of skin).

  • Wheezing or hoarseness.

  • Swelling around the lips or eyes.


Flu shots are an effective and safe treatment with few side effects. Even though flu shots do not provide a guarantee against getting the flu, they help reduce the severity of the acquired illness. Generally, flu shots are safe for most people. However, people allergic to any vaccine ingredients or have other health conditions should consult a doctor and discuss with them before taking a flu shot.

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Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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