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Flu shots - how they work and who should get them

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Updated on December 19, 2016

Winter is fast approaching and with that comes the onset of cold and flu season. While you can do your best to avoid falling victim to this year’s strain of flu by taking precautions (continuously washing your hands, avoiding touching your nose, ears, and eyes, avoiding close contact with those that are sick), getting sick is sometimes unavoidable. That’s where a flu vaccination can help. The shot, which is given via a needle, typically in the arm, protects against the most common influenza viruses that are circulating around this season.

Who should get a flu shot?

The Center for Disease Control (CDC) recommends that people over 6 months of age get an annual flu shot. While the shot is completely optional, the vaccination is recommended for people that are more likely to experience severe flu illness such as:

  • Young children
  • Adults over the age of 65
  • Pregnant women
  • People with chronic medical conditions and weakened immune systems

There are certain people that should refrain from getting the shot. These include:

  • Those with a history of Guillain-Barre syndrome
  • Anyone that has experienced an allergic reaction (such as a fever or moderate to severe illness at the time of vaccination) to a flu shot in the past
  • Infants under 6 months of age

People with an egg allergy should consult their doctor before getting the shot, as a tiny amount of egg protein is inside of the vial of several of the vaccination varieties. Typically people with egg sensitivities are able to get a shot, however.

When to get the vaccination

Seasonal flu shots usually become available in the fall. While some companies, such as CVS, start advertising for the flu shot earlier in the year, experts are now saying to wait till later in the year and closer to the season to get one. According to the CDC, antibodies created by the vaccination tend to decline in the months following when the shot is administered. So for this reason, some doctors are now suggesting that patients don’t go in for their shots until closer to the onset of flu season, which typically occurs between December and February. The shot typically takes about two weeks to take effect and start protecting you against influenza-causing viruses.

Flu shot options

There are two different types of flu shots – Trivalent and Quadrivalent. The Trivalent strain is said to protect patients against the three most common viruses that cause the illness, while the Quadrivalent protects against the same three, plus one additional variety. The Quadrivalent flu vaccination is not as widely available and tends to run higher in price but physicians such as Dr. Shilpi Agarwal, of One Medical Group, recommend opting for protection against the additional strain if it’s available and makes sense for you finally. There is also a high dose shot option available that contains four times the amount of antigens of the regular flu shot. This is recommended for adults ages 65 and older.

In addition to the shots, some companies are marketing the use of a flu mist in the form of a nasal spray vaccine. The CDC, however, has recently deemed this to be ineffective and recommends sticking with a traditional vaccination instead.

The different flu shot brands

The flu shot also comes in a variety of brands that patients can choose from, including:


  • Afluria, Fluarix, FluLaval, Fluvirin, Fluzone are brands of standard dose intramuscular trivalent. These are inactive vaccines that are grown in eggs. These are all available for ages 6 months and up. The inactive standard trivalent dose is the most popular influenza vaccination in the US.
  • Flucelvax is a standard dose intramuscular trivalent inactive vaccine that is grown via cell culture technology. It does not contain antibiotics or preservatives and is safe for adults ages 18 and older.
  • FluBlok is a recombinant intramuscular trivalent vaccine that is inactive and an egg-free option. This option is safe for adults ages 18 to 49 with egg allergies and is influenza vaccination that is egg-free, making it safe for those with egg allergies.
  • Fluzone Intradermal is a intradermal trivalent, inactive vaccine that is approved for adults ages 18 to 64.
  • Fluzone High-Dose is a high dose intramuscular trivalent, inactive vaccine, that is approved for adults ages 65 and up.
  • Quadrivalent
  • Fluarix Quadrivalent, FluLaval quadrivalent, Fluzone Quadrivalent are standard intramuscular quadrivalent, inactive vaccines, approved for ages 6 months and older.
  • Flumist Quadrivalent: This is a quadrivalent nasal spray, which is a live vaccination that is often used for children ages 2 to 8 and approved for use in patients ages 2 and up.

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Flu shot side effects

Side effects from the flu vaccination are typically minimal and most often include:

  • Soreness, redness, slight swelling, or warmth at injection site
  • A low grade fever
  • Decreased energy or fatigue
  • Headache

Consult your doctor immediately if you experience any of the following severe reactions:

  • Hives
  • Swelling
  • Difficulty breathing
  • An increased heart rate
  • Dizziness or weakness

Cost of the flu shot

The flu shot ranges in cost depending on where you get it done. Your doctor can perform it in his office and can bill it to your insurance, for instance, and places like CVS offer incentives such as 20% off your entire shopping cart if you get it done in store. Some retailers like Walgreens offer days where the shots are free and many local walk-in/urgent care clinics will charge around $10. County health departments typically offer the shot for free.

To give you an idea of the cost for the vaccination, here is a list of the current prices (without insurance) at several chain locations:

  • Costco: $14.99 (for standard trivalent)
  • CVS: $31.99 (for quadrivalent, ages 2-65), $51.99 (high dosage for age 65 and up)
  • Kmart: $27.99
  • Walgreens: $31.99 (trivalent), $39.99 (quadrivalent)
  • Rite Aid: $32.99 (trivalent), $39.99 (quadrivalent)
  • Meijer: $27.99 (trivalent), $50 (quadrivalent)
  • Wal-Mart: $27.88 (trivalent), $32.54 (quadrivalent)
  • Sam’s Club: $15 (trivalent), $25 (quadrivalent)
  • Kroger: $30 (trivalent), $40 (quadrivalent)
  • Target: $39.99 (quadrivalent)

Flu season can run from late November through early March and each year, 5% to 20% of Americans fall victim to the virus. Once you’ve caught the virus, it typically takes 1 to 4 days for symptoms (such as: fever, chills, muscle aches, headaches, fatigue, sore throat, cough, runny or stuff nose) to show up. A bout of the flu typically lasts anywhere from 1 to 2 weeks. If you’d like to opt for a vaccination this season to ward off the virus, heed the information above and select the type of shot and clinic location that works best for your budget.