Learn about the effectiveness of the flu vaccine

The flu vaccine provides protection against four common flu strains. Flu vaccines are 40%–60% effective when the most prevalent flu strains are matched to those in the vaccine.

In fact, flu vaccine effectiveness ranged from 29% to 48% in the five seasons leading up to 2020 to 2021. This means that annual vaccinations in recent years have reduced a person’s risk of contracting the flu by as much as 48%.

The vaccine also reduces the likelihood of serious illness, hospitalization and death. Therefore, the Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months and older get the flu vaccine (with very few exceptions).

Nine different flu vaccines are available for the 2021-2022 flu season. They all protect against the same four flu viruses. Here’s what you should know about flu vaccine effectiveness and types of flu vaccines.

2021-2022 Seasonal Influenza Vaccine Effectiveness

Each year, the flu vaccine is designed to protect against what scientists believe to be the most common strains of the flu virus. However, the effectiveness of the flu vaccine depends on which flu strains are most prevalent and how they compare to the strains the vaccine protects against.

Therefore, the effectiveness of the flu vaccine varies from year to year. Scientists do not yet have an estimate of the effectiveness of the flu vaccine for the 2021-2022 season. Additionally, during the 2020-2021 flu season, the CDC did not estimate the effectiveness of the vaccine due to historically low rates of influenza transmission, likely due to COVID-19 precautions that also protect against influenza.

You really need a flu shot this year, experts say

In past flu seasons

The CDC tracks the effectiveness of seasonal flu vaccines each year. In the past 17 years, the highest efficiency was in the 2010-2011 season, when the efficiency was 60%.

Here are the effective rates for the past five seasons for which data is available:

  • 2015-2016: 48%
  • 2016-2017: 40%
  • 2017-2018: 38%
  • 2018-2019: 29%
  • 2019-2020: 39%

Why are some flu seasons worse than others?

Reasons to consider getting the flu shot

A flu shot (flu shot or nasal spray) can significantly reduce the risk of getting the flu. Consider the 2019-2020 season: vaccinated people are 39% less likely to get the flu than unvaccinated people.

In addition to preventing disease, the flu shot also reduces the risk of hospitalization and death. Here are the researchers’ findings on the flu vaccine:

  • According to a 2021 study, vaccination reduces the risk of intensive care unit (ICU) hospitalization by 26% and reduces the risk of death by 31%.
  • Among adults hospitalized with the flu, vaccinated people were 59 percent less likely to require intensive care unit (ICU) care, according to a 2018 study.
  • Cardiac events are less likely to occur in vaccinated heart patients.
  • People with diabetes and chronic lung disease who were vaccinated were less likely to be hospitalized for these conditions.
  • Pregnant women who were vaccinated were 40 percent less likely to be hospitalized with the flu than those who were not vaccinated.
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In addition to protecting you, getting the flu shot can prevent you from getting the flu and passing it on to other people, including infants and the elderly, who are at higher risk for complications.

Pregnant women who are vaccinated help protect their babies from the flu (delivering protective antibodies produced by the vaccine), which can be valuable during the first six months when a child cannot be vaccinated.

Influenza Vaccine Efficacy Factors

There are many factors that affect the effectiveness of the annual flu vaccine. The most important thing is strain matching—whether the strain protected by the vaccine matches the most widespread flu strain in a given season.

In addition to vaccine construction, there are more personal factors that affect the effectiveness of vaccines.

Strain matching

To determine which strains are covered by the influenza vaccine, we collected data on influenza infection from around the world. Taking advantage of this, the World Health Organization (WHO) meets twice a year to decide which strains to focus on in vaccines.

For the northern hemisphere, the World Health Organization issued a recommendation in February. In the United States, the Food and Drug Administration (FDA) has the final say on which strains are included in vaccines.

Decisions about which strains to include are based on predictions made using past data. This provides time for vaccine production.

Vaccination time

The flu vaccine takes two weeks to work best. Therefore, the CDC recommends that everyone get the flu vaccine by September or October, before flu infections become common.

Getting vaccinated too late can expose you to an early infection with the flu. Vaccine protection, on the other hand, starts to wane after a few months. As a result, adults 65 years of age and older are usually not vaccinated early (in July or August).

The CDC recommends that people who have not been vaccinated in September or October get vaccinated (even late in the season) because the flu can spread throughout the spring.


In a given year, the protection afforded by the flu vaccine may vary by age as immunity changes over time, according to the CDC. There is no way to predict which age groups the flu vaccine will be most or least effective against in a given season.

Some studies suggest that vaccines that elicit a stronger immune response are best for people 65 and older. There are two vaccines approved for this population only: one containing a larger dose of the vaccine, and the other containing components that boost the immune response. Still, the CDC says older adults can get any type of flu shot.

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Vaccines rely on a person’s immune system to respond to the vaccine by producing antibodies, which are proteins that have a specific target, in this case against the influenza virus.

If a person has a compromised immune system due to a medical condition, they may not be able to generate the desired immune response, reducing the effectiveness of the vaccine. There are a variety of health conditions that can impair your immune system response.

This is one of the reasons why everyone should be vaccinated. By reducing the risk of catching and spreading the flu, they protect those who are immunocompromised and therefore cannot benefit from vaccination.

What does immunocompromised mean

Types of flu shots and vaccines

Nine flu vaccines (injection and nasal spray) are available for the 2021-2022 season. All nine protect against the same four types of flu.Because they can defend against four, they are called tetravalent vaccine.

The CDC doesn’t recommend one vaccine over another: the vaccine that’s available is the one you deserve. However, some people, including those under 2, those over 65, those with allergies or are pregnant, have special considerations and should discuss with their doctor which vaccine is best.

Adults 65 years and older

The CDC does not recommend specific vaccines for adults over the age of 65. However, some studies have shown that higher doses of vaccines or vaccines that use an adjuvant (a substance that boosts the body’s immune response to an antigen) can produce stronger immune responses that are more effective in this population. these are:

  • Fluad Quadrivalent: Uses one ingredient to elicit a stronger immune response and is approved for use in people 65 and older
  • Fluzone High Dose: Has a larger dose of antigen to generate a greater immune response and is approved for use in people 65 and older

if you are allergic

Many flu vaccines are made with eggs or egg protein, which poses an allergy risk for some people. The two egg-free vaccine options are:

  • Flublok Quadrivalent: Approved for those 18 and older
  • Flucelvax Quadrivalent: Approved for those 6 months and older

Is it safe for people with egg allergies to get the flu vaccine?

if you are pregnant

Pregnant women can get any flu vaccine Apart from For FluMist, it contains live virus.

What to know about getting the flu shot during pregnancy

Nasal Spray Options

FluMist Quadrivalent is a vaccine administered by nasal spray. It’s approved for people aged 2 to 49. However, it is the only vaccine that contains a live, weakened virus, and it should not be used by pregnant women or people who are immunocompromised. Talk to your healthcare provider about whether FluMist is safe for you.

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How the FluMist Nasal Flu Vaccine Works

baby flu vaccine

There are five flu vaccines approved for infants 6 months and older. they are:

  • Fluzone four price
  • FluLaval quad price
  • Fluarix Quad
  • Afluria Quadrivalent
  • Flucelvax Quadrivalent

Flu vaccine effectiveness over time

The flu vaccine takes two weeks to be fully effective, and protection is thought to last at least six months. But a person’s levels of antibodies to the vaccine decrease over time, and they may spread different strains of the flu.

Because of this, and each year the vaccine is tailored to the flu variants of the most concern, people should get an annual flu shot.

Flu vaccine side effects

Side effects from the flu shot are usually mild and go away without treatment after a few days. Common side effects include:

  • pain, redness, and swelling at the injection site
  • headache
  • fever
  • nausea
  • Muscle pain
  • fatigue

Allergic reactions are rare and usually occur within minutes after vaccination. Seek immediate medical attention if you experience swelling, fast heartbeat, or difficulty breathing. In rare cases (no more than one to two per million people who get the flu vaccine) a person can develop Guillain-Barre syndrome, an autoimmune disease.

Common side effects of the flu vaccine


The flu vaccine can prevent illness, hospitalization, and death. The CDC recommends that everyone 6 months and older be vaccinated annually (with very few exceptions). Vaccines vary in effectiveness because vaccines only protect against certain strains of the flu. In the past five years, flu vaccines have been between 29%–48% effective.

VigorTip words

Deciding whether to get vaccinated can be a big one. Although the flu is a common illness, it can be deadly, especially in people over the age of 65. The flu vaccine is not 100% effective, but it does significantly reduce the risk of illness, hospitalization and death.

If you have any questions about the vaccine, talk with your doctor about whether it is right for you or your child.

Frequently Asked Questions

  • When did the flu vaccine first appear?

    The flu vaccine was first available in the 1930s and became widely available in 1945.

  • Has the efficacy of flu vaccines improved since the 20th century?

    The effectiveness of the flu vaccine varies from year to year. It depends on how well the strains in the vaccine match the most prevalent strains in a given year.

  • Is it safe to get the flu and COVID-19 vaccine together?

    Yes, the CDC says you can get both the flu vaccine and the COVID-19 vaccine, including boosters.

    understand more:

    Get the flu and COVID vaccines together

  • What is the flu vaccine made of?

    Flu vaccines are made with killed or weakened flu viruses. These lenses also contain inactive ingredients, including preservatives.