During Past Flu Seasons
The CDC tracks seasonal flu vaccine effectiveness each year. Over the past 17 years, the highest effectiveness was in the 2010-2011 season when it was 60% effective.
Here are the effectiveness rates over the past five seasons for which data are available:
- 20152016: 48%
Flu Vaccine And Covid
Flu vaccination is important because:
- more people are likely to get flu this winter as fewer people will have built up natural immunity to it during the COVID-19 pandemic
- if you get flu and COVID-19 at the same time, research shows you’re more likely to be seriously ill
- getting vaccinated against flu and COVID-19 will provide protection for you and those around you for both these serious illnesses
Can The Flu Shot Help Prevent Covid
According to the CDC and FDA, the flu shot cannot prevent you from getting COVID-19 or any of its variants, including the Delta variant. The flu and COVID-19 are two different viruses despite the number of symptoms they share. However, getting the flu shot may help your doctor rule out the flu in the event you become ill and start exhibiting symptoms similar to both the flu and COVID-19. Getting the flu shot can also help you avoid hospitalization and severe illness, which can free up room for those who need treatment for COVID-19.
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When Should People Get The Flu Vaccine
Flu season runs from October to May. It’s best to get a flu vaccine as early in the season as possible, ideally by the end of October. This gives the body a chance to make antibodies that protect from the flu. But getting a flu vaccine later in the season is better than not getting it at all. Getting a missed flu vaccine late in the season is especially important for people who travel. That’s because the flu can be active around the globe from April to September.
Severely Immunocompromised Persons Receiving Live Vaccines

Live vaccine viruses are attenuated so they do not cause infection in individuals with intact immune systems. Live vaccines, however, are contraindicated for people who are severely immunocompromised since their weakened immune systems may result in the live vaccine causing illness. Two published case reports describe immunocompromised children who received varicella vaccine, and where vaccine strain varicella zoster virus infection contributed to their deaths . In one case, a 4-year-old child who had been in complete remission from acute lymphoblastic leukemia for 5 months received varicella vaccine during a 2-week break from chemotherapy in the other case, a 15-month-old did not have a diagnosis of being immunocompromised, but had failure to thrive and several hospitalizations beginning at 5 months of age for infections and respiratory problems requiring steroid treatment , indicating a possible undiagnosed immunodeficiency. There are at least six case reports of death among severely immunocompromised persons that have been linked to vaccine strain measles virus infection , including a case of vaccine associated pneumonitis in an immunocompromised person with HIV and a case of measles inclusion-body encephalitis in a 21-month-old child with primary immunodeficiency . CDC recommends screening prior to vaccination so that contraindications and precautions, including previously diagnosed immune system problems are identified .
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Flu Vaccine Side Effects
Side effects of the flu vaccine are usually mild and go away without treatment in a few days. Common side effects include:
- Soreness, redness, and swelling where the shot was given
- Headache
- Muscle aches
- Fatigue
Rarely, allergic reactions occur, often within minutes of the vaccine being administered. If you experience swelling, racing heart or trouble breathing, seek medical attention immediately. Extremely rarely a person may develop Guillain-Barré syndrome, an autoimmune disease.
Complications From Smallpox Vaccine
Serious adverse reactions and complications from smallpox vaccine can result in death in rare cases . Based on historical data, the death rate following smallpox vaccination is approximately one death per million persons receiving an initial dose and one death per four million among persons receiving another dose after the first dose . Death has also occurred among non-vaccinated persons who had accidental contact with vaccination sites of vaccine recipients . Reactions that can cause or contribute to death include eczema vaccinatum, progressive vaccinia, postvaccinal encephalitis, myocarditis, and dilated cardiomyopathy. Additionally, vaccination of pregnant women can cause fetal infection resulting in stillbirth or infant death . Patients should be carefully screened for precautions and contraindications prior to receipt of smallpox vaccine . In 2008, a new smallpox vaccine, ACAM2000 replaced the previously used vaccine Dryvax®. The data indicate that ACAM2000 has a similar safety profile to Dryvax® . Naturally occurring smallpox disease has been eliminated worldwide, and in the United States, smallpox vaccine is currently only given to military personnel and selected individuals that might be at high risk of exposure, such as laboratory scientists that work with smallpox or similar viruses .
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People Who Should Avoid Getting Flu Shots:
Flu shots have many benefits, but for a few patients, these benefits are out-weighted be potential harmful reactions. Vaccines for flu are usually not advised for the following patients:
- Patients who have experienced allergies when they had their previous vaccines
- Patients who have a weaker immune system, cannot handle the stimuli of antibodies
- Children below two years or infants
- Pregnant women
It is important to consult a medical doctor before having a flu shot.
Trivalent And Quadrivalent Shots Made With Adjuvant
These shots, called Fluad and Fluad Quadrivalent, are another option for flu vaccines that are approved for people ages 65 and older. It includes an ingredient called adjuvant, which also creates a stronger immune system response.
These flu vaccines are slightly different because they protect against four different strains of the flu virus .
Because of this, these vaccinations can provide broader protection from infection.
Options are below.
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Why Are There So Many Vaccines In Development
Typically, many vaccine candidates will be evaluated before any are found to be both safe and effective. For example, of all the vaccines that are studied in the lab and laboratory animals, roughly 7 out of every 100 will be considered good enough to move into clinical trials in humans. Of the vaccines that do make it to clinical trials, just one in five is successful. Having lots of different vaccines in development increases the chances that there will be one or more successful vaccines that will be shown to be safe and efficacious for the intended prioritized populations.
Myth #: It Contains Thimerosal Which May Be Harmful
Thimerosal a preservative that contains mercury has never been shown to be harmful, Cunningham said. The type of mercury linked with nervous system damage is methyl mercury, he said. Concerns over levels of methyl have led to recommendations that pregnant women avoid eating large amounts of certain types of fish, such as swordfish.
In contrast, thimerosal is an ethyl mercury compound.
Still, because the preservative raised controversy, especially over a now-disproven link to autism, it was taken out of almost all U.S. vaccines starting in 2001, Cunningham said.
The injectable form of the flu vaccine is available to health care providers as large, multidose bottles and small vials carrying individual doses. A tiny amount of thimerosal is added to the multidose bottles to ensure that no bacteria will grow in the vaccine, Cunningham said. The individual-dose bottles contain no thimerosal.
The nasal spray form of the flu vaccine also contains no thimerosal, he noted.
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Which Flu Vaccine Is The Most Effective
When flu vaccines are being produced, the strains included are standardized by the FDA. Each 2021-2022 vaccine includes:
-
Two type B viruses
This means that no matter what vaccine you choose, youre being protected against the same strains. Flu vaccines are typically between 40% and 60% effective from year to year. But when it comes to picking the right flu vaccine for you, you have to take other factors into account.
Side Effects Of The Flu Vaccine

Similar to other types of vaccinations, theres a risk of side effects with the flu shot. Common side effects may include tenderness or redness at the injection site.
In addition, some people experience mild flu-like symptoms for 1 to 2 days after vaccination. This can include weakness, body aches, or a fever, but this isnt the flu.
You might have issues if youre severely allergic to eggs or another ingredient in the vaccine.
Signs of a serious reaction include:
- breathing difficulty
- dizziness
Life threatening allergic reactions are rare after getting the flu shot, though.
Symptoms of a reaction occur within a few hours of vaccination. If you do have symptoms of an allergic reaction, seek immediate medical attention.
The CDC recommends people with an egg allergy still get a flu shot. If you have a severe egg allergy, you may consider getting your flu shot in a medical setting that can treat allergic reactions. You can also request a vaccine that doesnt contain egg protein.
You may have to avoid vaccination if youre allergic to another ingredient in the vaccine.
In rare cases, Guillain-Barré syndrome may develop within days or weeks of a vaccination.
Guillain- Barré syndrome is a neurological disorder where the bodys immune system attacks the peripheral nervous system. This condition can cause muscle weakness and paralysis.
Among those who receive a vaccination, theres only
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Special Consideration Regarding Egg Allergy
People with egg allergies can receive any licensed, recommended age-appropriate influenza vaccine that is otherwise appropriate. People who have a history of severe egg allergy should be vaccinated in a medical setting, supervised by a health care provider who is able to recognize and manage severe allergic reactions. Two completely egg-free flu vaccine options are available: quadrivalent recombinant vaccine and quadrivalent cell-based vaccine.
Coming To A Drug Store Near You: Mrna Flu Vaccines
The same mRNA technology that gave us effective COVID-19 vaccines could yield a new generation of highly protective seasonal flu shots. When will we see these upgraded influenza vaccines? Perhaps sooner than you think.
The rapid development of mRNA-based COVID vaccines has sparked fresh interest in earlier efforts to produce new and hopefully more effective flu shots with the same technology. Pfizer, Moderna, and Sanofi/Translate Bio each have an mRNA flu vaccine in clinical trials, and there are ten more candidates awaiting testing.
It’s one thing to test a drug and quite another to commercialize it. The question, then, is will these next-generation flu shots be available any time soon? The answer is yes, perhaps as soon as 2022. There are no guarantees when it comes to drug development, but here’s what we know so far and why better flu shots are necessary.
The case for new flu vaccines
A found that the recombinant vaccine may provide better protection, measured as antibody-mediated immunity against HA, compared to its egg- and cell-based counterparts, though none of the shots were especially impressive. The CDC couldn’t give an estimate for 2020-2021 because of low influenza virus circulation, but vaccine efficacy was just 39 percent in the 2019-2020 flu season.
mRNA to the rescue?
Coming soon?
Public acceptance
Emphasis on relatively. Getting the FDA to approve any drug is no picnic.
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What To Know About Double Mutant Covid
But viruses acquiring mutations isn’t “necessarily a bad thing,” Jasmine Plummer, Ph.D., associate director of applied genomics at Cedars-Sinai medical center in Los Angeles, told TODAY.
” want to survive,” she explained. “It’s not in best benefit to keep killing the host, meaning the person. Near the end, figure out a way … to survive by infecting more people, but the outcome of that infection is hopefully not as severe.”
What Flu Vaccines Are Available Via Jet Injector This Season
One flu vaccine, AFLURIA Quadrivalent®, is approved for use with a jet injector this season. AFLURIA Quadrivalent® flu vaccine provides protection against an influenza A virus, and influenza A virus and two influenza B viruses. For more information, see What You Should Know for the 2021-2022 Season.
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Myth #: The Flu Isn’t Serious
“The flu is certainly a very serious disease,” Cunningham said.
Every year, between 15 million and 60 million cases of the flu are reported in the U.S., Cunningham said. More than 200,000 people with the flu are admitted to hospitals yearly. And between 3,000 and 50,000 people in the U.S. die of the flu yearly. During the 2019-2020 flu season, early estimates by the CDC suggest 38 million Americans were infected with the flu and 22,000 people died from it.
One reason people may not perceive the flu as being serious is that cases of the “stomach flu” are mistaken for influenza virus infections. “True influenza is an infection of the lungs and respiratory tract,” Cunningham said. Infected people may develop a high fever, body aches and nasal congestion, he said.
People with the stomach flu which is commonly caused by a virus called norovirus have diarrhea, cramping and other gastrointestinal symptoms. Influenza does not cause such symptoms.
This article is for informational purposes only, and is not meant to offer medical advice.
Originally published on Live Science.
Rachael has been with Live Science since 2010. She has a master’s degree in journalism from New York University’s Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.
Where Can I Get A Flu Shot
There are more places than ever to get your flu vaccination. Doctorsâ offices, clinics, and health departments offer the flu shot but you may need to make an appointment in advance. Pharmacies have become an easy and convenient option to get your flu shot. At Walgreens, we offer flu shots whenever a pharmacist is on duty. Walk-ins are welcome, but if you’d prefer, you can make an appointment online. Find a location near you to ask about vaccine availability or schedule an appointment online.
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What Is The Difference Between Fluzone High
Fluzone High-Dose Quadrivalent contains four times the antigen, the part of the vaccine that helps your body build up protection against flu viruses, than Fluzone Quadrivalent and other standard-dose inactivated flu vaccines. The higher dose of antigen in the vaccine is intended to give people 65 years and older a better immune response to vaccination, and therefore, better protection against flu. Both Fluzone High-Dose and Fluzone Quadrivalent are produced by the same manufacturer and are quadrivalent vaccines. There are a number of other flu vaccines produced by other manufacturers.
Are Quadrivalent Flu Vaccines Safe

Yes. Flu vaccines that protect against four flu viruses have a safety profile similar to seasonal flu vaccines made to protect against three viruses, with similarmostly mildside effects. Like all seasonal flu vaccines, vaccines that protect against four flu viruses are monitored annually for their safety and effectiveness.
Quadrivalent vaccine cannot cause flu illness because they contain inactivated virus, attenuated virus, or are made using recombinant methods that dont use flu virus in the manufacturing process.
For information about flu vaccine side effects, see Can the flu vaccine give me the flu?
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Are There Benefits Of Fluzone High
Data from clinical trials comparing Fluzone to Fluzone High-Dose among people 65 years and older indicated that a stronger immune response occured after vaccination with Fluzone High-Dose. A study published in the New England Journal of Medicineexternal icon indicated that the high-dose vaccine was 24% more effective in preventing flu in adults 65 years and older relative to a standard-dose vaccine. Another study published in The Lancet Respiratory Medicineexternal icon reported that people 65 years and older who got Fluzone High-dose had a lower risk of hospital admission compared with people in that age group who got the standard-dose Fluzone, especially those living in long-term care facilities. This study was conducted during the 2013-14 flu season among more than 38,000 resident of 823 nursing homes in 38 states.
For the 2021-22 season, all Fluzone High-Dose vaccine will be quadrivalent. Data comparing the effectiveness of Fluzone High-Dose Quadrivalent with standard-dose inactivated quadrivalent vaccines are not yet available.
How Long Does The Flu Shot Last
The flu shot can help protect you and your family from the flu for the duration of the current years flu season. Getting a flu shot every year is important, as there are new and different flu strains that come into circulation every year. If you get the flu shot in September, the vaccine can protect you well until the end of flu season, which can last for up to 8 months according to the FDA.
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What If I Have An Egg Allergy
Most flu shots and the nasal spray flu vaccine are made using egg-based technology, and may contain a small amount of egg proteins. However, studies show that severe allergic reactions to the flu shot and nasal spray vaccine are unlikely in people with egg allergies. People who have experienced only hives after exposure to eggs can receive any influenza vaccine. If eggs have given you serious allergic reactions, meaning any symptom other than hives, you can still receive any of the available influenza vaccines but you should receive it in a health care provider’s office, hospital, clinic, or health department under the supervision of a health care provider who can recognize and manage severe allergic reactions. Your provider may recommend that you receive the egg-free influenza vaccine.