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Influenza Vaccines Only 42 Percent Effective in Adults This Year

doubting man

The influenza vaccines currently being administered in the United States are estimated by the U.S. Centers for Disease Control and Prevention (CDC) to be 42 percent effective in adults. This is an interim estimate for the 2023-2024 “flu season” published in the agency’s Morbidity and Mortality Weekly Report (MMWR) on Feb. 29, 2024.1 2 3

By “effective,” the CDC is referring to reducing the risk of influenza-related hospitalizations or “medically attended influenza virus infection,” not actually preventing influenza infections—notably influenza A (H1N1) and B (Victoria lineage).1 In its report, the agency stated:

These findings indicate that the 2023–24 seasonal influenza vaccine is effective at reducing the risk of influenza-associated outpatient visits and hospitalization.1

Less Than 25 Percent of Suspected ILI Cases are Influenza

Most influenza-like-illness (ILI) which occurs during the “flu season” is not actually caused by  type A or type B influenza. Studies show that less than 25 percent of suspected ILI cases turn out to be influenza after lab testing. There are many other respiratory infections that look like influenza but are caused by other types of viruses and bacteria.4

According to Sascha Ellington, PhD, leader of the CDC’s influenza prevention and control team, the 42 percent influenza vaccine effectiveness rate falls within the “range” that the CDC “typically” sees when the vaccine is a “good match with the [influenza] viruses that are circulating.” This season’s rate thus far lags behind the estimated 54 percent effectiveness rate for the flu shot in 2022-2023, but it is better than the 36 percent rate for 2021-2022.1 2 3 5 6

Influenza Vaccine Effectiveness Rate Under 50 Percent for Most Years

The 42 percent influenza vaccine effectiveness rate this year is roughly comparable to most annual rates during the past two decades. Since the 2004-2005 flu season, the CDC has estimated the flu shot to be more than 50 percent effective only five times—52 percent in 2006-2007, 56 percent in 2009-2010, 60 percent in 2010-2011, 52 percent in 2013-2014 and 54 percent in 2022-2023. In other words, the influenza vaccine the CDC recommends children and adults get every year has been more than 50 percent ineffective in preventing type A or type B influenza infections nearly three out of every four years.6 7

Influenza activity in the U.S. tends to peak in February and can last as late as May, although the CDC has noted that since the start of the COVID pandemic, the “timing and duration of influenza infection activity has been less predictable.” The CDC usually provides an estimate in June for the effectiveness of the influenza vaccine for the second half of the “flu season,” as well as an effectiveness estimate for the entire season.3 8

Nine Licensed Influenza Vaccines and All Contain Allergens

There are nine influenza vaccines that are licensed by the U.S. Food and Drug Administration (FDA) for distribution during the 2023-2024 flu season, including the Afluria Quadrivalent (produced by Sequris), Fluad Quadrivalent (Sequris), Fluarix Quadrivalent (GSK), Flublok Quadrivalent (Sanofi Pasteur), Flucelvax Quadrivalent (Sanofi Pasteur), FluLaval Quadrivalent (Sanofi Pasteur), FluMist Quadravalent (MedImmune), Fluzone Quadrivalent (Sanofi Pasteur) and Fluzone High-Dose Quadrivalent (Sanofi Pasteur).9

Each of these influenza vaccines contains at least one ingredient that is a potential allergen.

  • Alfuria contains the mercury-based preservative thimerosal (multiple-dose vials), egg protein, neomycin and polymyxin.
  • Fluad contains egg protein, kanamycin, neomycin and polysorbate 80.
  • Fluarix contains egg protein, gentamicin and polysorbate 80.
  • Flublok contains polysorbate 20.
  • Flucelvax contains thimerosal (multiple-dose vials) and polysorbate 80.
  • FluLaval contains egg protein and polysorbate 80.
  • FluMist contains egg protein, gentamicin, pork gelatin and monosodium glutamate (MSG).
  • Fluzone contains egg protein.
  • Fluzone High-Dose contains thimerosal (multiple-dose vials) and egg protein.9

 


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Click here to view References:
1 Frutos AM et al. Interim Estimates of 2023–24 Seasonal Influenza Vaccine Effectiveness — United States. MMWR Feb. 29, 2024; 73(8): 168–174.
2 Irwin L. CDC: Flu shots 42 percent effective this season, ‘consistent with past years’. The Hill Feb. 29, 2024.
3 Tin A. CDC finds flu shots 42% effective this season, better than some recent years. CBS News Feb. 29, 2024.
4 Thomas RE. Is influenza-like-illness a useful concept and an appropriate test of influenza vaccine effectiveness? Vaccine 2014; 32(19): 2143-2149.
5 U.S. Centers for Disease Control and Prevention. CDC Influenza Division. Nov. 2, 2023.
6 Armitage M. Does the Flu Shot Work? GoodRx Health Oct. 3, 2023.
7 Cáceres M. What’s So Effective About a Flu Vaccine That’s Less Than 10 Percent “Effective”? The Vaccine Reaction July 3, 2019.
8 CDC. Flu Season. Sept. 20, 2022.
9 Aungst C. Which Flu Shot Is the Most Effective for the 2023-2024 Flu Season? GoodRx Health Sept. 7, 2023.

14 Responses

  1. Why not say it takes 71 flu 💉 to prevent 1 flu.
    Than list the chance of a short term adverse reaction.
    The risk out weight the benefits for the pacent.
    You also didn’t mention formaldehyde used, or the long term risks. Vaccines cause pain and injury. Children with out vaccines are healthier.

  2. How do they know the effectiveness of any vaccine, let alone the flu shot, if they never run controls to compare vaxxed vs unvaxxed? All numbers are made up. As the article says, “This season’s rate thus far lags behind the ESTIMATED 54 percent effectiveness rate…” All guessing based on nothing.

  3. “……estimated by the U.S. Centers for Disease Control and Prevention (CDC) to be 42 percent effective…..”
    Well now, based on the integrity and honesty of the CDC in past years, allow me to discount their figure of 42% to approximately……………0.
    They actually are taking credit for those who got the vaccine and didn’t get the flu. Did their natural immunity prevent the flu or the vaccine ??
    Only the shadow knows !!!!

  4. #1 How could anybody possibly know how effective a vaccine is when we don’t have a clue how effective the unvaccinated immune system is before vaccination?
    #2 Maybe a terminology thing but isn’t the aluminum adjuvant in all vaccines considered a known allergen included to harshly activate the immune system?

    #1 >>>> If 40% 60% or 80% of unvaccinated subjects are exposed to the antigen which causes flu symptoms and don’t become symptomatic … then we have a baseline to work with

    1. More than an allergen. It is suspected of being a contributor to Alzheimer’s as the aluminum accumulates in the tissues and brain

  5. “Only 42%”? That is pretty high compared to the average in past years of 10% or less. It’s all total BS anyway.

  6. I think it would be more accurate to say the 2023/24 flu shots are 58% effective at spreading the flu!

  7. Thank you for the clear list of vaccine potential allergens. Your #9 indicator of a footnote did not include your sources. Please list sources in the future. Also explain vaccine metals?? Why is aluminum added and allowed? I’ve never seen an explanation.

    1. Why is aluminum in some vaccines?
      Aluminum salts are incorporated into some vaccine formulations as an adjuvant. An adjuvant is a substance added to some vaccines to enhance the immune response of vaccinated individuals. The aluminum salts in some FDA-approved vaccines are aluminum hydroxide, aluminum phosphate, alum (potassium aluminum sulfate), or mixed aluminum salts. For example: aluminum salts are used in DTaP vaccines, the pneumococcal conjugate vaccine, the HPV vaccine, and hepatitis B vaccines.

      Aluminum adjuvant containing vaccines have a demonstrated safety profile of over many decades of use and have only uncommonly been associated with severe local reactions. Of note, the most common source of exposure to aluminum is from eating food or drinking water.

      https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/common-ingredients-fda-approved-vaccines

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