In an interim report published on Mar. 11, 2022, the U.S. Centers for Disease Control and Prevention (CDC) estimates the effectiveness rate of the influenza vaccine at 16 percent during 2021-2022. The rate, which the CDC termed as “not statistically significant,” is based on a study involving 3,636 children, adolescents and adults in the United States from Oct. 4, 2021 to Feb. 12, 2022.1 2 3 4 5 6 According to the study researchers:
influenza vaccination did not significantly reduce the risk of outpatient medically attended illness with influenza A(H3N2) viruses that have predominated so far this season.6
This Year’s Influenza Vaccine ‘Basically Worthless’
The flu shot’s low rate of effectiveness “suggests that there was a mismatch between the strains of virus in the vaccine and what’s circulating,” said Jesse Goodman, MD, MPH, a professor and infectious disease specialist at Georgetown University’s School of Medicine. “It’s not ineffective, but it’s clearly suboptimal in its efficacy.”4
William Schaffner, MD, professor of preventive medicine at Vanderbilt University Medical Center, went further than that, characterizing this season’s flu shot as “essentially ineffective.”3 An article in Gizmodo put it more bluntly. Its headline read: “This Year’s Flu Vaccine Was Basically Worthless”.7
Dr. Schaffner added, “I can’t remember an ineffectiveness that was much lower than that.”2
In fact, the flu shot’s effectiveness rate did drop to 10 percent in 2004-2005.8
“We need to continue funding the research to create a better influenza vaccine,” Dr. Schaffner said. “Going forward, flu is going to continue to appear around the world and make annual epidemics that cause incredible amounts of illness, social and economic disruption, so we clearly need a better influenza vaccine.”2
Effectiveness of Annual Flu Shot Seldom More Than 50 Percent
The reality is that the estimated effectiveness rates for the annual flu shot are never high, seldom surpassing 50 percent and never surpassing 60 percent. The last time the effectiveness rate hit 60 percent was in 2010-2011. The effectiveness rate for the flu shot generally averages just over 40 percent, meaning that the vaccine is usually around 60 percent ineffective.8 9 10
During 2020-2021, the CDC did not estimate the flu shot’s effectiveness rate because of a lack of data due to low flu circulation that season. “Assessing [vaccine effectiveness] when there has been little flu circulating and in the midst of the COVID-19 pandemic is complicated and the estimates are not as rigorous as when there is more flu circulation,” noted CDC spokesperson Kristen Nordlund.2
During the previous five years, however, the vaccine’s effectiveness rates were pegged at 39 percent (2019-2020), 29 percent (2018-2019), 38 percent (2017-2018), 40 percent (2016-2017) and 48 percent (2015-2016). In 2014-2015, the effectiveness of the flu shot was estimated at 19 percent.9 10
Despite the often gross ineffectiveness of the flu shot, the CDC and many doctors continue to recommend getting it based on the rationale that it’s “better than nothing.” Paul E. Sax, MD of NEJM Journal Watch, for example, states:
We doctors, nurses, PAs, and pharmacists can be forgiven if the weak efficacy data might take some of the energy out of our annual recommendation. But let’s try to keep giving the vaccine.8
Perhaps this mindset is best highlighted by Egypt Galloway of Wilkes-Barre, PA, who notes, “I wouldn’t say the flu shots are a bad thing because nine times out of ten it doesn’t work.”8
Nine Influenza Vaccines Licensed in U.S.
The CDC lists nine influenza vaccines licensed for use in the U.S., and these vaccines, along with their ingredients taken directly from the manufacturer package inserts, are as follows:
- Influenza (Fluarix) Quadrivalent contains octoxynol-10 (TRITON X-100), α-tocopheryl hydrogen succinate, polysorbate 80 (Tween 80), hydrocortisone, gentamicin sulfate, ovalbumin, formaldehyde, sodium deoxycholate and sodium phosphate-buffered isotonic sodium chloride.
- Influenza (Flublok) Quadrivalent contains sodium chloride, monobasic sodium phosphate, dibasic sodium phosphate, polysorbate 20 (Tween 20), baculovirus and Spodoptera frugiperda cell proteins, baculovirus and cellular DNA and Triton X-10.
- Influenza (Flucelvax) Quadrivalent contains Madin Darby Canine Kidney (MDCK) cell protein, phosphate buffered saline, protein other than HA, MDCK cell DNA, polysorbate 80, cetyltrimethlyammonium bromide, and β-propiolactone and a mercury derivative known as thimerosal (multi-dose vials).
- Influenza (Flulaval) Quadrivalent contains ovalbumin, formaldehyde, sodium deoxycholate, α-tocopheryl hydrogen succinate, polysorbate 80 and phosphate-buffered saline solution.
- Influenza (Fluzone) Quadrivalent contains formaldehyde, egg protein, octylphenol ethoxylate (Triton X-100), sodium phosphate-buffered isotonic sodium chloride solution and mercury derivative thimerosal (multi-dose vials).
- Influenza (Fluzone) High-Dose contains egg protein, octylphenol ethoxylate (Triton X-100), sodium phosphate-buffered isotonic sodium chloride solution and formaldehyde.
- Influenza (FluMist) Quadrivalent contains monosodium glutamate, hydrolyzed porcine gelatin, arginine, sucrose, dibasic potassium phosphate, monobasic potassium phosphate, ovalbumin, gentamicin sulfate and ethylenediaminetetraacetic acid (EDTA).
- Influenza (Afluria) Quadrivalent contains sodium chloride, monobasic sodium phosphate, dibasic sodium phosphate, monobasic potassium phosphate, potassium chloride, calcium chloride, sodium taurodeoxycholate, ovalbumin, sucrose, neomycin sulfate, polymyxin B, betapropiolactone, hydrocortisone and mercury derivative thimerosal (multi-dose vials).
- Influenza (Fluad) Quadrivalent contains squalene, polysorbate 80, sorbitan trioleate, sodium citrate dihydrate, citric acid monohydrate, neomycin, kanamycin, hydrocortisone, egg protein and formaldehyde.11
Additional information about influenza and influenza vaccines, including complete copies of influenza vaccine package inserts that also list contraindications, reported reactions, results of pre-licensure clinical trials and other facts, can be found on NVIC.org.
If you would like to receive an e-mail notice of the most recent articles published in The Vaccine Reaction each week, click here.
Click here to view References:
1 Bean M. Flu shot offers little protection this season, CDC data shows. Becker’s Hospital Review Mar. 11, 2022.
2 Christensen J. This season’s flu vaccine seems to be a poor match, early CDC data shows, but it’s been a mild flu season. CNN Mar. 10, 2022.
3 Lovelace B. This season’s flu vaccine was a poor match for the virus, CDC reports. NBC News Mar. 10, 2022.
4 Lukpat A. Flu Vaccine Was Not Very Effective This Season, the C.D.C. Says. The New York Times Mar. 10, 2022.
5 Shaheen M. Latest flu vaccine was INEFFECTIVE during the 2021-2022 season and was deemed a ‘poor match’ to the strain, CDC report finds. Daily Mail Mar. 10, 2022.
6 U.S. Centers for Disease Control and Prevention. Interim Estimates of 2021–22 Seasonal Influenza Vaccine Effectiveness — United States, February 2022. Morbidity and Mortality Weekly Report Mar. 11, 2022.
7 Cara E. This Year’s Flu Vaccine Was Basically Worthless. Gizmodo Mar. 11, 2022.
8 Cáceres M. Influenza Vaccine Effectiveness a ‘Dismal 10 Percent’. The Vaccine Reaction Jan. 2, 2018.
9 Burch K. Understanding Flu Vaccine Effectiveness. Verywell Health Jan. 26, 2022.
10 CDC. CDC Seasonal Flu Vaccine Effectiveness Studies. Mar. 11, 2022.
11 CDC. Vaccine Excipient Summary.