Influenza Vaccine, Is It Effective?

When I was growing up, no one got a seasonal flu shot. It was unheard of. Now about 42% of adults and more than half of children get one:

All those flu shots. Is it doing anything?

The independent Cochrane Group, which does exhaustive reviews on a topic, had this to say about the effectiveness of the seasonal influenza vaccine (The evidence in this review is current to 31 December 2016.):

Vaccines to prevent influenza in healthy adults

Injected influenza vaccines probably have a small protective effect against influenza and ILI (moderate-certainty evidence), as 71 people would need to be vaccinated to avoid one influenza case. … Vaccination may have little or no appreciable effect on hospitalisations (low-certainty evidence) or number of working days lost.

Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence).

Fifteen included RCTs [randomized controlled trials] were industry funded (29%)

They said that a person’s risk of influenza, without a flu shot, is about 2.3% and that vaccination could reduce that to about 1%. The reason it feels like more than just 2% of people get the flu is that:

Over 200 viruses cause ILI [influenza-like illness], which produces the same symptoms (fever, headache, aches, pains, cough, and runny nose) as influenza.

And the flu shot doesn’t cover any of those 200 viruses.

Also, Cochrane says there’s a real problem with bias in these studies. Many are either industry-funded or lack information needed to determine industry’s influence. (“We were unable to determine the impact of bias on about 70% of the included studies due to insufficient reporting of details.”)

6 thoughts on “Influenza Vaccine, Is It Effective?

  1. Marj

    Not having had a flu vaccine for many years, a new doctor insisted that I have it which I did for three years. After the third one I developed a slow-spreading rash which lasted for about six months and was cured only by light treatments. Never again! I think my immune system revolted against what I suspect was the higher dosage shot. And too just driving around town the ever-present signage touting flu shots at not only drug stores but other places as well causes me to wonder about the motives.


    1. Bix Post author

      Well, rash is an immune system response. And people over 65 do get a higher dose shot:

      The high-dose vaccine contains four times as much flu virus antigen — the part of the vaccine that stimulates the immune system — as regular Fluzone and other standard flu vaccines.
      Mayo Clinic, Fluzone High-Dose: What distinguishes it from other flu vaccines?

      So it does sound like a complication of the shot.

      The last part of this Mayo Clinic article said:

      “The Food and Drug Administration accelerated its approval of Fluzone High-Dose on the condition that studies will continue to evaluate the new vaccine’s effect on seasonal flu outcomes, such as cases of flu and flu complications, in older adults. If, over the next few years, Fluzone High-Dose turns out to be superior to the regular flu vaccine by these measures, the high-dose vaccine may become the vaccine of choice for older adults.”

      I would not like to learn that pharmaceutical companies who sell the shot are doing the research.

      Upon Googling more … yes, Sanofi Pasteur Inc. who makes Fluzone is doing the research:
      Efficacy of High-Dose versus Standard-Dose Influenza Vaccine in Older Adults, New England Journal of Medicine, 2014


  2. Marj

    Many thanks for the interesting links re the high-dose vaccine. Agreed that the manufacturer also doing the research is troubling. Well, for now no more flu shots for me. My doctor is after me to have the pneumonia Prevnar 13 shot too and so far I’ve chickened out even so far as actually going to the pharmacy but leaving before getting it.


  3. Bix Post author

    I was just thinking … if your intervention (flu shot) reduces occurrence of flu from 2% to 1%, you could say that your intervention is 50% effective. Which sounds a lot better than it is. That’s really pushing it.


  4. Pingback: Deaths From Influenza Declined Over The 20th Century, It Wasn’t Because Of Vaccination | Fanatic Cook

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