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I Got The Flu Shot And Now I Got The Flu!

by Eric Hall

August 17, 2013

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Donate Last week, I wrote about "zombie news" stories coming around on my social media timelines and how it serves only to spread misinformation. While watching these news stories pop up over and over, I also watched a Facebook discussion develop which included pretty much every standard logical fallacy regarding the flu vaccine. While I tried to insert a few facts in the discussion, it was a bit like shouting in a storm. So today, I want to address a few of the common fallacies in a (hopefully) succinct post.

I got the flu shot and now I got the flu!

This is one of the most common fallacies I hear when people decide not to get the flu shot. People either claim they never got sick until they got the shot, they got sick more often, or their sickness was worse after getting the shot. This is a perfect example of confirmation bias - correlating events because of their proximity in time. As defined in the Skeptics' Dictionary:
Confirmation bias refers to a type of selective thinking whereby one tends to notice and to look for what confirms one's beliefs, and to ignore, not look for, or undervalue the relevance of what contradicts one's beliefs. For example, if you believe that during a full moon there is an increase in admissions to the emergency room where you work, you will take notice of admissions during a full moon, but be inattentive to the moon when admissions occur during other nights of the month. A tendency to do this over time unjustifiably strengthens your belief in the relationship between the full moon and accidents and other lunar effects.
There are a few possibilities and several reasons one gets sick in a year where they received the flu shot. One possibility is they did indeed get the flu. Because of how the influenza virus works and how it is made, the strains aren't always perfectly matched. While even an imperfect match offers some protection, you may still contract the flu, albeit likely with milder symptoms. There is also a problem with low rates of vaccination, meaning the herd immunity is low, making the flu easier to spread.

Another possibility is you have something else. Many people mistake their symptoms as the flu. In reality, about 10-15% of "flu-like symptoms" are actually caused by the influenza virus. There are hundreds of cold viruses and bacteria which will give some of the same symptoms, especially the one where you just feel terrible. Unless a test is done and verified as the flu, there is no way to know if you actually have the influenza virus. Another illness is much more likely the cause when suffering what some believe to be multiple bouts with the flu.

Another different possibility with the flu shot is the idea that someone's first flu shot could make them more susceptible to getting the flu. It is an interesting thought given how the flu vaccine works and its low effectiveness when compared to other vaccines. Studies on the elderly show that the flu vaccine seems to only be effective when receiving the flu vaccine every year. In fact, morbidity in the elderly went up in the year following either their first flu shot or if they missed one after getting one for the previous five years. Morbidity was only reduced in the group who got a regular flu shot every year. The data has been repeated in more than one study. It would be great to study this in the population as a whole. It could make getting a regular flu shot that much more important.

My (relative/friend) is a (nurse/other healthcare worker) and never gets the flu shot!

This is one of the more hideous of the arguments against the flu shot. I almost want to ask the basic question if the health care worker believes in germ theory, because it is that basic. This is a basic logical fallacy known as the appeal to authority or argument from authority. The reason this logic fails is a person's authority alone is not enough to make a decision on a subject. The second requirement is a consensus of experts on the particular subject. A small number of health care workers don't believe in flu shots. A much larger number (and the data) show the flu shot to be valuable. This is why when a scientist writes a paper, there are dozens of citations to other science papers - to provide a framework of consensus on a topic.

Here's what the CDC's summary is on the research of flu vaccines and health care workers:
Health care workers who get vaccinated help to reduce the following:
  • transmission of influenza

  • staff illness and absenteeism

  • influenza-related illness and death, especially among people at increased risk for severe influenza illness

Higher vaccination levels among staff have been associated with a lower risk of nosocomial (hospital-acquired) influenza cases.

Influenza outbreaks in hospitals and long-term care facilities have been attributed to low influenza vaccination coverage among health care workers in those facilities.Higher influenza vaccination levels among health care workers can reduce influenza-related illness, and even deaths, in settings like nursing homes.
There are many stories of unvaccinated health care workers transmitting the flu. Look, for example, at number 10 in Mark Crislip's piece outlining several reasons for getting the flu shot. In fact, when you are done here - read his whole piece. It is exactly why everyone should get vaccinated.

It is surprising more health care facilities don't require vaccines. Those facilities requiring the vaccine, the rates are over 98%. The total average is 63.5%. If the science and stacks of data show vaccinated workers reduce the spread of the flu - it seems almost unbelievable it isn't required of every person working in health care able to get the vaccine.

The vaccine isn't that effective anyway

This has been covered quite extensively in the news after a large meta-study indeed showed the flu vaccine is only 62% effective. I say only, because most of the other vaccines we get as a child are well above 99% effective. But, the vaccine still helps. Even the authors of the very study that showed the vaccine to be 62% effective state:
"Our data strongly support that there can be a moderate level of protection from influenza vaccines," he said. "As an intervention goes, that's still an important level of protection."

As for the sparse evidence for benefits in people over 65 in particular, he observed that a study sponsored by Kaiser Permanente showed an 8% reduction in hospitalization in older people who were vaccinated, adding, "That would seem to be a good return on investment."

Kelley, his coauthor, commented, "For seniors, there's a reduction [in flu risk with vaccination] and it's greater than the reduction from a lot of other interventions in that age-group."
As Peter Lipson points out in his short Forbes piece, the other problem is how we measure effectiveness. Because not everyone with the flu gets tested, we can't be sure of the severity of everyone's symptoms from the actual flu. By many measures, the effectiveness is much higher, such as the important one of preventing deaths. That shouldn't be overlooked.

It is also true that the effectiveness varies from person to person. The very young and the elderly get less protection from the flu (see above as well about the elderly). This makes herd immunity that much more important - as well as research into better flu protections such as high dose vaccines.

Mark Crislip really nails it in his piece on flu vaccine efficacy. I quote him at length here:
In my mind that is the true benefit of the influenza vaccines: decreasing the morbidity and mortality of populations. The benefit for populations is derived through vaccinating individuals. That requires a bit of altruism on the part of those receiving the vaccine, as they may be getting vaccinated more for the benefit of others than for themselves. However, at least in the US, a premium is currently placed on being a self centered narcissist; indirectly helping others, even for MD's and RN's, is apparently not on the to do list. (emphasis mine - EH)

Do flu vaccines work? It depends on what the meaning of is is. If you are simplistic and like binary answers, yes or no, then you can pick yes or pick no, and find studies to support your contention that the vaccine doesn't work.

If you realize that medicine is subtle and nuanced, and often the answers are filled with qualifiers and uncertainty, that the practice of medicine is messy, I think the answer is that the flu vaccine is of benefit. And that the more people who get the vaccine, the greater the benefit for everyone.


I really don't know how to fight the madness when it comes to the flu vaccine. There are times it feels like there is no way to change someone's mind when it comes to the data or the importance of getting the shot not just to the individual, but to all of us. Talk to your doctor and make sure you can get the flu shot. If so, get the damn thing! You just might save someone's life.

by Eric Hall

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