The Influenza Vaccine: Questions Answered, Myths Dispelled

(This post was originally published January 22, 2014, and has been updated for the 2017-2018 influenza season.)

As the days grow colder the influenza vaccine rhetoric heats up, even at the most zen of locales, the yoga studio.  A few years ago I recall the discussion of who was ill and for how long infecting the air over the patchwork of exercise mats and the talk leading to a count of who got the flu vaccine, who did not, and the defense of their decisions. Back when I was a practicing physician assistant in Wisconsin, the misinformation about the flu vaccine was something I often addressed with my patients and the same rumor mill about getting a “jab” was alive and well years later and several states away in Colorado.  And a couple weeks ago while trolling Facebook, I stumbled upon a thread overflowing with emphatic “No ways!” to getting the flu vaccine, fueled by a barrage of all-too-familiar mythology.  While an interrupted savasana rattles the tenor of any devoted yogi’s day, misinformation disseminating on social media can cause far-flung harm. So on that note, let’s dispel some of those myths with some facts, “real news,” if you will.

First, let’s clear the air regarding flu terminology. When we discuss the “flu” we most often think of nausea, vomiting and diarrhea. But influenza, nicknamed the “flu,” is completely different. Influenza (at which the flu vaccine is directed) is a respiratory illness that produces many symptoms similar to those of the common cold*** but influenza and the common cold are caused by different types of viruses. Confused? Find yourself in good company…many people are. Which is likely why people are frustrated that they “got the flu vaccine and still got sick.” Simply put, coming down with a common cold or a stomach bug (neither of which is covered by any vaccine) does not mean the influenza vaccine was ineffective. “Flu” nomenclature is unnecessarily confusing, and the flu vaccine gets an unnecessarily bad rap. It’s an unfortunate lose-lose situation. (Of note: I will use “influenza” and “flu” interchangeably in the rest of this post, for simplicity’s sake.)

But are you guaranteed immunity from influenza if you get the vaccine? And if not, why get the vaccine in the first place? Both are valid questions. And both have answers. Every year there are three or four strains of influenza virus in the formulation of the trivalent and tetravalent vaccines, respectively. (However, some makers of flu vaccines are making the move to eliminate the trivalent vaccine in favor of the more-protective four-strain vaccine.) These strains are chosen based on what flu viruses are expected to be prominent during the upcoming flu season. The system by which this decision is made is not perfect, as we all know: experts become the victims of hindsight when deemed to have “picked wrong.”  Unfortunately, no one, not even those at the top of the infectious disease field, can see accurately into the future, year after year. But to address the question “Why get the vaccine in the first place if there is chance I’ll still get influenza?” the answer is straight forward:  getting the vaccine still revs up the immune system. So if by chance you are exposed to influenza and fall ill, your symptoms may not be as severe as they would if you were not immunized at all. Given that about 200,000 people are hospitalized for influenza yearly and the disease can be fatal to even the healthiest of individuals, why take a chance?

I could include many more facts about influenza in this post, but I decided to focus on addressing some of the more common misinformation. For more questions and details about influenza itself or the vaccine, the CDC website ( is excellent. Click on “Flu Basics” and you will find a wealth of easy-to-peruse information.


While we’re at it, let’s talk about some additional influenza vaccine issues for the current “flu” season:  

Flumist:  The intranasal form of the influenza vaccine was not recommended last year, and it is still not recommended for the 2017-2018 flu season, either.  Even though research conducted by the CDC determined that Flumist was not as effective at taming the flu, it is still approved by the FDA.  So if you prefer an “up-the-nose” dose of the influenza vaccine as opposed to a needle stick, and can find a health care provider who is offering it this year, you may receive it.  Just know that this intranasal form may not protect you as well from influenza as the injection will.  For more details, take a look at this link:

What’s up “Down Under”:  Australia has had a rough influenza season due to the influenza A strain H3N2, and as of August 18th, 2017, there have been more than double the number of cases of the flu and also twice the deaths as of the same time last year.  It’s widely accepted that the trend in OZ can indicate what we in the northern hemisphere can expect, experts are preparing for a nasty flu season here as well.  Translation:  get your kids and yourself vaccinated against influenza.  The vaccine, whether it contains three or four strains of influenza, will cover you against an H3N2 virus.


And a topic we can’t overlook in a discussion regarding the influenza vaccine:

The mercurial mercury issue:  A friend-of-a-friend on Facebook posted this reason for not getting a flu shot:  “The mercury (in the flu shot) causes cancer.”  Ok, there are so many things wrong with this statement.  For one, mercury is not known to cause cancer.  It is linked to dementia, tremors and kidney failure, among other health-related problems… but not cancer.  And thimerosal, the form of mercury (ethyl mercury) that acts as a preservative in the multi-dose vials of influenza vaccine, is not toxic to humans.  There is a substantial body of evidence that supports this.  However, methyl mercury, which is found in fish (ahi tuna and swordfish, for example), is toxic to the human nervous system when consumed in sufficient amounts.  In short, your seafood dinner is much, much more likely to contain toxic mercury than your flu shot (which doesn’t at all).  But if the idea of thimerosal in your vaccine still concerns you, ask for the single-dose injection; it is thimerosal/mercury-free.

***[The acronym FACTS, can help you sort out whether symptoms are related to the common cold or influenza: Fever, Aches, Chills, Tiredness and Sudden onset (of these symptoms) suggest the flu. However, this is a guideline and if you have any concerns at all, see your family’s physician.]

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