When it comes to small creatures, people always say, “It is more scared of you than you are of it.” I suppose that is mostly true, with the flu a clear exception to this assumption. The flu is a teeny, tiny virus only visible only through an electron microscope and relies on a host cell to live and multiply. It is hard to imagine that something so small can cause complications so big. But, alas, the flu is a public health problem of epic proportions, and, if you’ve ever had the flu, you also know it is a personal health problem of epic proportions.

Despite my yearly inoculations, I have had the flu on several occasions (my worst bout of the flu once caused me to miss my season opener at the Ironman 70.3 Oceanside). While my general ability to endure discomfort unfortunately has been nurtured by years of injuries and chronic pain, the flu, on the hand, has reduced me to sniveling and hiding under the covers, curled up in the fetal position, waiting for the body aches, fever and chills to pass. The flu is a menace.

What is the flu shot?

There is an imperfect means of prevention for the flu: the infamous flu shot. The flu vaccine was developed to prevent two main types of flu: influenza A and influenza B.[1] Usually, the flu vaccine is trivalent but now there is a quadrivalent option, meaning it can protect against three or four strains of the influenza viruses.[2]

Each season the flu vaccine is prepared based on the type of flu that is predicted for a particular year, so the shot changes from year to year. The efficacy of the shot for actually preventing the flu also varies, with protection ranging from 70-90%, hence my getting the flu despite vaccinations. Adding to the complexity of the flu shot is the fact that immunity only lasts for a year, requiring re-immunization every season.

Who should get the flu shot?

The CDC recommendation states that “everyone six months and older should get a flu vaccine every year by the end of October, if possible. However, getting vaccinated later is OK. Vaccination should continue throughout the flu season, even in January or later.” There are only very few medical reasons to not get the shot, such as a previous severe reaction to the flu shot.

Uptake of the flu vaccine by a large percentage of the population creates something called herd-immunity. Herd-immunity occurs when a large enough percentage of the population is protected against a disease through immunization, thereby protecting those who are unable to get a vaccination. Herd-immunity greatly decreases the risk of an outbreak.

In order for herd-immunity to occur for the flu, 80% of healthy individuals and 90% of at-risk individuals (i.e. very young, elderly, immune-compromised, asthmatics) need vaccinations, but these percentages have not yet been met in the US.[3] Herd-immunity is particularly important among athletes considering the amount of time spent in close quarters with others in places like work, the gym, training sessions and races.

I spoke to Dr. Robert Zeiger, an allergist and my “esteemed” father, about the flu vaccine. He explained, “An athlete with a history of asthma or other chronic respiratory disease is at high-risk for influenza complications and will benefit most with flu immunization. These high-risk individuals are more susceptible to asthma exacerbations and secondary pneumonia. The benefits of influenza immunization far outweigh the infrequent downsides.”

What are the infrequent downsides? According to Dr. Bob, there can be soreness or irritation from the shot, getting the flu anyway due to the incomplete identification of the virus-of-the-year, and very rarely, neurologic complications.

Why should athletes in particular get the flu shot?

Athletes are often on the fence about whether they should get a flu shot, and consequently, only about 30% getting the flu shot — far below the target needed for herd-immunity.[4] Misinformation about the flu shot often drives the ambivalence (no, the flu shot cannot give you the flu). There also is uncertainty about when to get the shot, whether the shot itself makes you sick, and the whole debate about vaccines in general.

Almost everyone should get the flu shot (as noted above), but athletes are a “high-risk” group who should consider the benefits of the flu shot before skipping it altogether. What makes athletes particularly at-risk for getting the flu? Habits and behaviors like more frequent air travel than non-athletes, increased close contact with others through sport and are more likely to share objects like water bottles, which can act as disease vectors.”[5]

Besides the everyday implications of being an athlete, there is the more serious side-effect of being an athlete, namely reduced immune function.[6] Heavy exertion has both acute and chronic effects on immune function, with the risk of upper respiratory tract infections increasing during heavy bouts of training and in the one to two weeks following competition.[7]

For an athlete, the flu can mean weeks of missed training, which is huge inconvenience if you are training for something like the Boston Marathon or Ironman 70.3 Texas. Since autumn is such a popular timeframe for big marathons like Bank of America Chicago Marathon, Medtronic Twin Cities Marathon and Rock ‘n’ Roll Las Vegas Marathon, a case of flu can be especially heartbreaking if it means you have to miss one of these marquee events.

In short, general consensus by public health authorities, as well as studies specific to athletes as a group, indicate that athletes should receive a quadrivalent intramuscular or intradermal vaccination.[8] It takes 1-2 weeks for full immunity, so plan accordingly with your race schedule. October is a good time to get the flu shot, but if you’re registered to run the TCS NYC Marathon on November 6, you might want to consider getting one even earlier.

Dr. Bob is unabashed about his thoughts on the flu shot (hence his barrage of phone calls this time of year “gently” reminding me to obtain said shot), and his final piece of advice is, “Should an athlete unwisely elect not to get the flu shot, remember that there are antiviral oral medications that can be taken during outbreaks to help protect oneself. However, vaccination supersedes medication for prevention.”

Many primary care physicians, other healthcare providers, and even your neighborhood drugstore offer the flu shot, but you can also use the CDC’s Vaccine Finder to find the nearest location to get yours.

[1] Trabacchi, V., Odone, A., Lillo, L., Pasquarella, C., & Signorelli, C. (2015). Immunization practices in athletes. Acta Bio Medica Atenei Parmensis86(2), 181-188.

[2] Ibid.

[3] Plans-Rubió, P. (2012). The vaccination coverage required to establish herd immunity against influenza viruses. Preventive medicine55(1), 72-77.

[4] Lautermilch, J., & Doyle-Baker, P. (2014). The athlete and the flu vaccine: Melodrama, common sense or ignorance?. Journal of Science and Medicine in Sport18, e54.

[5] Ibid.

[6] Nieman, D. C. (2000). Exercise effects on systemic immunity. Immunology and Cell Biology78(5), 496-501.

[7] Ibid.

[8] Gärtner, B. C., & Meyer, T. (2014). Vaccination in elite athletes. Sports Medicine44(10), 1361-1376.

Joanna ZeigerJoanna Zeiger, MS, PhD, raced as a professional triathlete from 1998-2010. She placed fourth in the triathlon at the 2000 Sydney Olympics and won the 2008 IRONMAN 70.3 World Championships. She is a seven-time Olympic trials qualifier in three sports — marathon, triathlon and swimming. Joanna still pursues her passion for sports as a top Masters runner. Through her company, Race Ready Coaching, Joanna trains endurance athletes to reach their personal best and instills in them the importance of having fun even when they are training hard. When she is not coaching or training for running events, Joanna works as a consultant in the field of biostatistics. Joanna’s book The Champion Mindset: An Athlete’s Guide to Mental Toughness will be published in February 2017 by St. Martin’s Press.


  1. For decades I got the mandatory flu shot in the military. It never made a difference. Some years I got the flu some years not. Same as now when I don’t get the shot. It’s a crap shoot

  2. That is really interesting that flu shots are recommended to get every year. Maybe I should look into getting my flu shot every year so that I can do my best to remain healthy. That is something I should have done for my kids every year as well.


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