Growing up as a kid I got the flu shot every fall, except for one. That one fall when I was six, my mom took me and my younger brother to the doctor to get the shot. I started screaming saying I didn’t want the shot. My mom pleaded with me, trying to convince me to allow the doctor to administer the shot. After about five minutes of being unsuccessful she finally gave up and said “Fine, but you’re going to get the flu and learn a lesson”. As mother’s usually are, she was spot on. The first week of February I started to come down with a little cold. Within 24 hours I was the sickest I’ve ever been, still to this day; I had the flu. For a week I could barely move, I was in bed all week with a raging fever and an unbearable headache. I learned my lesson, I have gotten the flu shot every year since and have not gotten the flu since. The discussion of immunizations possibly causing autism in class recently caused me to remember this topic, and come up with this question. How effective are flu shots in preventing the flu?

Photo from www.cooperclinic.com

The popularity of getting the flu shot has diminished significantly over the past ten years. According to an article written on healthimpactnews.com only forty percent of Americans received a flu shot in 2009. This was the year in which the “Swine flu” broke out nation wide. Last year still less than half of American adults received a flu shot, only forty seven percent. Additionally only three-quarters of children under the age of two received a shot to supposedly prevent the flu. These numbers shocked me, and forced me to question is getting the shot really beneficial (Health Impact).

According to the Centers for disease and health control (CDC) the flu vaccine reduces the risk of contracting the illness by between 50 and 60 percent. There are some factors that factor into this number like the age and general health of the patient, and the proximity between the type of flu virus and the type of flu vaccine. The benefits of the vaccine are most noticeable in young adults, and children over the age of two (CDC).

The null hypothesis is that flu shots are very effective in preventing the flu. So much so that every American should get one at least once annually, and that over half of American adults are doing themselves a disservice by not getting one no matter your age. The alternative hypothesis is that flu shots are not nearly as effective as many people seem to think, and consequently getting a flu shot . And, getting one is not a necessity and may vary depending on age. Reverse causation could be that people could get the flu due to receiving the shot. A confounding variable could be the patients overall health or age prior to receiving a shot. A file drawer problem is unlikely because the influenza virus is one of the most prominent viruses in the world, and statistics are recorded and analyzed on a annual basis. This is shown by the experiment I found that was run throughout the 2012-2013 flu season.

U.S public health officials ran an experiment throughout the 2012-2013 flu season to text the effectiveness of the flu shot for Americans. For the test, people with acute respiratory illness (ARI) over the age of six months were recruited. Of these people they were only eligible to take part in the test if the duration of their illness was less than or equal to seven days, and they had not received any form of anti-viral medication prior to enrollment in the experiment. 6,766 patients were enrolled in the case, although 314 were excluded from analysis due to unclear test results. Of the 6,452 who were tested, 2,877 patients or 45 percent of the patients had a flu shot more than two weeks before ARI symptoms appeared. Of the 2,877 vaccinated 795 or 28 percent were influenza virus positive. This is compared to 42 percent of the 3,575 who were not vaccinated becoming flu positive.  The effectiveness was seen least in adolescents aged 9-17, and patients over the age of 65. In both age groups, over 30 percent of patients vaccinated were still flu positive, 32 percent in those aged over 65, and 35 percent in those aged 9-17. Compared to the overall vaccine effectiveness of 49 percent the VE in those two age groups were 39 and 26 percent respectively. While the analysis of this study does not represent the views of the CDC, the experiment was supported by the CDC (NCBI) (Graph).

Overall, after seeing the results of this experiment I would reject the null hypothesis and therefore accept the alternative hypothesis. Flu shots are not as effective as I originally thought, and age does play a factor, even prior to the “elderly”. This topic could suffer from the Texas sharpshooter problem due to some data provided by the CDC that is partially ignored in the study.