This last week as I was driving to work, I noticed it again. They were everywhere. Every drugstore I passed had a sign telling you to get your flu shot. And to tell you the truth, it makes me roll my eyes. Now if you didn’t know, I am not real big on vaccinations in the first place, and the flu vaccine I feel is especially a waste of time and money. Today I wanted to share with you some of the research about the flu vaccines and some of the ‘statistics’ that are thrown around as to why you should get a flu vaccine.
To start with, why are you told to get a flu vaccine? Usually it is to prevent you from getting the flu and you could die from the flu. While it is true that you can die from the flu, what is the number that you usually hear on flu deaths? The official estimates by the CDC are actually a range from 3,000 to 49,000 for “seasonal influenza-associated deaths in the US.” These are some pretty significant numbers. How did they come up with that range? Well, this is the range for flu-associated deaths from the 1976-1977 to the 2006-2007 flu seasons. But you may be wondering what are influenza-associated deaths? You see often the flu is not really the direct cause of death but death occurs from a secondary infection that leads to pneumonia or other respiratory or circulatory problems because of the flu. So basically they use statistical models to estimate the number of influenza-associated deaths because the actual numbers are not really known. But one of the interesting things that is found on the CDC website is “about 90% of influenza associated deaths occur among adults 65 years and older.” So the elderly are the most at risk of dying from complications from influenza, which makes sense because they have the most circulatory and respiratory problems. But who is at the most risk for death and complications is an important fact to remember.
Now getting the flu is not fun, but I think the many people consider a flu shot because of the possibility of flu being fatal or leading to complications that can be fatal. So what does the research say about the effectiveness of the flu shot? In a Cochrane Review “Vaccines for preventing influenza in the elderly” there should be some good evidence to back up the universal recommendation to vaccinate the elderly. Well what they found is that there was only one randomized controlled trial “assessing efficacy and effectiveness. Although this seemed to show an effect against influenza symptoms it was underpowered to detect any effect on complications.” And the overall conclusion: “The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines for people aged 65 years or older.” So basically there is insufficient evidence to conclude that the flu vaccine helps prevent complications or even the flu for that matter in people 65 years and older!
So what about the effectiveness of the flu shot in other groups of people? Well the Cochrane Review “Vaccines for preventing influenza in healthy adults” looked at studies assessing the flu vaccine in healthy adults. The review contains this nice little warning:
This review includes 15 out of 36 trials funded by industry (four had no funding declaration). An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in light of this finding.
So in light of that what did they find? “[U]nder ideal conditions (vaccine completely matching circulating viral configuration) 33 healthy adults need to be vaccinated to avoid one set of influenza symptoms.” So what about under non-ideal conditions? “In average conditions (partially matching vaccine) 100 people need to be vaccinated to avoid one set of influenza symptoms.” They also found “Vaccine use did not affect the number of people hospitalised or working days lost but caused one case of Guillian-Barré syndrome (a major neurological condition leading to paralysis) for every one million vaccinations.”
To be completely fair, there was a reduction in flu symptoms in those vaccinated compared to those who were unvaccinated. When the vaccine matched the viral circulating strain and there was high circulation, “4% of unvaccinated people versus 1% of vaccinated people developed influenza symptoms,” but when there was poor matching of vaccine to flu strains the numbers were 2% of unvaccinated people versus 1% of vaccinated people developed influenza symptoms. But again those results need to be interpreted in light of the warning mentioned above. But if you are a healthy adult is having a 1-3% lower risk of getting flu symptoms and no difference in complications worth the shot? That is a question you need to answer for yourself.
In closing there is much more I could say on the subject and I may in another blog post. But I will say that there are other things besides getting a flu vaccination that will improve your odds of not getting the flu. They are common sense things like washing your hands, eating healthy, and getting adequate sleep. One other thing that may play a role is vitamin D. In a study done in school children vitamin D supplementation reduced the cases of flu compared to placebo. So before getting the flu shot consider what might be a more effective way to prevent the flu.
References
http://www.cdc.gov/flu/about/disease/us_flu-related_deaths.htm Accessed Nov. 10th, 2014
Jefferson T, Di Pietrantonj C, Rivetti A, Bawazeer GA, Al-Ansary LA, Ferroni E. Vaccines for preventing influenza in healthy adults. Cochrane Database of Systematic Reviews 2010, Issue 7. Art. No.: CD001269.
Jefferson T, Di Pietrantonj C, Al-Ansary LA, Ferroni E, Thorning S, Thomas RE. Vaccines for preventing influenza in the elderly. Cochrane Database of Systematic Reviews 2010, Issue 2. Art. No.: CD004876.
Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 May;91(5):1255-60.
