The Center for Disease Control (CDC) recommends a yearly flu vaccine for everyone 6 months of age or older. They estimate that between 5% and 20% of the United States population gets the flu each year, which can lead to days missed from work or school and have a meaningful financial impact. The flu may also result in more than 200,000 hospitalizations in our country each year.1 Influenza can lead to death, which is one of the main reasons that public health campaigns encourage vaccination.
But the decision to vaccinate against the flu is not straightforward. When we are making a choice to vaccinate ourselves or our children, we need to first answer four questions:
- What is the severity of this disease?
- How effective is vaccination?
- What are the risks of vaccination?
- Are there ethical reasons to accept or decline vaccination?a
This article addresses each of these questions so that you can make a thoughtful and informed choice.
Severity of Influenza Disease
There is no way to precisely know the number of deaths that are caused by seasonal influenza each year. The CDC estimates that from 1976 to 2006, deaths due to the flu ranged from 3,000 to 49,000 per year.2 But these numbers are a result of statistical methods that estimate a link between influenza, pneumonia, respiratory, and circulatory disorders. Mortality statistics commonly do not distinguish between "influenza and pneumonia" as the cause of death. This can result in numbers that do not accurately reflect the impact of influenza itself. In fact, the most recent CDC data reports only 500 deaths directly due to influenza in 2010.3
Studies repeatedly show that on years when influenza A (H3N2) viruses predominate, the death rates are more than double that of years when influenza A (H1N1) or influenza B predominate.2 Studies also confirm that 90% of influenza associated deaths occur among adults 65 years and older.2
While influenza certainly can lead to death, the likelihood that this will happen is probably much less than some statistics and media reports would lead us to believe.
The influenza virus is always evolving. Nobody can predict exactly what strain will emerge this year or how virulent it will be. This makes it challenging for experts to create an effective vaccine. The World Health Organization is responsible for choosing the three or four strains of the virus that are most likely to cause illness each winter. These are the ones included in the flu vaccine. For years, the flu vaccine has been "trivalent," which means that it includes 3 different strains: two type A strains (H1N1 and H3N2) and one type B strain. A "quadrivalent" vaccine that includes an additional type B strain is available for the first time this 2013-2014 season.
The flu vaccine is most effective when it contains virus strains that match those circulating in the population. But the efficacy of the flu vaccine also depends heavily on who is vaccinated. A CDC report concluded that the flu vaccine for the 2012-2013 season was 56% effective in the population overall.4 For the elderly, however, it was only 27% effective. For influenza A (H3N2), which is the most likely to cause serious disease, the effectiveness of the flu vaccine was 47% overall. And what is most striking is that the protection against this virulent strain in the elderly was only 9%. Unfortunately, those who are most likely to suffer serious consequences of the flu are least likely to gain protection from vaccination. A new high-dose flu vaccine is offered to seniors this year in an attempt to improve these statistics.5
The flu shot commonly causes mild side effects such as swelling at the injection site, fever, headache, nausea, or muscle aches. The nasal spray may also cause runny nose, sneezing, wheezing, or cough. The CDC recommends monitoring for serious but rare side effects such as allergic reactions, high fever, behavior changes, and Guillain-Barre Syndrome (paralysis).6
There are other potential risks of flu vaccination that I encourage you to consider. By the age of 6, children following the recommended immunization schedule will have received 28 injections for 13 diseases. These numbers do not include the annual flu shot. Depending on risk factors and past vaccination status, adults may also receive multiple vaccinations. While each of these vaccinations has been studied individually, there are no long-term studies on the effect of cumulative exposure to multiple vaccines over the course of a person's lifetime.
Vaccines contain not only the proteins (antigens) needed to stimulate immunity, but also a formidable list of additives (called excipients). There are several different forms of the flu vaccineb available, so I will not include a comprehensive list of additives here. Some flu shots include thimerosol (mercury), which is a known neurotoxin. Some contain formaldehyde, which is classified as a carcinogen. Some contain antibiotics such as neomycin and polymyxin B. Most are grown in egg protein, which can trigger allergic reactions.
While proponents of immunization claim that the quantity of additives in vaccines is too small to cause health problems, the fact is that we do not know. We do not have data on the cumulative exposure of injected toxins. And we do not have data on the synergistic effect of multiple toxins at once. With a recommendation for annual flu vaccination beginning at 6 months of age, a baby born today could receive 70 to 100 flu vaccines over the course of a lifetime. Compared to following the immunization schedule without flu vaccination, this more than doubles their lifetime vaccine burden.
I would be remiss in discussing the risks of flu vaccination without a discussion of its effect on the immune system. The human body's response to the influenza virus is complex. It does not only involve antibody production to viral proteins (the current goal of vaccination), but also CD8+ T cells, alveolar macrophages, and other lung phagocytes.7 Vaccine-induced immunity is specific to a limited number of virus strains and declines rapidly over time.8 While natural infection does not offer lifetime protection against another flu infection either, recent studies suggest that there is meaningful benefit to natural influenza immunity. A 2011 study showed that vaccinated children failed to produce the age-dependent increase in virus-specific CD8+ T cell response that was seen in unvaccinated children.9 This CD8+ T cell response is important protection against future seasonal or pandemic influenza viruses. While the long-term consequences are yet to be seen, we have to consider immune compromise a viable risk of annual flu vaccination.
An Ethical Choice
The final question we need to answer is whether there are ethical reasons to vaccinate or not vaccinate against influenza.
Healthcare workers or others who are around chronically ill or elderly might consider vaccination in order to prevent transmission to these vulnerable populations. It can also be argued that the elderly should be vaccinated because of the potential severity of the disease at this age. While I can certainly respect these arguments, I would find them more convincing if the flu shot had greater efficacy. Remember that the flu vaccine is less than 50% effective overall against the most severe strain of the virus (H3N2) and its efficacy in the elderly against this strain is almost zero. But even partial protection may be enough reason for some to feel ethically obligated to choose vaccination.
On the other side of the aisle, there is the argument that vaccination against the flu may lead to more rapid mutations and virulent strains of the virus. This concern is supported by recent studies in mice that show malaria vaccination can contribute to more virulent malaria parasites.10 This phenomenon has been seen with the Pneumococcal vaccine, where strains that used to be rare have emerged as common and can be resistant to antibiotics.11 Experts have concern that this will also happen with the HPV vaccine.11 Any time it is impossible to vaccinate against all strains of a pathogen, there is concern that vaccination may allow non-targeted strains to become more common and virulent. For some, this provides ethical justification to refuse vaccination.
To Vaccinate or Not
Let's return to the four questions we must answer before choosing to vaccinate.
What is the severity of the flu? While it does have the potential to be deadly, in the majority of the population, the risk is small.
What is the effectiveness of the flu vaccine? Last year, it was 56% effective in the overall population (47% against H3N2) and 27% effective in the elderly (9% against H3N2).
What are the risks of vaccination? Besides mild and common side effects, the vaccine may cause some rare but serious effects including paralysis. It likely leads to the overall toxic body burden and may compromise long-term immunity against new or pandemic strains.
Are there ethical reasons compelling enough to accept or decline vaccination? That is for you to decide.
1. Thompson WW, Shay DK, Weintraub E et al. Influenza-associated hospitalizations in the United States. JAMA. 2004;292 (11):1333-1340.
2. Estimates of Death Associated with Seasonal Influenza - United States 1976 - 2007. Morbidity and Mortality Weekly Report. 2010. Accessed on 10/8/13.
3. FastStats Influenza. 2010. Accessed on 10/8/13.
4. Interim Adjuted Estimates of Seasonal Influenza Vaccine Effectiveness - United States February 2013. Morbidity and Mortality Weekly Report. 2013. Accessed on 10/8/13.
5. What You Should Know for the 2013-2014 Influenza Season. 2013. Accessed on 10/8/13.
6. 2013-2014 Seasonal Influenza Vaccine Safety. 2013. Accessed on 10/8/13.
7. Laidlaw BJ, Decman V, Ali MA et al. Cooperativity between CD8+ T cells, non-neutralizing antibodies, and alveolar macrophages is important for heterosubtypic influenza virus immunity. PLoS Pathog. 2013;9 (3):e1003207.
8. Prevention and Control of Influenza with Vaccines. Morbidity and Mortality Weekly Report. 2010. Accessed on 10/8/13.
9. Bodewes R, Fraaij PL, Geelhoed-Mieras MM et al. Annual vaccination against influenza virus hampers development of virus-specific CD8(+) T cell immunity in children. J Virol. 2011;85 (22):11995-12000.
10. Barclay VC, Sim D, Chan BH et al. The evolutionary consequences of blood-stage vaccination on the rodent malaria Plasmodium chabaudi. PLoS Biol. 2012;10 (7):e1001368.
11. Sears, RW. The Vaccine Book. New York, NY: Little, Brown and Company; 2007.
a In the end, the decision to vaccinate is a personal choice based on your own health situation and belief system. This article is in no way intended to be medical advice. It is always recommended to consult with your doctor before making any decision for or against vaccination.
b There are several flu vaccines available. The trivalent vaccine is available as a standard shot grown in eggs (ages 6 months and up), a shot grown in cell culture (ages 18 and up), an egg-free shot (ages 18-49), a high-dose shot (ages 65 and up), or an intradermal shot (ages 18-64). The quadrivalent vaccine is available as a standard shot (ages 6 months and up) or a nasal spray (for healthy people ages 2-49). 5