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October 30, 2015

Increasing EMS provider influenza vaccination will decrease transmission

It is a good bet that almost every EMS professional has suffered from influenza at one point. The Center for Disease Control and Prevention (CDC) estimates the 2013-2014 flu season resulted in more than 35 million flu-related illnesses and about 400,000 flu-related hospitalizations [1]. In this country, almost half of all influenza-related hospitalizations and more than 90 percent of all influenza-related deaths occur in individuals 65 years of age or older [2].

What is influenza?

Influenza is a highly contagious viral infection that affects an individual's nose throat, and lungs. There are three genera of the viral family orthomyxoviridae; however only two (influenza A and influenza B) are responsible for most cases of the influenza in humans. There can be a number of variants of these two different viral types. The separate variants are called serotypes and classification is based on the types of protein antigens present on the surface of the viral organism. When antigenically similar to circulating strains, the influenza vaccine can prevent between 70 percent and 90 percent of influenza cases [3, 4].

Why are there so many strains of the flu?

Repeated viral replication over time can result in two significant changes to the viruses. In a process called antigenic drift, tiny changes in the viral genes can produce two viruses that are very similar to one another, but not quite the same.

Over time, these seemingly insignificant differences can accumulate resulting in viral changes significant enough that the human immune system human no longer recognizes the new virus. When this happens patients once immune to the original virus will not be immune to the new virus.

The second type of change is called antigenic shift, which results when two or more different viruses combine producing a new strain with a combination of surface antigens found on the original virus. This can result is almost immediately loss of immunity for an individual. The 2009 H1N1 outbreak was the result of antigenic shift between human, avian, and porcine viruses [5].

How effective are flu vaccines?

In order to determine what viruses are included into any year's flu vaccination, experts from around the world analyze what viral strains are circulating the globe and how well the most current vaccine is protecting the population. If the experts find a new strain of virus, they will test a group of people who received the previous year's vaccine to see if those individuals are producing antibodies for the new strain. If they are not or the antibodies levels are low, the experts will recommend updating the flu vaccine to protect against the new strain [6].

During the 2014-2015 flu season, the CDC [7] estimates the vaccine was 23 percent effective in preventing outpatient medical visits due to laboratory-confirmed influenza, after adjusting for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment. Most of the infections were due to influenza A viruses [8].

Although the CDC acknowledges the relatively low effectiveness of the vaccine during the season, more than two-thirds of the influenza A viruses antigenically drifted from previous years [9]. The 2015-2016 vaccine will account for the antigenic drift [10]. An interim analysis conducted between May 24–September 5, 2015 found that all of the subtypes of influenza A and B viruses found were antigenically similar to viruses found in the previous year [11].

BoundTree UniversityWhy should EMS providers receive flu shots?

In-hospital evidence suggests that improving immunization rates among health care workers helps to both improve morbidity and mortality among patients and decrease absenteeism [12-14]. Unvaccinated EMS personnel may represent a significant risk of influenza infection for patients and family members [15]. A survey conducted in upstate New York found the rate of vaccination against influenza was significantly lower for EMS personnel (21 percent) compared to emergency department personnel (65 percent) serving the same community [15]. This is despite the fact that 71 percent of the EMS personnel believed the very nature of emergency work exposes the provider to potential influenza infection and 62 percent were concerned about becoming infected at work and transmitted the virus to their own family members.

A convenience sample of EMS personnel from 14 North Carolina EMS systems found that almost every one of the 601 EMTs and paramedics who responded reported having worked a shift while suffering from influenza [16]. Of those who had not been vaccinated, one in four reported not being worried about getting influenza, one in five did not receive the vaccination because it was not required by their employer, and one in five did not think the vaccine was effective.

Vaccination against influenza is one of the most effective methods for preventing the spread of influenza [17]. Despite the concerns that EMS personnel about becoming infected and transmitting the virus to their own families, most choose not to get vaccinated.

In order to increase vaccination compliance, EMS agencies should implement a mandatory vaccination policy, provide the vaccination free of charge while the crews are on duty and promote an education campaign to address any fears EMS personnel have about the side effects of vaccination.


1. Centers for Disease Control and Prevention. (2014). New CDC reports shows benefits of flu vaccine last season but fewer than half of Americans say they have been vaccinated this season. Retrieved from

2.Thompson, M. G., Shay, D. K., Zhou, H., Bridges, C. B., Cheng, P. Y., Burns, E., Bresee, J. S., & Cox, N. J. (2010). Estimates of deaths associated with seasonal influenza - United States, 1976--2007. Morbidity and Mortality Weekly Report, 59(33), 1057-1062.

3.Bridges, C. B., Thompson, W. W., Meltzer, M. I., Reeve, G. R., Talamonti, W. J., Cox, N. J., Lilac, H. A., Hall, H., Klimov, A., & Fukuda, K. (2000). Effectiveness and cost-benefit of influenza vaccination of healthy working adults: A randomized controlled trial. Journal of American Medical Association, 284(13), 1655-1663. doi:10.1001/jama.284.13.1655

4.Demicheli, V., Jefferson, T., Rivetti, D., & Deeks, J. (2000). Prevention and early treatment of influenza in healthy adults. Vaccine, 18(11-12), 957-1030. doi:10.1016/S0264-410X(99)00332-1

5.Smith, G. J. D., Vijaykrishna, D., Bahl, J., Lycett, S. J., Worobey, M., Pybus, O. G., Ma, S. K., Cheung, C. L., Raghwani, J., Bhatt, S., Peiris, J. S. M., Guan, Y., Rambaut, A. (2009). Origins and evolutionary genomics of the 2009 swine-origin H1N1 influenza A epidemic. Nature, 459(7250), 1122–1125. doi:10.1038/nature08182

Grush, L. (2013). How health officials determine the viruses used in the flu vaccine. Retrieved from

7.Centers for Disease Control and Prevention. (2015). Seasonal influenza vaccine effectiveness, 2005-2015. Retrieved from

8.Flannery, B., Clippard, J., Zimmerman, R. K., Norwalk, M. P., Jackson, M. L., Jackson, L. A., Monto, A. S., Petrie, J. G., McLean, H. Q., Belongia, E. A., Gaglani, M., Berman, L., Foust, A., Sessions, W., Thaker, S. N., Spencer, S., & Fry, A. M. (2015). Early estimates of seasonal influenza vaccine effectiveness – United States. Morbidity and Mortality Weekly Reports, 64(1), 10-15. doi:10.15585/mmwr.mm6436a4.

9.Centers for Disease Control and Prevention. (2015). Fluview. 2014–2015 influenza season week 53 ending January 3, 2015. Retrieved from

10.Grohskopf, L. A., Sokolow, L. Z., Olsen, S. J., Bresee, J. S., Broder, K. R., & Karron, R. A. (2015). Prevention and control of influenza with vaccines: Recommendations of the advisory committee on immunization practices, United States, 2015–16 influenza season. Morbidity and Mortality Weekly Reports, 64(30), 818-825.

11.Blanton, L., Kniss, K., Smith, S., Mustaquim, D., Steffens, C., Flannery, B., Fry, A. M., Bresee, J., Wallis, T., Garten, R., Xu, X., Elal, A. I., Gubareva, L., Wentworth, D. E., Burns, E., Katz, J., Jernigan, D., & Brammer, L. (2015). Update: Influenza activity - United States and worldwide, May 24-September 5, 2015. Morbidity and Mortality Weekly Reports, 64(36), 1011-1016. doi:10.15585/mmwr.mm6436a4

12.Carman, W. F., Elder, A. G., Wallace, L. A., McAulay, K., Walker, A., Murray, G. D., et al. (2000). Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: A randomised controlled trial. Lancet, 355(9198), 93-97. doi:10.1016/S0140-6736(99)05190-9

13.Potter, J., Stott, D. J., Roberts, M. A., Elder, A. G., O'Donnell, B., Knight, P. V., & Carman, W. F. (1997). Influenza vaccination of health care workers in long-term-care hospitals reduces the mortality of elderly patients. Journal of Infectious Disease, 175(1), 1-6. doi:10.1093/infdis/175.1.1

14.Salgado, C. D., Farr, B. M., Hall, K. K., & Hayden, F. G. (2002). Influenza in the acute hospital setting. Lancet Infectious Diseases, 2(3), 145-155. doi:10.1016/S1473-3099(02)00221-9

15.Rueckmann, E., Shah, M. N., & Humiston, S. G. (2009). Influenza vaccination among emergency medical services and emergency department personnel. Prehospital Emergency Care, 13(1), 1-5. doi:10.1080/10903120802471949

16.Hubble, M. W., Zontek, T. L., & Richards, M. E. (2011). Predictors of influenza vaccination among emergency medical services personnel. Prehospital Emergency Care, 15(2), 175-183. doi:10.3109/10903127.2010.541982

17.Rebmann, T., Wright, K. S., Anthony, J., Knaup, R. C., & Peters, E. B. (2012). Seasonal and H1N1 influenza vaccine compliance and intent to be vaccinated among emergency medical services personnel. American Journal of Infection Control, 40(7), 632-636. doi:10.1016/j.ajic.2011.12.016

About the Author

Kenny Navarro is an Assistant Professor in the Department of Emergency Medicine at the University of Texas Southwestern Medical School at Dallas. He also serves as the AHA Training Center Coordinator for Tarrant County College. Mr. Navarro serves as an Emergency Cardiovascular Care Content Consultant for the American Heart Association, served on two education subcommittees for NIH-funded research projects, as the Coordinator for the National EMS Education Standards Project, and as an expert writer for the National EMS Education Standards Implementation Team. Send correspondence concerning any articles in this section to Kenneth W. Navarro, The University of Texas Southwestern Medical School at Dallas, 5323 Harry Hines Blvd MC 8890, Dallas, Texas 75390-8890, or e-mail