Can Influenza Cause Injury and/or Death?
The influenza virus is constantly mutating and this frequent change makes it difficult to know exactly which type A and B strains will be circulating during the upcoming flu season.1 2 One particular strain of influenza may be predominant early in a flu season, while another different strain may emerge later in the season. Timing, severity and duration of the flu season varies widely from year to year, depending on the prevalent circulating influenza strains that are associated with either mild, moderate or severe illness.3
Official estimates of annual influenza-associated deaths in the United States have varied widely during the last half century.4 5 In the past, the CDC has estimated between 3,000 and 49,000 influenza-related deaths occur every year in the U.S., but the actual number is unknown because influenza-related deaths for persons over age 18 are not required to be reported to the CDC.6 7 8
A 2005 article published in the British Medical Journal asked the question: "Are U.S. Flu Death Figures More PR Than Science?"9 The author analyzed the U.S. Vital Statistics Mortality Data, which has been recorded for more than a century by the National Center for Health Statistics, and noted that from 1900 to 2010 the mortality rates for influenza deaths have been dropping and do not closely align with CDC influenza-related mortality estimates.10 Counting death certificates listing influenza as the cause of death could provide more accurate data. However CDC officials maintain this to be “a gross underestimation of seasonal influenza’s true impact.” 11 12
The impact of influenza-related illness on people also varies widely. A 2014 study published in The Lancet found that three-quarters of people confirmed with seasonal and pandemic influenza were asymptomatic, meaning they showed no symptoms of illness at all.13 14 People who do not show symptoms of influenza Illness, whether they have been vaccinated or not, can still transmit infection to others.15
However, for some people who get influenza, serious complications develop and can be life-threatening. These complications may include bacterial pneumonia, ear infections, sinus infections, dehydration, sepsis, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.16
IMPORTANT NOTE:NVIC encourages you to become fully informed about Influenza and the Influenza vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.
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1 CDC. Selecting Viruses for the Seasonal Influenza Vaccine May 4, 2016.
2 CDC. How the Flu Virus Can Change: “Drift” and “Shift” Sept. 27, 2017.
3 CDC. Summary of the 2015-2016 Influenza Season Sept. 29, 2016
4 CDC. Estimates of Deaths Associated with Seasonal Influenza --- United States, 1976—2007. MMWR Aug. 27, 2010; 59(33);1057-1062.
5 Fisher BL. Influenza Deaths: The Hype vs. The Evidence. National Vaccine Information Center Oct. 3, 2012.
6 Thompson, MG, Shay DK et al. Estimates of Deaths Associated with Seasonal Influenza --- United States, 1976--2007. MMWR Aug. 27, 2010; 59(33);1057-1062.
7 CDC. Influenza. Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015
8 CDC. Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu. Dec. 9, 2016.
9 Doshi P. Are U.S. Flu Death Figures More PR Than Science? BMJ 2005; 331 (7529): 1412.
10 NVIC. Influenza & Pneumonia Reported Deaths in U.S. 1940-2010 (Chart).
11 CDC. Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu. May 26, 2016.
12 Neel, J How Many People Die From Flu Each Year? Depends How You Slice The Data. NPR Aug. 26, 2010.
13 Johnson A, Zambon M. Comparative community burden and severity of seasonal and pandemic influenza: results of the Flu Watch cohort study. The Lancet 2014; 445–454.
14 The Lancet. Three-quarters of people with seasonal and pandemic flu have no symptoms. AAAS Mar. 16, 2014.
15 Magalhaes I, Eriksson M, Linde C et al. Difference in immune response in vaccinated and unvaccinated Swedish individuals after the 2009 influenza pandemic. BMC Infectious Diseases 2014; 14: 319.
16 CDC. Influenza – Flu symptoms & Complications. Oct. 20, 2017.