Essential Evidence

Last Updated on 2022-06-24 © 2022 John Wiley & Sons, Inc.

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Mark H. Ebell, MD, MS, Professor, College of Public Health, University of Georgia

Randall Forsch, MD, MPH, Assistant Professor, University of Michigan
Mark H. Ebell, MD, MS, Professor, College of Public Health, University of Georgia
Kenny Lin, MD, MPH, Professor of Family Medicine, Georgetown University

Overall Bottom Line

  • Yearly influenza vaccination is recommended by ACIP (US) for persons over the age of 6 months. A
  • Patients classically present with rapid onset of fever, cough, chills or rigors, sore throat, and myalgias. A clinical decision rule can be used to identify patients at low, moderate or high risk of influenza. B
  • Rapid antigen tests are most useful during the beginning and end of the flu season. C
  • Treatment is largely supportive; antiviral medications are recommended only if the likelihood of influenza is high and the patient presents within 24 hours of symptom onset. There is no evidence that they reduce serious complications or hospitalization. A
  • Predictors of adverse outcome in the elderly include increased age, previous hospitalization, comorbidities, gender, and number of outpatient visits in the previous year (Table 1). A


Table 1: Model to Predict Probability of Hospitalization With Pneumonia or Influenza or Death From Any Cause During Flu Season.

Symptom Score
70-74 years 14
75-79 years 28
80-89 years 42
>89 years 56
Male 9
Outpatient visits during the previous year  
1-6 11
7-12 22
>12 33
Previous hospitalization for pneumonia or influenza 63
Pulmonary disease 18
Heart disease 6
Renal disease or transplant 12
Dementia or stroke 22
Cancer 48
Score Probability*
<40 0.3%
40 to <60 1.2%
60 to <100 3.0%
≥100 15.4%
*Hospitalization for pneumonia or influenza, or all-cause mortality during flu season. From Hak E, Wei F, Nordin J, Mullooly J, Poblete S, Nichol KL. Development and validation of a clinical prediction rule for hospitalization due to pneumonia or influenza or death during influenza epidemics among community-dwelling elderly persons. J Infect Dis 2004;189:50-58. 10