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Ask a Librarian: Influenza

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According to Health Canada, Influenza and pneumonia are ranked among the top 10 leading causes of death in the country. It is estimated that influenza causes approximately 12,200 hospitalizations and 3,500 deaths nation-wide each year.

Influenza is a respiratory illness caused primarily by the influenza A and B viruses. While most people recover in 7 to 10 days, severe illness can occur.

Getting vaccinated each fall is the best way to help prevent influenza infection.

Here are some resources on Influenza selected by Joule’s Ask a Librarian team using a variety of tools included with CMA membership.


Clinical summary from DynaMed

Access DynaMed online or through the mobile app to get concise overviews and detailed recommendations, medical graphics and images, drug information from Micromedex and more.

Influenza in Children

Prevention and Screening


  • annual influenza vaccination recommended for all persons aged ≥ 6 months old without contraindications
  • optimal time for vaccination is before influenza activity begins in the community (offer before the end of October in Northern hemisphere when possible)
  • target groups with increased emphasis for providing routine vaccination
    • persons at risk for complications associated with severe influenza
      • children aged 6-59 months
      • adolescents who are or will be pregnant during the influenza season
      • children with chronic pulmonary (including asthma), cardiovascular (except isolated hypertension), renal, hepatic, neurological, hematologic, or metabolic disorders (including diabetes mellitus)
      • children with immunocompromise, including immunosuppression due to medications or HIV infection
      • children and adolescents (aged 6 months to 18 years) who are receiving aspirin- or salicylate-containing medications and who might be at risk for Reye syndrome after influenza virus infection
      • American Indians/Alaskan Natives
      • patients in long-term care facilities
      • children who are extremely obese (body mass index ≥ 40 kg/m2)
    • persons who live with or care for persons at higher risk for influenza-related complications
      • household contacts and caregivers of
        • children < 5 years old (especially contacts of children < 6 months old)
        • adults aged ≥ 50 years
        • persons with medical conditions that put them at higher risk for severe complications from influenza
  • inactivated influenza vaccine (IIV) and live, attenuated, cold-adapted virus (LAIV) recommended vaccine types for children during 2019-2020 influenza season
    • Centers for Disease Control and Prevention and American Academy of Pediatrics do not recommend 1 formulation over another
    • dosing for IIV
      • 0.5 mL dose intramuscularly for most vaccine formulations, with age indication varying by product
      • 0.25 mL dose intramuscularly for Afluria Quadrivalent in children aged 6-35 months (standard 0.5 mL dose for children aged ≥ 3 years)
      • 0.25 mL dose or 0.5 mL dose intramuscularly for Fluzone Quadrivalent in children aged 6-35 months (standard 0.5 mL dose for children aged ≥ 3 years)
    • dosing for LAIV 0.2 mL using prefilled single-use intranasal sprayer (0.1 mL per nostril) for patients aged 2-49 years
    • schedule
      • for children aged 6 months to 8 years
        • 2 doses given ≥ 4 weeks apart needed for children during their 1st season of vaccination to optimize immune response
        • children should only have 1 dose if they had ≥ 2 doses of trivalent or quadrivalent vaccination in prior seasons
        • children without ≥ 2 doses prior to July 1, 2019, should have 2 doses ≥ 4 weeks apart
      • give 1 dose for persons aged > 9 years
  • seasonal vaccine efficacy
    • live attenuated and inactivated influenza vaccines reduce incidence of influenza and influenza-like illness in healthy children > 2 years old
    • influenza vaccination associated with reduced risk of influenza-associated pneumonia
    • insufficient evidence to determine if influenza vaccination prevents exacerbations in asthmatic patients, but influenza vaccination with inactive vaccine does not cause exacerbations
  • influenza vaccination typically safe and well tolerated
    • most common adverse effects include injection site reactions, headache, fatigue, myalgia, fever, and malaise
    • possible very low risk of Guillain-Barre syndrome after influenza vaccination
    • egg allergy associated with low risk of adverse events, and not considered contraindication for influenza vaccination
      • if history of only hives following egg exposure, give any licensed or recommended influenza vaccine otherwise appropriate based on patient age and health status
      • for patients with a history of severe reaction to egg or egg proteins
        • give any licensed or recommended influenza vaccine otherwise appropriate based on patient age and health status
        • administer selected vaccine in inpatient or outpatient medical setting
        • administration should be supervised by health care provider able to recognize and manage severe allergic conditions
  • see Seasonal influenza vaccines in children for additional information


Recent update:

30 Sep 2019

CDC ACIP 2019-2020 recommendations on prevention and control of seasonal influenza with vaccines (MMWR Recomm Rep 2019 Aug 23)

Preview (CMA members can access all summaries via this link)


Clinical summary from Essential Evidence Plus

Essential Evidence Plus is an evidence-based point of care tool with access to over 13,000 topics, guidelines, abstracts and summaries. For a synopsis of new evidence reviewed by the Essential Evidence Plus editorial team, subscribe to the POEMs daily newsletter.


Overall Bottom Line

  • Yearly influenza vaccination is recommended by ACIP (US) for persons over the age of 6 months. (A level evidence)
  • 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 level evidence)
  • Rapid antigen tests are most useful during the beginning and end of the flu season. (C level evidence)
  • 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 level evidence)
  • Predictors of adverse outcome in the elderly include increased age, previous hospitalization, comorbidities, gender, and number of outpatient visits in the previous year. (A level evidence)

Read more via Essential Evidence Plus (CMA members only)


Synopsis of clinical studies in POEMs by Essential Evidence Plus:

POEM: H1N1 influenza vaccination during pregnancy not associated with problems in exposed offspring

Clinical question
Does flu immunization during pregnancy affect child health?

Bottom line
There was no association found between influenza vaccination of pregnant women with a monovalent (H1N1) vaccine and subsequent illness in the children exposed in utero, over the first 5 years of their lives.

Walsh LK, Donelle J, Dodds L, et al. Health outcomes of young children born to mothers who received 2009 pandemic H1N1 influenza vaccination during pregnancy: retrospective cohort study. BMJ 2019;366:l4151.


Further reading

Book Chapters via ClinicalKey (CMA members only):

ClinicalKey drives better care by delivering fast, concise answers, and deep access to evidence whenever, wherever you need it. ClinicalKey includes access to 1,000+ textbooks, 600 full-text journals, images, videos and customizable patient handouts across 30+ medical specialties


Articles via CMAJ:

Five things to know about …: High-dose influenza vaccination

Daniel Dalcin and Jeffrey C. Kwong, CMAJ  March 18, 2019  191  (11)  E313


Medicine and society: Kingston’s experience with Spanish influenza: explaining the highest death rate in Canada

Andrew Belyea, CMAJ  April 01, 2019  191  (13)  E367-E369


Clinical Practice Guidelines via CPG Infobase:

CPG Infobase contains approximately 1,200 evidence-based Canadian clinical practice guidelines (CPGs) developed or endorsed by authoritative medical or health organizations in Canada.

Vaccine recommendations for children and youth for the 2019/2020 influenza season, Canadian Paediatric Society, Published on: 2019-10

Canadian immunization guide chapter on influenza and statement on seasonal influenza vaccine for 2019-2020, National Advisory Committee on Immunization, Published on: 2019-05

Canadian Clinical practice guidelines on Influenza in the CPG Infobase.


Drug Information via CPS online and on the RxTx app (CMA members only):

CPS offers 2000+Canadian product monographs for drugs, vaccines and natural health products that are developed by manufacturers, approved by Health Canada and optimized by CPhA editors

Search “influenza” in the CPS on the RxTx app to find related drug monographs that provide information regarding dosage, adverse effects, drug interactions and clinical pharmacology, as well as the drug table “Drugs used for the Prevention and Treatment of Influenza”.

The CPS Online includes patient handouts. Search “influenza” and select “Information for patients” to access handouts on drugs for this indication.


Free information sources

Flu (influenza): For health professionals - Government of Canada – including FluWatch Surveillance

Influenza Resources  – Infection Prevention and Control Canada

Influenza – World Health Organization

Immunize Canada


Need more information or have a more focused clinical question on influenza (or any other clinical topic of interest)? Contact the Ask a Librarian team to request a literature search.


This material is for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice. The opinions stated by the authors are made in a personal capacity and do not necessarily reflect those of the Canadian Medical Association and its subsidiaries including Joule.  Feel passionate about physician-led innovation? Please connect with us at

About the author(s)

CMA Joule’s medical librarians are the professionals behind “Ask a Librarian”, a service for all CMA members looking for clinical search expertise. This experienced team of librarians can support you by searching on your behalf, teaching you effective search strategies or training you to use our clinical resources.