Influenza in Healthcare Settings

Question & Answers

Influenza and Influenza Vaccine Information for Healthcare Personnel

Revision: October 31, 2008

What is influenza (the flu)?

Influenza is a respiratory illness caused by the influenza virus. Symptoms of influenza infection may include sudden onset of fever (usually high), muscle aches, headache, extreme tiredness, cough, sore throat, and runny or stuffy nose.

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How serious is influenza?

Influenza infects an average of 5-20% of the U.S. population each year. On average, more than 200,000 people are hospitalized and 36,000 people die of influenza or its complications each year. Complications of influenza include pneumonia, bronchitis, sinus and ear infections, and worsening to approximately 5 days after symptoms start. Children may be able to spread influenza to others for 10 or more days after their illness onset.

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How is influenza spread?

Influenza spreads mainly from person to person. The virus is spread primarily by droplets that are generated by coughing and sneezing of infected persons. Transmission may also occur by touching a surface contaminated with influenza virus and then touching the eyes, nose, or mouth.

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When can a person spread influenza?

People develop symptoms 1-4 days after they are infected, with an average of 2 days. Adults may be able to spread influenza to others from 1 day before developing symptoms to approximately 5 days after symptoms start. Children may be able to spread influenza to others for 10 or more days after their illness onset.

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What can I do to prevent myself and my patients from getting influenza?

Get vaccinated! Influenza vaccination is the best way to reduce your chances of getting ill from influenza or giving influenza to your patients, your co-workers, and your family. There are two types of influenza vaccine: 1) trivalent inactivated influenza vaccine (TIV) (flu shot), and 2) live, attenuated influenza vaccine (LAIV) (nasal spray). The inactivated vaccine is approved for persons 6 months of age or older. LAIV is approved for healthy persons 2-49 years of age who are not pregnant and who do not have underlying medical conditions that indicate that they should receive TIV. For further information about influenza vaccine see http://www.cdc.gov/flu/.

Most healthcare workers can receive either LAIV or TIV. The inactivated influenza vaccine is preferred for health care personnel who work with patients with severely weakened immune systems (e.g., patients who have recently had a hematopoietic stem cell transplant and require a protected environment) because of a theoretical risk that LAIV could be transmitted to severely immunocompromised persons.

Healthcare personnel who are vaccinated with LAIV (nasal spray) should not care for patients with severely weakened immune systems for 7 days after vaccination. However, there have not been any reports of healthcare workers who were recently vaccinated with LAIV transmitting the vaccine viruses to vulnerable patients. In addition, influenza antiviral medications oseltamivir or zanamivir can be used for the treatment and prevention of influenza. For more information about influenza antiviral medications see http://www.cdc.gov/flu/professionals/antivirals/index.htm.

Another important way to prevent the spread of influenza is to follow infection control recommendations including hand hygiene, Respiratory Hygiene/Cough Etiquette, Standard Precautions, and Droplet Precautions.

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How well do the flu shot and nasal spray vaccines work?

The likelihood that influenza vaccine will protect a person depends on at least two things: 1) characteristics of the person being vaccinated (such as their age and health) and 2) the similarity or "match" between the influenza viruses in the vaccine and those spreading in the community. The closer the “match” between the influenza viruses in the vaccine and those spreading in the community, the more effective the vaccine is likely to be in preventing influenza. Influenza vaccine effectiveness (ability to prevent influenza) has been as high as 70-90% in healthy military and working populations, when the viruses in the vaccine were well matched to circulating flu viruses.

Effectiveness has been lower, sometimes substantially lower, when circulating viruses were sub-optimally matched with those in the vaccine. However, even during years when there is reduced vaccine effectiveness, vaccination can still offer protection against influenza. This is because antibodies created through vaccination with one strain of influenza can provide protection against different, but related strains of influenza (this is called cross-protection). While a less than ideal virus match can reduce the vaccine’s effectiveness it can still prevent many illnesses and can prevent flu-related complications.

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Why should healthcare personnel get vaccinated to prevent influenza?

All health care personnel should get vaccinated each year to protect themselves from getting influenza and to prevent transmission of influenza to their patients, coworkers, family members, and close contacts. Vaccination also can prevent persons at higher risk of complications from developing severe influenza-related illness or death.

Recent standards have been published requiring that health care organizations offer influenza vaccination to personnel including volunteers and licensed independent contractors with close patient contact free of charge Implementation of policies is recommended to encourage health care personnel vaccination (e.g., obtaining signed statements from personnel who decline influenza vaccination). Some states have enacted laws requiring influenza vaccination of health care personnel.

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What are the side effects of the flu shot (TIV)?

Mild arm soreness and redness or swelling at the injection site are the most common side effects and may last 1 to 2 days. Other potential side effects such as allergic reactions, fever, fatigue, and body aches are uncommon. One potential side effect that some people worry about is Guillain-Barré Syndrome (GBS), because GBS was seen in some people who received the swine flu vaccine in 1976. There are many causes of GBS, and each year there are an estimated 10–20 GBS cases per 1 million adults. None of the studies conducted using influenza vaccines other than the 1976 swine influenza vaccine have demonstrated a substantial increase in GBS associated with influenza vaccines. If GBS is a side effect of influenza vaccines other than 1976 swine influenza vaccine, the estimated risk for GBS (on the basis of the few studies that have demonstrated an association between vaccination and GBS) is low (i.e., approximately one additional case per 1 million persons vaccinated).

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What are the side effects of the nasal spray vaccine (LAIV)?

The viruses in the nasal spray vaccine are attenuated (weakened) and do not cause influenza. In children, side effects from LAIV can include runny nose, headache, vomiting, muscle aches, and fever. In adults, side effects from LAIV can include runny nose, headache, sore throat, and cough. Fever is not a common side effect in adults receiving the nasal spray influenza vaccine.

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Who should get influenza vaccine?

The Advisory Committee on Immunization Practices recommends that persons who want to reduce the risk of becoming ill with influenza or transmitting influenza to others and those who live with, may have close contact with, or care for persons at high risk for influenza-related complications and children <6 months of age should be vaccinated with either TIV or LAIV including:

  • Healthy children ≥2 years of age:
  • Healthy adults ≤50;
  • Healthy health care personnel;
  • Healthy household contacts (including children older than 6 months) and caregivers of children aged < months (i.e., aged <5 years)
  • Healthy household contacts (including children) and caregivers of persons with medical conditions that put them at higher risk for severe complications from influenza listed below.

ACIP also recommends influenza vaccination only with TIV (flu shot) for persons who are at increased risk for complications from influenza and their contacts. These persons should continue to be a focus of vaccination efforts. Persons at increased risk who should be vaccinated with TIV (flu shot) include:

  • All children aged 6months until their 5th birthday ;
  • All persons aged ≥50 years;
  • Children and adolescents (aged 6 months–18 years) who are receiving long-term aspirin therapy and who therefore might be at risk for experiencing Reye syndrome after influenza virus infection;
  • Women who will be pregnant during the influenza season;
  • Adults and children who have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal or hepatic dysfunction, hepatic, hematological or metabolic disorders (including diabetes mellitus);
  • Adults and children who have immunosuppression (including immunosuppression caused by medications or by HIV);
  • Adults and children who have any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration;
  • Residents of nursing homes and other chronic-care facilities.

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Who should not get the flu shot?

  • People who have a severe allergy to chicken eggs,
  • People who have had a severe reaction to an influenza vaccination,
  • People who have developed Guillain-Barré syndrome within 6 weeks of getting an influenza vaccine,
  • Children less than 6 months of age (influenza vaccine is not approved for this age group), and
  • People who have a moderate to severe illness with a fever (they should wait until they recover to get vaccinated).

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Who can get vaccinated with LAIV (nasal spray) rather that the flu shot?

The following populations can get either the LAIV (nasal spray) or the flu shot:

  • Healthy person 2-49 years of age who are not pregnant
  • Health care personnel who care for patients with severely weakened immune systems (e.g., patients who have recently had a hematopoietic stem cell transplant and require a protective environment) can receive LAIV, however they should refrain from contact with severely immunosuppressed patients for 7 days after vaccine receipt but The Advisory Committee on Immunization Practices should not be restricted from caring for less severely immunocompromised patients.

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Should pregnant women or women who are breastfeeding be given the flu shot?

Yes, women who are or will be pregnant during the influenza season should be vaccinated with the flu shot; however, pregnant women should not receive live attenuated influenza vaccine (nasal spray). The flu shot and nasal spray are safe for mothers who are breastfeeding and will not harm their infants.

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Who should talk with their physician before getting the flu vaccine or delay getting the vaccine?

  • Persons with allergies to eggs or thimerosal or a prior allergic reaction to the flu vaccination.
  • Persons with a history of Guillain-Barré syndrome.
  • Persons with moderate-to-severe acute febrile illness usually should not be vaccinated until their symptoms have abated. However, minor illnesses with or without fever do not contraindicate use of influenza vaccine, particularly among children with mild upper-respiratory tract infection or allergic rhinitis.

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Can influenza vaccines cause influenza?

No, neither type of vaccine causes influenza. The flu shot contains killed or inactivated influenza viruses and LAIV contains influenza viruses that have been attenuated (weakened) so they do not cause disease; however, minor symptoms can occur with either vaccine.

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How can I tell if I or one of my patients has influenza?

Because the symptoms of influenza are similar to those caused by other respiratory viruses, laboratory testing is needed to confirm the diagnosis of influenza. Check with your hospital's laboratory or infection control personnel to find out what tests are available at your facility. Information about laboratory testing can be found at http://www.cdc.gov/flu/professionals/diagnosis/labprocedures.htm.

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What should I do if I suspect influenza in a patient seen in my facility?

First, notify the patient's physician and your facility’s infection control personnel. Infection control personnel can recommend steps including Respiratory Hygiene/Cough Etiquette and Standard and Droplet Precautions to limit the spread of influenza to other patients and staff, and they can look for and isolate additional cases of influenza in the facility. All patients who have acute onset of fever and cough (http://www.cdc.gov/flu/keyfacts.htm) during influenza season should be evaluated for influenza. Patients in long-term care facilities with flu-like illness should be tested for influenza when they have fever or respiratory symptoms during influenza season, especially if no other diagnosis is apparent (http://www.cdc.gov/flu/professionals/infectioncontrol/longtermcare.htm).

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What should I do if I develop influenza symptoms?

Seek medical attention and report your illness to your supervisor and to the occupational health clinic or infection control department/personnel at your facility. You can avoid spreading influenza to others by staying at home when you are ill, covering your mouth with a tissue when coughing or sneezing, and performing hand hygiene after contact with your respiratory secretions.

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Is there a treatment for influenza?

Yes. The influenza antiviral medications zanamivir and oseltamivir are effective against influenza types A and B. To reduce the number of days of influenza illness and lessen symptom severity, these medications should be started within the first 2 days after symptoms begin. They can also be used to prevent influenza. Amantadine and rimantadine are not recommended for use in the United States because of high levels of resistance among influenza A viruses. http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm

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Is there any medication to prevent disease if I am exposed to influenza?

Yes. Either oseltamivir or zanamivir can be used to prevent influenza A and B. However, zanamivir is not recommended for treatment for patients with underlying airway disease. http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm

For more information about influenza or influenza vaccine, call 1-888-232-6348 or visit the CDC Web site at: www.cdc.gov/flu

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Date last modified: Nov 6, 2008
Content source: 
Division of Healthcare Quality Promotion (DHQP)
National Center for Preparedness, Detection, and Control of Infectious Diseases