Merck Manual

Please confirm that you are a health care professional

Loading

Influenza Vaccine

By

Margot L. Savoy

, MD, MPH, Lewis Katz School of Medicine at Temple University

Last full review/revision Jul 2019| Content last modified Jul 2019
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version

Based on recommendations by the World Health Organization and the US Centers for Disease Control and Prevention (CDC), vaccines for influenza are modified annually to include the most prevalent strains (usually 2 strains of influenza A and 1 or 2 strains of influenza B). Sometimes slightly different vaccines are used in the northern and southern hemispheres.

Preparations

There are 2 basic types of influenza vaccine:

  • Inactivated influenza vaccine (IIV)

  • Live-attenuated influenza vaccine (LAIV)

Trivalent vaccines are gradually being superseded by quadrivalent vaccines that cover an additional B virus strain. A trivalent recombinant influenza vaccine (RIV3) and a cell culture–based vaccine (ccIIV3) that do not contain egg protein are available. A high-dose trivalent vaccine is available for patients ≥ 65 years. (See also CDC: Different Types of Flu Vaccines.)

Indications

Annual vaccination against influenza is recommended for

  • All people ≥ 6 months

Inactivated influenza vaccine (IIV) can be given to all people ≥ 6 months, including pregnant women.

An age-appropriate formulation should be used.

Adults ≥ 65 years should be given high-dose IIV. The high dose is recommended only for those ≥ 65 years.

Recombinant influenza vaccine (RIV3) can be used in people aged 18 to 49 years.

Live-attenuated influenza vaccine (LAIV) can be given to healthy people aged 2 to 49 years who are not pregnant and who do not have immunocompromising conditions during the 2018–2019 flu season. Safety of LAIV has not been established in people with disorders that predispose them to complications from influenza, including advanced lung disease or asthma.

Health care workers who care for immunocompromised people (ie, those who require care in a protected environment) should be given IIV or RIV3 rather than LAIV (or they should avoid contact with the immunocompromised people for 7 days after getting the vaccine).

Contraindications and Precautions

The main contraindication for IIV is

  • A severe allergic reaction (eg, anaphylaxis) after previous dose of IIV

Precautions with IIV include

  • Moderate or severe acute illness with or without fever (vaccination is postponed until illness resolves)

  • Guillain-Barré syndrome (GBS) within 6 weeks after a previous dose of an influenza vaccine

Contraindications for LAIV include

  • A severe allergic reaction (eg, anaphylaxis) to a previous dose of LAIV

  • Immunocompromise (eg, due to disorders, including HIV infection, or use of immunosuppressants)

  • For children and adolescents, concomitant use of aspirin or other salicylates

  • Close contact with and/or caring for severely immunocompromised patients who require a protected environment (unless contact is avoided for 7 days after receiving LAIV)

  • Pregnancy

  • Anatomical or functional asplenia

  • Receipt of influenza antiviral drugs in the past 48 hours

  • Cerebrospinal fluid leak or a cochlear implant

  • Age < 2 years or ≥ 50 years

  • Age 2 to 4 years if children have asthma or have had wheezing or asthma episodes in the past 12 months

Precautions for LAIV include

  • Certain chronic disorders such as chronic lung, heart, kidney, liver, hematologic (eg, hemoglobinopathies), or metabolic (eg, diabetes mellitus) disorders

  • Asthma in people aged ≥ 5 years

  • Moderate or severe acute illness with or without fever (vaccination is postponed until illness resolves)

  • Guillain-Barré syndrome within 6 weeks after a previous dose of an influenza vaccine

  • Use of specific antiviral drugs: ie, amantadine, rimantadine, zanamivir, oseltamivir (these drugs are stopped 48 hours before vaccination and are not resumed for 14 days after vaccination)

The main contraindication for RIV3 is

  • A severe allergic reaction (eg, anaphylaxis) after a previous dose of RIV3

Precautions with RIV3 include

  • Moderate or severe acute illness with or without fever (vaccination is postponed until illness resolves)

  • Guillain-Barré syndrome within 6 weeks after a previous dose of an influenza vaccine

Precautions for patients with suspected egg allergy: Patients with a history of egg allergy who have experienced only hives after exposure to egg should be given the influenza vaccine. Any influenza vaccine that is otherwise recommended based on the recipient’s age and health status can be used.

Patients who report reactions to egg involving symptoms other than hives (such as angioedema, respiratory distress, light-headedness, or recurrent emesis) or who required epinephrine or another emergency medical intervention may similarly be given any influenza vaccine that is otherwise recommended based on the recipient’s age and health status. The vaccine should be given in an inpatient or outpatient medical setting and supervised by a health care practitioner capable of recognizing and managing severe allergic conditions.

Dose and Administration

The influenza vaccine is given yearly.

For IIV, the dose is

  • 0.25 mL IM for children aged 6 to 35 months

  • 0.5 mL IM for people ≥ 3 years

  • 0.1 mL for people aged 18 to 64 years, given intradermally

The smaller, intradermal dose can be used to conserve vaccine in times of shortage.

For LAIV, the dose is 0.1 mL, sprayed into each nostril (total dose is 0.2 mL).

For RIV3, the dose is 0.5 mL, given IM.

Adverse Effects

For IIV, adverse effects are usually limited to mild pain at the injection site. Fever, myalgia, and other systemic effects are relatively uncommon; however, people who have been vaccinated may mistakenly think that the vaccine is causing influenza. Such reactions do not contraindicate future vaccination, which should be encouraged.

Multidose vials contain thimerosal, a mercury-based preservative. Public concerns about a possible link between thimerosal and autism have proved unfounded; however single-dose vials, which are thimerosal-free, are available.

For LAIV, adverse effects are mild; rhinorrhea is the most common, and mild wheezing may occur.

More Information

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Also of Interest

Videos

View All
Overview of Tuberculosis (TB)
Video
Overview of Tuberculosis (TB)
3D Models
View All
SARS-CoV-2
3D Model
SARS-CoV-2

SOCIAL MEDIA

TOP