For more information, see Influenza ACIP Vaccine Recommendations and Centers for Disease Control and Prevention: The Pink Book: Influenza.
Based on recommendations by the WHO and 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.
There are 2 basic types of vaccine:
Trivalent vaccines are gradually being superseded by quadrivalent vaccines that cover an additional B virus strain.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 yr.
Annual vaccination against influenza is recommended for
IIV can be given to all people ≥ 6 mo, including pregnant women.
IIV may be given to people with a history of mild egg allergy (ie, who have experienced only hives after exposure to eggs) if extra safety precautions are taken. A clinician who is familiar with the diagnosis and treatment of allergic reactions should give the vaccine to these people, and the clinician must observe them for 30 min after vaccination.
An age-appropriate formulation should be used.
Adults ≥ 65 yr should be given high-dose IIV. The high dose is recommended only for those ≥ 65 yr.
RIV3 can be used in people aged 18 to 49 yr who have any degree of egg allergy and who have no other contraindications to the vaccine.
LAIV can be given to healthy people aged 2 to 49 yr who are not pregnant and who do not have immunocompromising conditions. 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).
The main contraindication for IIV is
Precautions with IIV include
Contraindications for LAIV include
A severe allergic reaction (eg, anaphylaxis) after previous dose of any influenza vaccine or to a vaccine component, including egg protein
Immunocompromise (eg, due to disorders, including HIV infection, or use of immunosuppressants)
Certain chronic disorders (eg, asthma; reactive airway disease; diabetes; hemoglobinopathy; lung, heart, or kidney disorders)
For children and adolescents, long-term treatment with aspirin or other salicylates
Age < 2 yr or ≥ 50 yr
Age < 5 yr if reactive airway disease (eg, known asthma, recurrent or recent wheezing episodes) is present
Precautions for LAIV include
Moderate or severe acute illness with or without fever (vaccination is postponed until illness resolves)
Guillain-Barré syndrome within 6 wk after a previous dose of an influenza vaccine
Use of specific antiviral drugs: ie, amantadine, rimantadine, zanamivir, oseltamivir (these drugs are stopped 48 h before vaccination and are not resumed for 14 days after vaccination)
The main contraindication for RIV3 is
Precautions for RIV3 include:
The influenza vaccine is given yearly.
For IIV, the dose is
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.
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 (see Anti-Vaccination Movement : Thimerosal and autism); 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.