Updated Influenza Vaccine Recommendations Issued by CDC on 18 August 2011

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3D Influenza virus: Image courtesy of the California DHS, NIH

The 2011-2012  vaccination guidelines from the Center for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) are summarized below.

Annual influenza vaccination is still recommended for everyone 6 months of age and older.

To provide enough time for production of protective antibody levels, CDC says that vaccination is best administered early, before the onset of influenza in the community. Thus they urge that immunization is provided as soon as vaccine as available and continue to be offered throughout the influenza season.

The 2011-12 vaccine strains of influenza virus are identical to those in the 2010-2011 vaccine. 

These include A/California/7/2009 (H1N1)-like, A/Perth/16/2009 (H3N2)-like, and B/Brisbane/60/2008-like antigens. CDC notes that the influenza A (H1N1) vaccine strain is derived from a 2009 pandemic influenza A (H1N1) virus.

Note: “H” stands for hemagglutinin and “N” for neuraminidase – proteins on the influenza virus’ surface that scientists use to differentiate one type of influenza virus from another.

Although the influenza vaccine strains for this season are the same as last year, optimal protection demands annual vaccination.

Children 6 months of age to 8 years old who were not immunized last year should receive 2 doses of the vaccine administered a minimum of 4 weeks apart. This scheduling, says CDC, provides the best protective antibody responses. However, if a child is known to have received at least 1 dose of the 2010-2011 vaccine, then only one dose of this year’s vaccine is needed. CDC cautions, however, that 2 doses should be given if there is any uncertainty whether or not immunization was administered last year.

CDC expects a number of influenza vaccines to be available; all contain the same antigen mix.

All but one trivalent inactivated (TIV) vaccine are injected into the muscle. The only exception is a new TIV vaccine that can be injected under the skin, Fluzone Intradermal, which is only indicated for people aged 18 through 64 years and contains less antigen than intramuscular TIV preparations. Fluzone High-Dose is available as an alternative TIV for people older than 65 years who may not mount as robust an immune response as younger individuals.

An intranasally administered live attenuated vaccine called FluMist is also available but should only be given to healthy, non-pregnant people aged 2 through 49 years.  For the appropriate vaccine recipients, says CDC, “no preference is indicated for LAIV versus TIV.”

In addition to Fluzone and FluMist made by Sanofi Pasteur and Medimmune respectively,  Fluvirin (Novartis), Fluarix (GlaxoSmithKline), FluLaval (ID Biomedical Corporation)and Afluria (CSL Biotherapies) are expected to be available during this influenza season.

Allergy to eggs must be distinguished from allergy to influenza vaccine.

All currently available vaccines are made by growing the viruses in chicken eggs, thus hypersensitivity to eggs has been a contraindication to influenza immunization.  However, CDC cites several recent studies showing that TIV has been safely administered to people with egg allergy. As a consequence, there have been revisions to some of the TIV package inserts noting that only severe allergic reactions – anaphylaxis —to egg protein is a contraindication.

Furthermore, not everyone who thinks they’re allergic to eggs really is. For example, people who can eat lightly cooked egg (e.g. scrambled eggs) without a reaction are unlikely to be allergic. Conversely, tolerance to egg-containing foods such a breads or cakes, does not exclude the possibility of an egg allergy. Confirmation requires a consistent medical history of adverse reactions to eggs plus skin and/or blood testing for antibodies to egg proteins.

CDC also notes that severe allergic reactions can occur to other components in influenza vaccine, “but such reactions are rare,” they add.  However, “A prior severe allergic reaction to influenza vaccine, regardless of the component suspected to be responsible for the reaction, is a contraindication to receipt of influenza vaccine.”

Recommendations for vaccine use in people with egg allergy.

People who only develop hives after exposure to eggs should be immunized against influenza but with the following safety measures:

  • Because published studies only investigated TIVs, these rather than the LAIV (FluMist) vaccine should be used.
  • Vaccine should be administered by a health-care provider who is familiar with egg allergy.
  • People likely to have a reaction to eggs should be watched for at least 30 minutes after receiving the vaccine for signs of a reaction.

Other measures, for example, dividing and administering the vaccine in two doses or skin testing are not considered necessary by CDC.

People who have had severe reactions to egg as, for example, respiratory distress, lightheadedness or recurrent vomiting, or those who have required epinephrine or other emergency medical interventions should be referred to a physician with expertise in the management of severe allergies for risk assessment. Notably, influenza is a deadly disease and the risks of  immunization versus the benefits should be carefully evaluated.

Sources:

CDC. Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. In MMWR; 60, (Early Release).

CDC. Prevention and control of influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2010. MMWR; 59, (No. RR-8).

Additional Information:

Information about seasonal influenza from CDC.

CDC’s suggestions for fighting the flu.

“FluView,” a weekly update on influenza from CDC.

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