Are You Prepared for This Year’s Flu Season?

Primary Care Update
Brief Summaries for Clinical Practice

Does your patient who received last year’s influenza vaccine need to be revaccinated this fall? What about a child who was given 1 dose of vaccine last year—will 1 dose suffice this year?

The 2011–2012 US seasonal influenza vaccine virus strains are identical to those contained in the 2010–2011 vaccine. These include A/California/7/2009 (H1N1)-like (Figure), A/Perth/16/2009 (H3N2)-like, and B/Brisbane/60/2008-like antigens. Although the strains remain unchanged from the previous season, annual vaccination is still advised for those who received the vaccine last year.¹

WHO SHOULD RECEIVE
THE 2011–2012 VACCINE?
Routine vaccination is recommended for all persons aged 6 months and older (Table). Children aged 6 months through 8 years should be given 2 doses of influenza vaccine (administered a minimum of 4 weeks apart) during their first season of vaccination to optimize immune response. Note that in previous years children aged 6 months through 8 years who received only 1 dose of influenza vaccine in their first year of vaccination required 2 doses the following season. However, because the 2011–2012 vaccine strains are unchanged from last year, children in this age group who received at least 1 dose of the 2010–2011 seasonal vaccine will require only 1 dose of this year’s vaccine. If a child in age group did not receive at least 1 dose of the 2010–2011 vaccine or if it is unclear whether the vaccine was received, 2 doses of the 2011–2012 seasonal influenza vaccine should be given.

AVAILABLE VACCINE
PRODUCTS
Several influenza vaccines will be available during the 2011–2012 season, and all of them contain the same antigenic composition. Consult the package inserts for more information about additional components of the various vaccine formulations. 

Trivalent inactivated vaccine (TIV) preparations, with the exception of Fluzone Intradermal (Sanofi Pasteur), should be administered intramuscularly. For adults and older children, the deltoid is the preferred site. Infants and younger children should be vaccinated in the anterolateral thigh.

A new TIV preparation, Fluzone Intradermal, is administered intradermally. This vaccine is indicated for persons aged 18 through 64 years and contains less antigen than intramuscular TIV preparations (9 µg rather than 15 µg of each strain per dose) in a smaller volume (0.1 mL rather than 0.5 mL).

The vaccine is given via a single-dose, prefilled microinjection syringe. The preferred site of administration is over the deltoid muscle.² The most common adverse reactions include injection-site erythema, induration, swelling, pain, and pruritus. Except for pain, these reactions occurred more frequently than with intramuscular vaccine, but they generally resolved within 3 to 7 days. This vaccine is an alternative to other TIV preparations for persons aged 18 through 64 years, with no preferential recommendation.

An alternative TIV for persons aged 65 years and older is Fluzone High-Dose (Sanofi Pasteur).
This vaccine contains 60 µg of hemagglutinin per vaccine strain (rather than 15 µg per strain as in other intramuscular TIV preparations). No preference is indicated for this TIV versus other TIV
preparations. 

The intranasally administered live attenuated influenza vaccine (LAIV) FluMist (MedImmune) is indicated for healthy, nonpregnant persons aged 2 through 49 years. Within the patient groups specified for each vaccine in the package inserts, no preference is indicated for LAIV versus TIV.

WHEN TO GIVE THE VACCINE
Start offering the influenza vaccine as soon as it becomes available—even as early as August—to allow time for the production of protective antibody levels. Continue vaccination efforts throughout the duration of the influenza season. Vaccine administered in December or later, even if influenza activity has already begun, is likely to be beneficial during most influenza seasons. While influenza outbreaks can occur as early as October, disease activity typically peaks in January or later.

NEW GUIDELINES FOR PATIENTS
WITH EGG ALLERGY
The 2011 guidelines for influenza vaccination in persons with egg allergy are more permissive than in previous seasons. In several recent studies, persons with egg allergy have tolerated administration of both full doses and split doses of TIV without serious reactions.¹ The Advisory Committee on Immunization Practices (ACIP) now recommends that 

for the 2011–2012 influenza season, persons who have experienced only hives from consuming eggs can receive TIV intramuscularly as long as they are treated by a health care provider who is familiar with the potential manifestations of egg allergies and can be observed by a health care professional for at least 30 minutes after receiving each dose. LAIV should not be used in these patients.

Some persons who report allergy to egg might not actually be allergic to eggs. Those who are able to eat lightly cooked egg (eg, scrambled eggs) without reaction are unlikely to be allergic. However, egg-allergic persons might tolerate egg in baked products (eg, bread or cake); thus, tolerance to egg-containing foods does not exclude the possibility of egg allergy.³ Such allergy can be confirmed by a consistent medical history of adverse reactions to eggs and egg-containing foods, in addition to skin and/or blood testing for immunoglobulin E antibodies to egg proteins.

Persons who have had reactions to egg involving angioedema, respiratory distress, lightheadedness, or recurrent emesis, or persons who required epinephrine or other emergency medical intervention (particularly reactions that occurred immediately or within minutes to hours after egg exposure) are more likely to have a serious systemic or anaphylactic reaction on re-exposure to egg proteins. Before vaccination, such persons require further risk assessment by a physician who has expertise in the management of allergic conditions. 

In general , the ACIP recommends that all vaccines be administered in settings in which personnel and equipment for rapid recognition and treatment of anaphylaxis are available. A previous severe allergic reaction to influenza vaccine, regardless of the component suspected to be responsible for the reaction, is a contraindication to vaccination. ■