Flu Vaccine FAQ & Misconceptions

By Nan Laoprasert, MD

dr_laoprasertSince the flu season is in progress, we reprint a part of the article that appeared in last spring’s newsletter to address FAQ’s and misconceptions about the influenza vaccine and to review recent information regarding the influenza vaccine in egg allergic patients. Most of this information and more can be found on the CDC web site at www.cdc.gov/flu.

When is the ideal time to get the flu vaccine?

The influenza vaccine season in Colorado is variable. It has been known to occur as early as August and as late as May. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza. To ensure that as many people as possible are protected before the flu season begins, the CDC recommends that influenza vaccination begins as soon as the vaccine becomes available, even as early as August, and continues throughout the flu season. Flu activity usually peaks in January or February in the United States and can last as late as May. As long as the flu season isn’t over, it’s not too late to get vaccinated.

Can the flu vaccine give me the flu?

This is a common misconception. No, the flu vaccine cannot give you the flu. The influenza vaccine is an inactivated, killed vaccine and does not cause the flu. It can cause some nonspecific, mild symptoms including muscle aches, local redness and fever for one or two days after vaccination. These side effects usually reflect your body’s production of protective antibodies.

FluMist, a nasal spray vaccine, contains a low dose of live, weakened flu viruses. It does not cause the flu and is generally well tolerated. It is recommended for use in healthy people 2-49 years of age who are not pregnant. It can cause nasal congestion, sore throat and clear nasal drainage. It is not recommended in children less than 2 years old and in patients with asthma because of an increased risk of wheezing.

Although I am not allergic to egg, I developed a generalized reaction to the flu vaccine last year and therefore should not receive any more flu vaccinations.

An allergy to egg must be distinguished from an allergy to the influenza vaccine. A prior severe allergic reaction to the influenza vaccine, regardless of the components suspected to be responsible for the reaction, is a contraindication to receiving a future influenza vaccine. An evaluation by an allergist is recommended, as some flu vaccine components triggering reactions are also present in other vaccines and can be identified.

I am allergic to egg and therefore should not receive the flu vaccine.

Both inactivated as well as live, weakened influenza vaccines are made from viruses grown in eggs and therefore contain a small amount of egg protein. In individuals allergic to egg, hypersensitivity reactions to egg protein can therefore occur. Fortunately, recent studies have shown that almost all patients allergic to egg can safely receive the flu vaccine. As all these studies were done with the injectable trivalent inactivated vaccine, egg allergic patients should receive the trivalent inactivated vaccine rather than the live attenuated influenza vaccine. It is reassuring that almost all inactivated vaccines now contain minimal amount of egg protein. Flublok (recombinant influenza vaccine, trivalent) is considered egg-free and is licensed for use in 18 years and older.

Information from recent studies has led both the CDC and the American Academy of Pediatrics to release new Guidelines regarding administration of the flu vaccine in egg allergic patients.

These guidelines stress that the risks of vaccinating egg allergic patients with the influenza vaccine are less high than the risks of not vaccinating. This is true even for patients with a history of anaphylaxis to egg. All egg allergic patients should receive influenza vaccine in a setting where anaphylaxis can be recognized and treated and should be observed for 30 minutes after vaccination. In all egg allergic patients, we advise yearly reevaluation of their egg allergy by history and skin testing, which can be accomplished during the same office visit as their yearly influenza vaccination visit.

Individuals who report a history of hives after egg ingestion should be observed for at least 30 minutes following vaccination to watch for any sign of an allergic reaction. Evaluation of their suspected egg allergy by an allergist is strongly recommended but need not delay the vaccination, which can occur in their general physician’s office. The new guidelines recommend referral to an allergy specialist prior to vaccination for patients with a history of a more severe reaction to egg. Some of the symptoms include: swelling (angioedema), respiratory distress, lightheadedness, recurrent vomiting, or who require epinephrine or another emergency medical intervention. These patients are more likely to develop a serious systemic or anaphylactic reaction to the flu vaccine. Growing data suggest that skin testing to the vaccine prior to vaccination and division of the vaccination dose may no longer be required even in these severely allergic patients.