This is a quick run down of some of the most frequent questions I am asked about the “flu” vaccine.

Can the flu shot give me the flu? 

No it cannot. I hear people say that the flu shot gave them the flu all the time but the reality is that the flu vaccine is 1. not a live virus or 2. does not contain virus particles (aka recombinant) therefore it cannot give you the flu. However, people might get mild fever, pain/soreness/redness at injection site, and headache.

The nasal spray, also known as LAIV, is different from the shot. The nasal spray does contain weakened live flu virus. Although rare, clinical studies have shown that close contacts of those receiving the nasal spray flu vaccine have become infected. The weakened virus in the nasal spray may cause runny nose, headache, cough, and sore throat. Additionally, wheezing and fever have been observed in children.

I got the flu shot but still got the flu, how can this happen?

The “flu shot” is actually a prediction. Based on research and history, the CDC will  predict which versions of influenza will be most commonly circulating. There are two types trivalent and quadrivalent. Trivalent means the shot contains 3 components (an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus) while the quadrivalent contains 4 (an influenza A (H1N1) virus, an influenza A (H3N2) virus, and two influenza B virus).  Influenza is a virus and viruses are constantly changing. Due to these changes, a person may come into contact with a version of the flu to which he/she is not vaccinated. So yes it is possible to get the flu even though you have been vaccinated.

“All of the 2014-2015 influenza vaccine is made to protect against the following three viruses:

  • an A/California/7/2009 (H1N1)pdm09-like virus
  • an A/Texas/50/2012 (H3N2)-like virus
  • a B/Massachusetts/2/2012-like virus.

Some of the 2014-2015 flu vaccine also protects against an additional B virus (B/Brisbane/60/2008-like virus).” (source)

How are flu shots made?

Egg-based, the most common method, is used in both the flu “shot” and the nasal spray. The flu virus is injected into a fertilized hen egg and allowed to replicate. The virus containing fluid of the egg is then harvested and ran through many levels of purification.

Cell-based methods inject the virus into mammalian cells (not hen eggs) and allow the virus to replicate. Then, like the egg based method, the virus containing fluid is harvested and undergoes a multitude of purification steps. As of right now, there is only one cell-based product available in the US: Flucelvax. Flucelvax is trivalent and inactivated.  Cell-based vaccines have been approved for use in a number of European countries.  The viruses used in this process however begin as egg-grown vaccine viruses.

Both egg-based and cell-based methods are referred to as IIV or inactivated influenza vaccine.

Recombinant flu vaccines separate the HA protein of the “wild” or naturally occurring virus. That protein is then combined with portions of another virus known to grow well in insects. That combined virus is then mixed with insect cells and allowed to replicate and grow. The HA protein is then harvested and purified.  According to the CDC, “recombinant flu vaccine is the only 100% egg-free vaccine on the U.S. market” (source)  Flublok  is the only approved recombinant vaccine in the US; it is also known as RIV3.

Can a person with egg allergy get the flu vaccine?

First and foremost, if you have any reaction to eggs, do not go to your local retail pharmacy. You will be turned away. Retail pharmacy protocol will not allow individuals with a history of egg allergy to be vaccinated. If the vaccine is indicated and recommended based on your personal history, go to an allergist for administration.

The Advisory Committee on Immunization Practices (ACIP)  “recommends the following:

  1. Persons with a history of egg allergy who have experienced only hives after exposure to egg should receive influenza vaccine. Because relatively few data are available for use of LAIV in this setting, IIV or trivalent recombinant influenza vaccine (RIV3) should be used. RIV3 may be used for persons aged 18 through 49 years who have no other contraindications. However, IIV (egg- or cell-culture based) may also be used, with the following additional safety measures (Figure 2):
    • Vaccine should be administered by a health care provider who is familiar with the potential manifestations of egg allergy; and
    • Vaccine recipients should be observed for ≥30 minutes for signs of a reaction after administration of each vaccine dose.
  2. Persons who report having had reactions to egg involving such symptoms as angioedema, respiratory distress, lightheadedness, or recurrent emesis; or who required epinephrine or another emergency medical intervention, may receive RIV3 if they are aged 18 through 49 years and there are no other contraindications. If RIV3 is not available or the recipient is not within the indicated age range, IIV should be administered by a physician with experience in the recognition and management of severe allergic conditions (Figure 2).
  3. Regardless of allergy history, all vaccines should be administered in settings in which personnel and equipment for rapid recognition and treatment of anaphylaxis are available (29).
  4. Persons who are able to eat lightly cooked egg (e.g., scrambled egg) without reaction are unlikely to be allergic. Egg-allergic persons might tolerate egg in baked products (e.g., bread or cake). Tolerance to egg-containing foods does not exclude the possibility of egg allergy. Egg allergy can be confirmed by a consistent medical history of adverse reactions to eggs and egg-containing foods, plus skin and/or blood testing for immunoglobulin E directed against egg proteins (30).
  5. For persons with no known history of exposure to egg, but who are suspected of being egg-allergic on the basis of previously performed allergy testing, consultation with a physician with expertise in the management of allergic conditions should be obtained before vaccination (Figure 2). Alternatively, RIV3 may be administered if the recipient is aged 18 through 49 years.
  6. A previous severe allergic reaction to influenza vaccine, regardless of the component suspected of being responsible for the reaction, is a contraindication to future receipt of the vaccine.”

I quoted this directly from the CDC’s Morbidity and Mortality Weekly Report dated August 15, 2014 . (source)

Translation:  The nasal spray  (LAIV) is not recommended in patient’s with a history of egg allergy  (any severity) while the inactivated influenza vaccines may be administered to patients with a history of hives only egg allergy (again not at a retail pharmacy). Any egg-allergy severity above hives only should be referred to an allergist for further evaluation.

Recombinant vaccines are 100% egg free and can be given to any level of egg-allergic individuals.  Each vaccine has its own set of approved age ranges as well which will be taken into consideration prior to administration.

Anaphylaxis in egg allergic individuals has been reported to the Vaccine Adverse Event Reporting System (VAERS) after flu vaccine administration.


And another question that is important at this time (one that pharmacists have been getting in retail pharmacies across the country):

Will this protect me from Ebola?

No. Ebola is not a strain of influenza although both are viruses.  The early signs and symptoms of Ebola are the same as the flu however:  fever, chills, muscle/joint aches,  headache, sore throat and weakness.


Please see my Influenza Vaccine Chart 2014-2015 for manufacturer specific information.