By; Nikunj Vyas, PharmD Candidate c/o 2012
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Seasonal flu vaccines protect us against the three influenza viruses that researchers predict will be the most common viral strains during the flu season. The viruses in the vaccine change each year based on international surveillance and scientists‘ estimations about the types and strains of viruses that will circulate in a given year. About two weeks after vaccination, the human body produces antibodies that provide protection against the influenza viruses in the vaccine.
The Centers for Disease Control and Prevention (CDC) recommends that people get their seasonal flu vaccine as soon as the vaccine becomes available in their community, preferably before December. The CDC continues to encourage people to get vaccinated throughout the flu season, which can begin as early as October and end as late as May. Over the course of the flu season, many different influenza strains can circulate at different times and in different regions of the country. But as long as there is a flu season, vaccination can provide the necessary protective benefits. Everyone six months and older should get a flu vaccine each year, starting with this 2011-2012 influenza season.
There are three available flu vaccines: a regular flu vaccine indicated for ages 6 and older (Fluzone), a high dose flu vaccine approved for ages 65 and older (Fluzone High-Dose), and an intradermal flu vaccine for ages 18 to 64 (Fluzone Intradermal).
Our immune system weakens with age, and we may have an inappropriate immune response following vaccination. Thus, Fluzone High-Dose, manufactured by Sanofi Pasteur Inc., contains four times the amount of antigen (the part of the vaccine that prompts the body to make antibody) contained in a regular flu shots. In the elderly, this additional antigen is intended to produce a stronger immune response and better protection against seasonal flu. Conversely, Fluzone Intradermal requires a much smaller needle than the regular flu shot, as well as fewer antigens (while remaining as effective as the regular flu shot).
Clinical trials compared Fluzone to Fluzone High-Dose among persons aged 65 years or older, and their results indicated that a stronger immune response (higher antibody levels) occurred after vaccination with Fluzone High-Dose. It is unknown if the improved immune response led to greater protection against influenza disease after vaccination.
An ongoing study designed to determine the effectiveness of Fluzone High-Dose in preventing illness from influenza compared to Fluzone is expected to be completed in 2014-2015. The safety profile of Fluzone High-Dose vaccine is similar to that of regular flu vaccines, although adverse events were reported more frequently after vaccination with Fluzone High-Dose compared to the regular flu vaccine. The most commonly ones were mild and temporary, including injection site reactions (pain, redness, and swelling), headache, muscle aches, fever, and malaise. On the whole, most people had minimal or no adverse events after receiving the Fluzone High-Dose vaccine. Of course, patients with a severe allergic reaction (e.g. anaphylaxis) to any component of the vaccine, including egg protein, or to a previous dose of any influenza vaccine, should not receive Fluzone, Fluzone High-Dose, or Fluzone Intradermal.
Finally, Fluzone High-Dose is available as a 0.5 mL preservative-free, single dose, prefilled syringe. It needs to be shaken before administration, and exactly 0.5 mL is administered into the deltoid muscle of the upper arm. Further administration instructions can be found within the package insert.
Neither CDC nor ACIP expresses a preference of one vaccine over another at this time, but to remain safe this season, it is highly recommended to get the flu shot!
SOURCES:
- Centers for Disease Control and Prevention. Fluzone High-Dose Seasonal Influenza Vaccine. Available at http://www.cdc.gov/flu/protect/vaccine/qa_fluzone.htm. Accessed October 30, 2011.
- Greider, K. The New Flu Shot for Older Americans: An-swers to Your Questions. AARP Bulletin 10/14/2010.
- Available at http://www.aarp.org/health/conditions-treatments/info-10-2010/the_new_flu_shot_for_older_americans_answers_to_your_questions_.html. Accessed October 30, 2011.
