Feature Article: Understanding Types of Influenza Vaccines

Published on in Parents PACK

Getting a seasonal influenza vaccine provides the best protection available against what can be a severe, and even deadly, disease. The vaccine typically protects about 70 of 100 vaccinated people from being infected with influenza and often lessens the length and severity of the disease for those who do become infected. While the recommendation to get an influenza vaccine is well understood, the different types of influenza vaccines available may require additional information.

The first influenza vaccine was licensed in the U.S. in 1945. Through the years, advancements in vaccine research and manufacturing have resulted in a few different influenza vaccine options. Below is a summary of the different influenza vaccines now available.

Inactivated influenza vaccines (IIV) – “the shot”

The traditional influenza vaccine is made by growing influenza viruses in eggs, purifying the viruses, and then completely killing the viruses with a chemical so that they cannot replicate and, therefore, cannot cause disease. Versions of the influenza shot contain three or four strains of influenza virus. The inactivated version, given as a shot into a muscle, is the version most people receive. It is made by multiple companies, so it is distributed under a variety of product names and brands. Possible side effects include redness, soreness or hardening at the injection site, muscle aches or a low-grade fever.

Several special preparations of the inactivated influenza vaccine are also available:

  • Intradermal: This version uses a significantly smaller needle than the traditional needle used for intramuscular delivery. The smaller needle is injected into the skin rather than into the muscle. The intradermal injection uses lesser quantities of influenza virus proteins, but can cause more local reactions like pain or redness at the injection site. The intradermal vaccine (Fluzone® Intradermal) is used in people 18 years of age and older.
  • Cell-derived: This version of influenza vaccine is grown in mammalian cells, not eggs. Because eggs are not used to grow the vaccine viruses, vaccine prepared in this manner can be made more quickly (two months versus at least six months for an egg-based influenza vaccine). This type of production also means lower quantities of egg proteins in the final product, so it can be given to people with moderate to severe egg allergies. This version is used in people 18 years of age and older.
  • Recombinant DNA: In this version, a gene for an influenza virus surface protein (called hemagglutinin) is inserted into a small, circular piece of DNA (a plasmid), which is then reproduced inside insect cells. As the cells reproduce, the influenza protein is also produced. The protein is then purified and used as the vaccine. FluBlok® is the only completely egg-free influenza vaccine available in the U.S. making it ideal for use in those with severe egg allergies. This vaccine is made with the shortest production time and is licensed for use in people 18 years of age and older.
  • High-dose: This version is specifically designed for use in people 65 years of age and older. It contains four times more of the influenza virus protein (hemagglutinin) than other formulations in an effort to induce better immune responses in older people whose immune systems may not respond as well. Recently, the high-dose influenza vaccine was shown to decrease hospitalizations compared with the standard dose vaccine in older patients. Therefore, it is the best vaccine for people 65 years of age and older.

Live attenuated influenza vaccine (LAIV) – “the nasal spray”

Editor’s note: In July 2016, the Centers for Disease Control and Prevention (CDC) recommended against using the live attenuated nasal spray influenza vaccine during the 2016-2017 influenza season. The recommendation was made due to ineffectiveness of the vaccine during the previous few seasons and, not vaccine safety concerns. 
Learn more about the decision.

The intranasal version of the influenza vaccine contains live, weakened influenza viruses that have been grown repeatedly in the laboratory, so that instead of replicating at body temperature, they are better able to replicate in the comparably cooler temperatures of the nasal cavity. Because the vaccine virus cannot grow at normal body temperature, it can’t possibly cause the pneumonia that is occasionally a consequence of natural infection. The nasal spray influenza vaccine provides protection against four types of influenza. It is approved for use in healthy people between the ages of 2 years and 49 years. Possible side effects include runny nose, mild congestion, sore throat and cough.

Although understanding the different types of the vaccine may be confusing, the important thing to know is that this variety enables healthcare professionals to safely vaccinate virtually anyone who requests an influenza vaccine. And, for virtually everyone, receiving a seasonal influenza vaccine is the best defense against this unpredictable, and potentially deadly, pathogen.

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.