Insights on Influenza Blog
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Types of Flu Vaccines

While there are different types of flu vaccines available, for most people simply getting the flu vaccine — any flu vaccine — is what matters most.

Generally speaking, the type of flu vaccine you receive is decided by the location of where you receive your vaccine. However, people should understand that there are different ways that flu vaccines are manufactured, and different types of vaccines that may be more appropriate for some people based on their age, medical conditions, or medical history.

Quadrivalent Inactivated Influenza Vaccines (IIV4)

Quadrivalent Inactivated Influenza Vaccines (IIV4)

The most commonly administered flu vaccine is a quadrivalent vaccine, which provides protection against the four strains of influenza most likely to be circulating each season.


Trivalent Inactivated Influenza Vaccines (IIV3)

Trivalent Inactivated Influenza Vaccines (IIV3)

These flu vaccines are similar to the quadrivalent vaccines, but only provide protection against three strains of influenza (as opposed to four with a quadrivalent vaccine). The only currently available trivalent flu vaccines include a high-dose vaccine and an adjuvanted vaccine, both of which are only approved for people 65 years of age and older.


nasal spray flu vaccine

Quadrivalent Live Attenuated Influenza Vaccine (LAIV4)

Nasal Spray Flu Vaccine

This vaccine is administered intranasally, which means that the vaccine is sprayed up the nose as opposed to being injected with a needle. 

This vaccine can be used in individuals ages 2 through 49 years and can be a good option for people who avoid flu vaccination due to a fear of needles. The vaccine is known as “live attenuated” because it includes minuscule bits of weakened, live viruses that are modified in such a way that they can replicate in the nose to create an immune response. However, they can not replicate in the warm conditions of the lungs, which means the vaccine can not result in flu infection.

At the onset of the 2018-2019 flu season, the American Academy of Pediatrics (AAP) had recommended flu shots over the nasal spray for kids, based on some evidence that nasal spray flu vaccine didn’t work particularly well during the 2013-2014 and 2015-2016 seasons.  However, the manufacturer has since reformulated the nasal spray vaccine and both the AAP and the Centers for Disease Control and Prevention currently support this vaccine as an option for annual flu vaccination for children age 2 years and older who do not have contraindications.

Influenza vaccination and fear of needles

Piper had not been vaccinated against the flu because she did not like needles. Her mother, Pegy, is now an active advocate for annual flu vaccinations.

Read Piper's Story


Quadrivalent Recombinant Influenza Vaccine (RIV4)

Quadrivalent Recombinant Influenza Vaccine (RIV4)

These vaccines are produced in a way that is slightly different than other vaccines and do not use chicken eggs in the manufacturing process.  They are the only egg-free vaccine currently available in the U.S. and are licensed by the FDA for use in adults 18 years and older. Because these vaccines are not dependent on an egg supply or limited by the selection of vaccine viruses that are adopted for growth in eggs, recombinant vaccines can be useful in the event of a pandemic or vaccine supply shortage.
Kathy Pool, protect your family with flu vaccination

Kathy Pool encourages other grandparents to get a flu vaccine specifically designed for seniors to protect themselves and everyone they love from going through what her granddaughter, Caroline, experienced.

Read Caroline's Story

Flu Vaccines for Seniors

As our body ages, so does our immune system. That is why there are specially formulated vaccines available for individuals who are 65 years and older.

These vaccines are designed to induce a greater immune response so that the body produces enough antibodies to protect the recipient. One type of flu vaccine specifically designed for seniors is the Fluzone High-Dose vaccine, which prompts the body with four times the number of viral particles contained in other vaccines. The other vaccine specifically designed for seniors, Fluad, contains a compound called an adjuvant, which induces the immune system to react more forcefully to the injection. Both of these vaccines can be used in adults age 65 years and older.

One study on the high-dose flu vaccine found that adults age 65 years and older had 24 percent fewer influenza infections as compared to those who received a standard flu vaccine. One study on the adjuvanted flu vaccine found it was 63 percent more effective than regular dose unadjuvanted flu shots. While the increased amount of protection may vary, experts agree that individuals 65 years of age and older should consider getting a flu vaccine specifically designed for seniors each season. Talk to your trusted healthcare professional about which one may be right for you.

Find out why it’s especially important for adults who are 65 years of age and older to get their annual flu vaccines by visiting our Seniors page.

Talk to your health care provider about which vaccine is best for you.

3 Ways Flu Vaccines are Manufactured:

Egg-based vaccines

Egg-Based Flu Vaccines

The egg-based vaccine manufacturing process has been used for more than 70 years. This process is used to make many of the inactivated flu vaccines (i.e., flu shots) as well as the live attenuated influenza vaccine (LAIV, or the nasal spray flu vaccine). The manufacturing process begins with the Centers for Disease Control and Prevention (CDC) or the World Health Organization (WHO) providing egg-grown candidate vaccine viruses (CVVs) to manufacturers. These CVVs are then injected into fertilized chicken eggs and allowed to replicate. The virus-containing fluid is then harvested from the eggs. For flu shots, the vaccine viruses are then inactivated and the virus antigen is purified. The manufacturing process continues with purification and testing. For LAIV, the starting CVVs are weakened viruses and go through a different production process. The U.S. Food and Drug Administration (FDA) tests and approves vaccines prior to release and shipment.

Even individuals with confirmed egg allergy can safely receive egg-based flu vaccines. The American Academy of Allergy Asthma and Immunology, the American College of Allergy Asthma and Immunology as well as the American Academy of Pediatrics and the CDC state that no special precautions are required for the administration of influenza vaccine to egg-allergic patients. Learn more about the safety of flu vaccines for people with egg allergies.

Cell-based vaccines

Cell-Based Flu Vaccines

The cell-based vaccine manufacturing process uses animal cells in liquid culture to grow influenza viruses in place of fertilized chicken eggs. The manufacturing process begins when the World Health Organization (WHO) recommends cell-grown candidate vaccine viruses (CVVs) for distribution to manufacturers. The manufacturers then inoculate these CVVs into cultured mammalian cells (instead of eggs) and allow them to replicate for a few days. Then the virus-containing fluid is collected from the cells and the virus antigen is purified. The manufacturing process continues with purification and testing before the U.S. Food and Drug Administration (FDA) tests and approves the vaccines prior to release and shipment.

Recombinant Flu Vaccines

Recombinant Flu Vaccines

The recombinant manufacturing process does not use chicken eggs at all in the production process. Instead, manufacturers isolate a certain gene from a naturally occurring "wild type" recommended vaccine virus. The gene is then combined with portions of another virus that grows well in insect cells to make a "recombinant" vaccine virus. The vaccine virus is then mixed with insect cells and allowed to replicate. The flu protein is then harvested from these cells, purified, and submitted for testing and approval to the U.S. Food and Drug Administration (FDA) prior to release and shipment.


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Page last reviewed: May 2020. 

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