Types of Flu Vaccines
Learn which flu vaccines are best for you based on your age and medical conditions.
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.
These flu vaccines provide protection against three strains of influenza (as opposed to four with a quadrivalent vaccine). There are no trivalent vaccines for the 2021-2022 flu season.
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 without infecting you with a flu illness. Some people do not qualify for the nasal spray vaccine.
As our body ages, so does our immune system. That is why there are specific vaccines for individuals 65 years and older to create a stronger immune response against the flu.
Talk to your health care provider about which vaccine is best for you.
3 Ways Flu Vaccines are Manufactured:
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.
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.
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.
Page last reviewed: October 2021.