According to the Centers for Disease Control and Prevention (CDC), getting immunized for influenza each year is your best bet for avoiding the flu. However, the vaccine is not for everyone, especially people with allergies. Knowing the ingredients of the flu vaccine can help you and your health care provider determine whether or not you are a candidate for vaccination.
Virus
According to the CDC, the flu shot contains inactivated influenza virus while intranasal vaccines such as FluMist supply "attenuated" virus. Inactivated virus has been treated with formaldehyde or beta-propionolactone so that it is no longer capable of causing infection. (Technically, viruses are never alive, so the vaccine cannot be called "killed" like bacterial vaccines are.) The virus in FluMist is attenuated or weakened, which means that it cannot produce classic influenza illness, and cold-adapted, which means that it does not grow well at body temperature.
The seasonal flu vaccine is a "trivalent" vaccine which means it contains three influenza viruses. Although the individual strains vary each year, the types of strains selected for the vaccine usually consist of an influenza A strain, an H1N1 strain (not the pandemic 2009 strain) and an influenza B strain. In 2009, the FDA also approved a "monovalent," or single strain, vaccine designed exclusively to combat the pandemic H1N1 strain.
Trace Ingredients
Flu vaccine may contain traces of compounds used in the manufacturing process. All flu vaccines are grown in fertilized chicken eggs. Egg protein has been reported in concentrations up to 0.000001 grams. Antibiotics such as kanamicin, gentamicin, neomycin and polymixin B are often used to prevent bacterial contamination of the chicken eggs. Residual amounts of these may be present in the final vaccine. For the 2009-2010 season, Sanofi Pasteur (Fluzone) and ID Biomedical (Flulaval) did not use antibiotics in their seasonal flu or H1N1 vaccines.
Detergents are used to separate the virus from components of the eggs. Examples of detergents used in the 2009-2010 vaccine include sodium taurodeoxycholate, polyethylene glycol p-isooctylphenyl ether and octoxynol-10. These are usually measured in terms of parts per million. Each manufacturer specifies the maximum concentration of the specific type of detergent used in their brand.
Buffer Solution
According to the Food and Drug Administration and the manufacturers' product literature, H1N1/09 and seasonal flu injection vaccines are suspended in sterile phosphate-buffered salt solutions with a pH and concentration similar to the fluid that surrounds the cells in the human body. Other ingredients of the buffer solution may include gelatin, arginine, sucrose and monosodium glutamate. Gelatin from pigs is used as a stabilizer. Arginine is an amino acid component of protein. Sucrose is common table sugar. Many people are familiar with monosodium glutamate as a flavor enhancer used in foods. In Flu Mist, it also functions as a preservative.
Preservatives
According to the FDA web site, all 2009 FDA-approved multidose influenza vaccines for seasonal and H1N1 contain thimerisol. Thimerisol is a mercury-containing compound used a preservative. Each 0.5 milliliter dose from a multi-dose formulation of influenza vaccine provides about 25 micrograms (0.000025 grams) of mercury as thimerisol. Single dose formulations of influenza vaccine do not usually contain thimerisol. The manufacturer's product insert will always confirm the presence and quantity of mercury for a specific product.
