The flu is a contagious respiratory infection that can produce anything from a mild illness to death. Getting the flu shot can reduce your risk of getting the flu by 70 to 90 percent. However, the vaccine is not for everyone, especially people with a history of certain kinds of allergies. Knowing the ingredients of the flu shot can help you and your doctor decide whether vaccination is right for you.
Virus
The seasonal flu shot 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 Food and Drug Administration also approved a "monovalent," or single strain, vaccine designed exclusively to combat the pandemic H1N1 strain.
Growth Medium
Fertilized chicken eggs are used as the growth medium for influenza virus, and trace amounts of egg white protein (ovalbumin) are reported in each of the 2009-2010 vaccines. All but two manufacturers (Sanofi Pasteur and ID Biomedical) used antibiotics to prevent bacterial contamination of the chicken eggs. The specific antibiotics used include kanamicin, gentamicin, neomycin and polymixin B. People with egg and antibiotic allergies should read the manufacturer's product literature prior to receiving a flu shot.
Detergents
Once the virus has been allowed to replicate in chicken eggs, it must be recovered. This step involves the addition of chemical detergents. 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 type and maximum concentration of the chemicals used in its brand.
Inactivating Agents
According to the Centers for Disease Control and Prevention, the viruses in the flu shot are "inactivated," which means that they are no longer capable of causing infection. Technically, viruses are never alive, so they cannot be "killed" as bacteria are. Vaccines approved for the 2009-2010 flu season used beta-propionolactone or formaldehyde derivatives to inactivate the virus. Each manufacturer's product literature specifies the exact agent used and the maximum concentration present in the final dose.
Buffer Solution
According to the FDA and 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 and sucrose. Gelatin from pigs is used as a stabilizer. Arginine is an amino acid component of protein. Sucrose is common table sugar.
Preservatives
All FDA-approved multi-dose vials of seasonal and H1N1 vaccine contain thimerisol, a mercury-containing compound used a preservative. A flu shot dispensed from a multi-dose vial contains about 25 micrograms (0.000025 g) of mercury as thimerisol. The manufacturer's product insert will always confirm the presence and quantity of mercury for a specific product.
