Seasonal flu and H1N1 (swine flu) vaccines are available in the United States in intramuscular injection ("flu shot") and intranasal (nasal spray) forms. While the exact ingredients will differ slightly depending on the company that manufactured the vaccine and its intended administration (single-dose versus multiple-dose, intranasal versus injection), most flu vaccines contain the same categories of substances.
Eggs and Protein
Flu viruses are prepared in chicken eggs; therefore, the final vaccine can contain trace amounts of egg or egg products. Those who are allergic to eggs are advised not to get the flu vaccine in order to avoid an allergic reaction. Egg albumin or ovalbumin (the major protein of the egg white), and egg protein can be found in regular and H1N1 influenza vaccines. The seasonal FluMist vaccine also contains protein in the form of chick kidney cells.
Sterilizers
Certain chemicals are added to vaccines to sterilize them. Formaldehyde is a chemical widely known for its use in the chemical manufacturing industry that can also be used as a preservative and antibacterial agent. Some flu vaccines are toxoid vaccines that are made from the toxins of a live flu virus. These toxins need to be inactivated so they do not cause harm to the human body, and formaldehyde is used to neutralize the toxins. Formaldehyde is also used to destroy viruses and bacteria that might contaminate the vaccine during production or storage.
Beta-propiolactone is another sterilizing chemical commonly used in regular and H1N1 flu vaccines.
Buffers, Additives and Preservatives
Thimerosal is a preservative that contains mercury that is added to influenza vaccines to prevent the growth of bacteria and other contamination. H1N1 vaccines manufactured for single-dose administration (as opposed to being given in separate, multiple doses) are available without thimerosal. The H1N1 intranasal (nasal spray) vaccine also does not contain thimerosal or other preservatives.
Vaccines are suspended in a saline solution that is typically buffered with phosphates such as sucrose phosphate glutamate buffer. Sodium chloride (table salt), monobasic sodium phosphate, dibasic sodium phosphate, monobasic potassium phosphate, potassium chloride and calcium chloride may also be added.
Stabilizers
Stabilizers are components that are added to flu vaccines to keep them from chemically changing when exposed to heat, light, acidity or humidity. Monosodium glutamate (MSG) is a stabilizer used in the Influenza FluMist and H1N1 intranasal (nasal spray) vaccine. Gelatins may also be used as stabilizers, and can be found in some of the H1N1 and seasonal flu injection vaccines.
Detergents and Emulsifiers
Detergents and emulsifiers are surfactants used to help dissolve oil in water and promote the mixture of two substances that do not ordinarily mix. Sodium taurodeoxychoalate, sodium deoxycholate, polysorbate 80, triton X-100 and nonylphenol ethoxylate are examples of surfactants used in some regular flu and H1N1 injection vaccines.
Antibiotics
Antibiotics are added to flu vaccines to prevent the growth of bacteria during the period the vaccines are being produced and stored. Antibiotics found in influenza vaccines include polymyxin B, gentamicin and gentamicin sulfate, and neomycin. Those who are allergic to any antibiotics should consult their health care provider before getting any flu vaccinations.
