Some of the ingredients in a flu shot can appear daunting, but seasonal flu kills 291,000 to 646,000 people worldwide each year. So people have to weigh up the risk versus reward.
When you get a flu vaccine, you have two options: Inactivated influenza vaccines that contain flu viruses that have been killed, so they can’t cause the flu. Live influenza vaccine (LAIV or FluMist) nasal sprays that contain a live but weakened form of the virus.
Here are some ingredients you’ll find in the flu shot: Egg protein Many flu vaccines are made by growing the viruses inside fertilized chicken eggs. This means that they contain a small amount of egg protein. A newer version of the vaccine, called Flucelvax, is grown in animal cells instead. Preservatives Vaccine manufacturers add the preservative thimerosal to multidose vaccine vials. Thimerosal helps prevent and kill dangerous bacteria and fungi in the vial. Thimerosal contains mercury, which can be toxic in large doses. There isn’t enough evidence to show the small amount contained in the flu vaccine is dangerous. But if you’re concerned, thimerosal-free versions of the flu vaccine are available. Stabilizers Sucrose, sorbitol, and monosodium glutamate (MSG) are used to keep vaccines stable. They prevent vaccines from losing potency, even when exposed to heat and light. Sucrose is the same table sugar you spoon into your coffee. Sorbitol is an artificial sweetener that’s also found in chewing gum. MSG is a flavor enhancer. Commonly thought of as an additive in Chinese food, it’s used in many processed foods. Though certain people are sensitive to MSG, the amount found in the flu vaccine is very small. Antibiotics Neomycin, gentamicin, and other antibiotics are added to vaccines in very small amounts. They stop bacteria from contaminating the vaccine. Polysorbate 80 This emulsifier prevents sauces and salad dressings from separating. In vaccines, polysorbate 80 keeps all the ingredients evenly distributed. Though large doses can cause some people to have reactions, the amount in the flu vaccine is very small. Formaldehyde This natural compound is found in household products from glues and other adhesives to pressed-wood furniture. Formaldehyde is a gas that’s soluble in water. It’s used in the flu vaccine to inactivate influenza virus. Routine exposure to large doses of formaldehyde is linked to eye and throat irritation, breathing trouble, and a higher risk for certain cancers. However, according to the Centers for Disease Control and Prevention (CDC), most formaldehyde used in producing a vaccine undergoes removal from the vaccine solution before being packaged and sent to doctors and pharmacies. Per the Food and Drug Administration (FDA), the level of formaldehyde that remains in a vaccine (such as the flu vaccine) is much lower than the amount that occurs naturally in the human body. The residual amount of formaldehyde used in vaccines “does not pose a safety concern,” and “there is no evidence linking cancer to infrequent exposure to tiny amounts of formaldehyde via injection as occurs with vaccines.”
