What’s Really in a Flu Shot?

What’s Really in a Flu Shot?



As a pharmacist, I often answer questions about flu shots. Should I get a flu shot? Yes! Can you get the flu from a flu shot? No! What’s really in there?  Only essential ingredients, including:

Four inactivated flu viruses:

Each year, flu strains in the vaccine are selected based on the most commonly circulating flu viruses. The viruses are inactivated, or “killed” meaning they cannot replicate or cause a disease.


Ingredients called adjuvants are added to vaccines to create a stronger immune response and help the vaccine work better. MF59 adjuvant is an oil-in-water emulsion with an excellent safety record that is included in some flu vaccines.  


To supply enough flu vaccine for the entire country, some vaccine is stored in multi-dose vials. To prevent contamination and unwanted microbial growth, preservatives are included. The most controversial preservative is thimerosal, a compound containing mercury. Reputable scientific studies have shown that mercury in vaccines is not a cause of autism. Thimerosal is not present in individual-dose flu vaccines.  


Sugar or gelatin keep the vaccine effective after manufacture

Residual materials:

Some ingredients are used to manufacture the vaccine, but not needed for it to work. Despite removal after production, some trace amounts remain in the vaccine, including:

  • Antibiotics that prevent bacterial growth during manufacturing
  • Inactive ingredients like formaldehyde used during manufacturing to “kill” the virus so it won’t cause disease
  • Egg protein used to grow the virus

By combining these ingredients, flu vaccines are made each year, according to the strains selected by the World Health Organization. The Centers for Disease Control and Prevention, or CDC, is the authority on vaccines and expresses no preference for one flu vaccine over another.  

Experts across many fields of study agree that everyone six months and older should receive an annual flu vaccine. Flu vaccines have been shown to reduce the risk of illness, hospitalizations and flu-related death in children. If you expect to travel internationally in the next year, routine vaccines like the flu shot are often on the list of vaccines recommended or required. Protecting yourself, your loved ones, and those who cannot be vaccinated is top priority this season. Your pharmacist or other healthcare provider can provide routine and other travel vaccines you may need, including the flu shot!  

Disclaimer: This information is educational only and not providing healthcare recommendations. Please see a healthcare provider.


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