Fluzone (Regular and High Dose)

This is a quadrivalent flu vaccine

For a more detailed explanation of some of the ingredients, see this article: https://www.wired.com/2014/11/whats-inside-flu-shot/


Active ingredients:

Inactive influenza virus from 4 serotypes

  • H1N1

  • H3N2

  • Victoria lineage

  • Yamagata lineage

There is a high-dose version of Fluzone for people 65 and older. The ingredients themselves are exactly the same, but there is a higher amount of both the active and inactive ingredients. Differences in the amount of each inactive ingredient are indicated below.

Inactive ingredients:

Buffers: A mixture that resists pH changes.

Preservatives: prevent bacterial growth and contamination

*Thimerosal is only in multi-dose vials of flu vaccines, which means that one vial of vaccine contains multiple doses. As a result, the container would be reused, so it needs a preservative to prevent contamination between the different uses from the same vial.


Relevant Terms

  • pH: a measure of how acidic or basic a solution is. The scale ranges from 0 (very acidic) to 14 (very basic). A pH of 7 is neutral.

  • Quadrivalent: Protects against four different versions of the pathogen (in this case, influenza virus)

  • Serotype: a group of strains within a species that share a particular type of surface structure.

  • Surfactant: a substance like a detergent. They are used in vaccines because they are able to disrupt the membrane (outer layer) of a virus and inactivate it.