Many people will be familiar with the concept that a vaccine against a particular virus will contain a small amount of the pathogen or a part of it, at least.

When we receive the vaccine, the viral interloper triggers our immune system to launch a series of events that leave us protected against the pathogen in the future.

But a glance at the ingredients in common vaccines reveals a long list of other components, the roles of which might not seem so clear cut.

What is the purpose of the likes of gelatin, thimerosal, and Polysorbate 80? And why do some vaccines contain aluminum?

In this Special Feature article, we look at the active and inactive ingredients that make their way into vaccines and reveal what their role is in protecting us from infectious diseases.