What’s In Your Jab? The Ingredients In Vaccines

As we move into the flu season, many people will be heading out to get their influenza vaccines. 

In a post and ongoing Covid world where getting regular vaccines is the norm, how much do you actually know about vaccine ingredients? 

When you read the ingredients list of your average flu vaccine, you may notice words like formaldehyde, polysorbate 80, and thimerosal, while there are other interesting ingredients you may not come across, for example, egg protein. 

Many flu vaccines are made by growing the viruses inside fertilised chicken eggs, which means they contain a small amount of egg protein. 

In this episode of The Science Briefing, Dr Sophie Calabretto talks to Cosmos Magazine journalist Ellen Phiddian about exactly what is in your jab and some of the ingredients that may surprise you. 

Phiddian said the most important ingredient in vaccines is an active ingredient that triggers an immune response within our bodies. 

“An active ingredient can also be something called mRNA, which is basically the instructions to make part of the virus. So, the Pfizer and Moderna Covid vaccines both have mRNA in them as active ingredients,” Phiddian said. 

Phiddian said there are other ingredients called excipients, extra substances that assist the active ingredients in stabilising, getting it to the right spot in the body, and helping the vaccine to mix. 

Phiddian also listed a number of ingredients that caught her attention, one of them being alcohol, also recognised as ethanol. 

“The ethanol is identical to the alcohol you get in hand sanitiser, beer, and wine, but the concentration is much much lower. So, we are talking about 0.05% of a half-a-millilitre dose, it’s a very, very small amount. It’s not going to affect you at all,” Phiddian said. 

She explained that ethanol was particularly used as a solvent to help dissolve other ingredients in the vaccine. It could also be used in vaccines that were hard to refrigerate and store. 

Tune into the full episode of Science Explained with host, Dr Sophie Calabretto to hear the full recap of this month’s discoveries. 

Introducing The Science Briefing: a podcast about the science of everything and your new go-to podcast for your snapshot of science news. Hosted by Dr Sophie Calabretto and featuring journalists from Cosmos Magazine.