Question: What are vaccines made of??

Helen Fletcher answered on 17 Jun 2011:

Hi strawberrygirl. I like this question, it’s one of the things I lecture on! Our vaccine is a genetically modified virus. It’s actually a pox virus which has had about on third of its genes deleted so it can’t infect humans any more. We then add in some genes from M. tuberculosis (the bacteria that causes TB). When we give the vaccine it infects human cells, expresses the TB genes as proteins, then dies. So we are using the viral particles as miniature machines to deliver the TB proteins into cells. Clever!! Most other vaccines are more simple. Heat killed or irradiated bacteria for example. Or single proteins from bacteria or viruses and are mixed with a chemical carrier called an “adjuvent”. Proteins on their own can’t induce an immune response which is why they need to be mixed with an adjuvent. If you use a virus to deliver the protein (like we have) you don’t need to use an adjuvent!!