Simplify the following text for a Grade 12 native English-speaking person.
Original: While most vaccines are created using inactivated or attenuated compounds from micro-organisms , synthetic vaccines are composed mainly or wholly of synthetic peptides , carbohydrates or antigens .
Simplified: While the majority of vaccines are dead , inactivated or attenuated organisms , purified products derived from them , some vaccines are synthetic vaccines . The latter are composed mainly or wholly of synthetic peptides , carbohydrates or antigens .