Vaccine for active immunisation. Subunit and split vaccines do not contain killed complete pathogens, but only biomolecules derived or genetically engineered from them. Most influenza vacc ines are split vaccines made from true influenza viruses.
Several subunit vaccines also contain selected molecules of a pathogen. However, these are not derived from the pathogen itself, but are genetically engineered using yeast, mammalian or insect cells. The necessary genes of the pathogen were transferred to the cells beforehand. Such methods are used, for example, for vaccines against hepatitis B or cholera.