<unk> s contain fragments of the pathogen, such as protein or polysaccharide, whose combinations are carefully selected to induce a strong and effective immune response. Because the immune system interacts with the pathogen in a limited way, the risk of side effects is minimal. An effective<unk>  would elicit the immune response to the antigens and form immunological memory that allows quick recognition of the pathogens and quick response to future infections. A drawback is that the specific antigens used in a<unk>  may lack pathogen-associated molecular patterns which are common to a class of pathogen. These molecular structures may be used by immune cells for danger recognition, so without them, the immune response may be weaker. Another drawback is that the antigens do not infect cells, so the immune response to the<unk> s may only be antibody-mediated, not cell-mediated, and as a result, is weaker than those elicited by other types of<unk> s. To increase immune response, adjuvants may be used with the<unk> s, or booster doses may be required.
Subunit vaccine
Conjugate vaccine
Synthetic vaccine
Attenuated vaccine
Inactivated vaccine
Heterologous vaccine
Cell-based vaccine
Genetically modified vaccine