Final answer:
Vaccines can include bacterial proteins and attenuated viruses, but not live pathogenic bacterial cells. Live attenuated vaccines trigger a significant immune response, while subunit vaccines contain only key antigens with a lower risk of side effects.
Step-by-step explanation:
The components of a vaccine can include bacterial proteins, attenuated viruses, but not live, pathogenic bacterial cells. Live attenuated vaccines are developed by weakening the pathogen to establish a subclinical infection that stimulates an adaptive immune response. Similarly, subunit vaccines expose the patient to key antigens of a pathogen without the whole cells or viruses, offering a low-risk profile for side effects. On the other hand, inactivated vaccines contain pathogens that have been killed or rendered inactive, invoking a typically weaker immune response that is often limited to humoral immunity and requiring higher doses and multiple boosters.