Final answer:
Vaccines are made without causing disease by using methods such as killing or denaturing the infectious agent, using its components, or employing genetic engineering. Subunit vaccines are an example of a safer vaccine because they only contain a single antigenic molecule that stimulates the immune system.
Step-by-step explanation:
Vaccines are made so that they do not cause disease by a variety of methods. These methods can include killing the infectious agent with heat, denaturing the infectious agent with chemicals, using a component or protein of the infectious agent instead of the organism itself, genetically engineering the infectious agent to remove the genes that cause disease, or using a related but non-pathogenic strain of an infectious agent.
This process ensures that the resultant vaccine contains elements that stimulate the immune system without causing illness. The inactivated vaccine often contains the whole pathogen cells or viruses that have been killed or inactivated through treatment with heat, radiation, or chemicals.
For example, a hepatitis B vaccine involves inserting a gene encoding a hepatitis B surface protein into yeast. The yeast then produces this protein, which the human immune system recognizes as an antigen.
The presence of this antigenic protein stimulates the immune system to produce antibodies that will protect the patient against the virus if exposed. Such vaccines, known as subunit vaccines, are often safer because they contain only a single antigenic molecule.
Therefore answer is e. all of the above.