Introduction:
Vaccines produced through genetic engineering are considered safe because they contain only the coat of the pathogen, also known as the antigen. This means that they do not contain the entire pathogen or its genes, reducing the risk of causing disease.

Explanation:
When developing vaccines through genetic engineering, scientists isolate the specific antigen that triggers an immune response against the pathogen. This antigen is then inserted into another organism, such as yeast or bacteria, which acts as a host to produce large quantities of the antigen.

The coat of the pathogen:
The coat of the pathogen, or antigen, is the part of the pathogen that is recognized by the immune system and stimulates the production of antibodies. By using only the coat of the pathogen, vaccines produced through genetic engineering are able to stimulate an immune response without causing the actual disease. This greatly reduces the risk of adverse effects and ensures the safety of the vaccine.

Attenuated form of a pathogen:
Option B states that the vaccines produced through genetic engineering are attenuated forms of the pathogen. While attenuated vaccines can be produced through genetic engineering, this is not always the case. Attenuated vaccines are created by weakening the pathogen so that it can still stimulate an immune response but does not cause disease. This is achieved through a variety of methods, such as growing the pathogen under specific conditions or modifying its genes. Attenuated vaccines do contain the entire pathogen, unlike the vaccines produced through genetic engineering which only contain the coat of the pathogen.

Killed form of pathogens:
Option C suggests that the vaccines produced through genetic engineering have the killed form of pathogens. Killed vaccines are created by inactivating the pathogens using methods such as heat or chemicals. However, vaccines produced through genetic engineering do not necessarily use the killed form of pathogens. Instead, they use only the coat of the pathogen, as explained earlier.

All the genes of pathogens:
Option D states that the vaccines produced through genetic engineering have all the genes of the pathogens. However, this is not the case. Vaccines produced through genetic engineering only contain the specific genes necessary to produce the antigen or coat of the pathogen. These genes are inserted into another organism, which then produces the antigen. The vaccine does not contain all the genes of the pathogen, reducing the risk of adverse effects.

Conclusion:
Vaccines produced through genetic engineering are considered safe because they contain only the coat of the pathogen, also known as the antigen. This means that they do not contain the entire pathogen or its genes, reducing the risk of causing disease. By using the coat of the pathogen, these vaccines can stimulate an immune response without causing the actual disease, ensuring their safety and effectiveness.