What best describes an inactivated vaccine?

An inactivated vaccine is best described as one that contains chemicals to kill organisms while preserving the integrity of the antigens. This structure ensures that the vaccine can stimulate an immune response without the risk of causing disease, as the pathogens are no longer live. By inactivating the organisms through chemical means, the vaccine maintains enough antigenic structure to educate the immune system about the pathogen, allowing it to recognize and respond effectively if exposed to the live pathogen in the future.

This distinction is crucial because it highlights the safety profile of inactivated vaccines, particularly in vulnerable populations of animals. The other options do not accurately reflect the nature of inactivated vaccines; for instance, they do not contain live pathogens, nor do they present a risk of disease in susceptible animals, and they are indeed effective against various infections, including those caused by viruses.