A virologist develops a way to weaken a deadly virus and then injects this weakened virus into mice. The mice live. When subsequently exposed to the original deadly virus, none of the mice become sick. Which of the following has the virologist potentially developed?

An anesthetic is a substance used to induce a loss of sensation or consciousness and is not related to the immune response. It does not provide immunity against viruses; rather, it is typically used in medical procedures to alleviate pain. Therefore, this option does not align with the scenario of protecting against viral infection.

Gene therapy involves altering the genes inside an individual's cells to treat or prevent disease. While it is a promising field in medical research, this approach is not applicable in the context of immunization against viral infections. Gene therapy does not involve the use of weakened viruses to stimulate an immune response like a vaccine does.

Antibiotics are designed to combat bacterial infections and are ineffective against viruses. Since the scenario involves a viral infection, this option is irrelevant. Vaccines, rather than antibiotics, are the appropriate tools for preventing viral diseases.