Question

How effective are vaccines?

Answer 1

Vaccine are very effective on stable viruses , but are of limited use in treating a patient who has already been infected.

Explanation:

Researchers working on rational drug design strategies for developing antivirals have tried to attack viruses at every stage of their life cycle.

Designing safe and effectiv antiviral drugs is difficult , because viruses use the hosts cells to replicate. This makes it difficult to find targets for the drugs that would interfere with the virus without harming the host organisms cells.

The major difficulty in developing vaccines and antiviral drugs is due to viral variations.

Several factors including cost , vaccination stigma and acquired resistance limit the effectiveness of antiviral therapies.