why is making anti-viral drugs more difficult than making anti-bacterial medicines?
Viruses have different forms and they can only grow, divide and live inside the body of a host. They cannot survive without a host. Thus it is difficult to culture virus outside host’s body or in a lab. If possible, the expense will be very high. More over viruses are mutating continuously, so the vaccines which act once successfully may not be effective next time. For all these reasons it is difficult to develop vaccines for viral diseases.