Why is it difficult to develop vaccine against viral disease?

Answer 1

viruses dont have mtabolism.Drugs must stop one of the steps of replication but that ocurre inside the host cell.Viruses mutate faster than bacteria creatin generation that are resistant to antiviraltherapy or difficult to find one.

Answer 2

The virus can live,grow and multiply only inside the body of their specific host because the viruses have only a few biochemical reactions of their own. They cannot be cultured on artificial medium,so it is difficult to develop vaccine against viral diseases.

Answer 3

I think you got this the wrong way round. It is infact harder to develop a drug to destroy a virus than it is to develop a drug to kill bacteria. This is because you can't destroy a virus like bacteria because,

A. it doesn't eat

B. It doesn't need energy

and C. It doesn't reproduce like Bacteria.

Bacteria split and reproduce on their own, where as a virus takes over the patients body and tricks the cell into reproducing a virus. The cell then bursts and releases the new virus etc.

So the only way we could kill the virus (or destroy it) would be by destroying the cells which in turn would lead to the destruction of the patient too.

Hope this helps~

Answer 4

A bacterium is a single-celled organism. It's very small and rather simple as living things go. It contains within itself all the bio-chemical machinery necessary to eat, extract energy from food and reproduce itself. It contains in its DNA a complete blueprint for the manufacture of a copy of itself, and the cell is equipped with all the special chemicals needed to decode the blueprint properly and to make the copy.

A drug that is intended to destroy or at least render harmless a bacterium can be designed to attack almost any of the processes that the organism uses. Any process used by the bacterium that is not used by the human body, or that is used in a radically different way, can be targetted by a drug.

A virus is a quite different thing. It is much smaller than a bacterium. It is not a cell. It has no machinery to eat or reproduce itself. It is little more than naked DNA; about the only part of it that has a function other than to be a blueprint for its copying is a protein that helps it enter a cell.

Once a virus enters a cell it hijacks the reproductive machinery in the cell. A little bit like the cuckoo's egg in the nest, it substitutes its DNA for the DNA in the nucleus of the animal cell, so the cell makes copies of the virus. There is no "enough already" code on the virus DNA, so the cell copies the virus until there is so much of it in the host cell that the cell bursts, and new viruses flood through the body looking for new targets.

The fundamental problem in developing a drug against viruses is this :- you can't attack a virus's metabolic processes because it doesn't have any. You can't attack its reproductive system because it doesn't have any. It uses the machinery of the human cells. Easy to attack these, and kill them, but that kills the patient too.

Answer 5

Viruses are organisms that are quick to mutate. A single flu virus can change. A vaccine developed for one strain is ineffective against a new strain.