vaccination

[ashee805]

the world health organization has announced the complete eradication of smallpox and is now working toward the eradication of measles and polio. why would vaccination be more likely to eradicaiton a viral disease than a bacterial disease?

[biostudent84]

Vaccination is the imjection of a weaker form or a disabled form of a pathogen. Take a look at the difference between a bacteria and virus. A bacteria is a living organism that can adapt to many enviornments. It would be very difficult to make a vaccination for a bacteria (difficult, but not impossible).

A virus, on the other hand is not an organism (some argue that a virus is a living organism...I can argue that elsewhere if anyone wants). It is simply a piece of RNA surrounded by a protein coat. It is very simple to alter a virus just a little bit so that you have a primary immune response to it without getting sick. If you have a primary immune response to something, in the future, if you are exposed to the EXACT same pathogen, the secondary immune response destroys the pathogen before it makes you sick.

[2810712]

. A bacteria is a living organism that can adapt to many enviornments. It would be very difficult to make a vaccination for a bacteria (difficult, but not impossible).
Why difficult? The until the genes of a specefic surface Ag remain intact in the genome
our vaccine wud work, and the chance of change in the genes is directly proportional to how many times the bacteria hve reproduced .
Same is the case is with viruses , i.e. the chances of change in surface Ags is directly proportional to how many times viruses hve reproduced . As per I know the viruses reproduces much faster than bacteria , so, why would vaccination be more likely to eradicaiton a viral disease than a bacterial disease? How can we say that it is difficult to produce a vaccine for bacteria than viruses? help...........

hrushikesh

[thank.darwin]

the world health organization has announced the complete eradication of smallpox and is now working toward the eradication of measles and polio. why would vaccination be more likely to eradicaiton a viral disease than a bacterial disease?

Smallpox was eradicted a while ago and the last time it was brought back was around 9/11 - I don't know if it has been experimented with sence then. So for right now it is just sleeping in a freezer down in the CDC's headquarters- it is "the demon in the freezer" if you will, and it was eradicated through ring vaccination.

[canalon]

Hi,

Another reason for the possibility of eradication of smallpox, polio and measles is the host specificity of the virus. Since human beings are the only reservoir, the vaccination of humans is sufficient to oeradicate the virus.
But for most of the diseases, human is just an opportunistic host for the virus, and siince it is impossible to vaccinate the normal host, eradication is impossible.

But, as HIV, a human specific virus, demonstrate, the viral capacity for adaptation is also critical to build a good vaccine. High muttaion rates of the viral target make the design of a vaccine highly difficult.

Hope this helps

[thank.darwin]

But, as HIV, a human specific virus

Correct me if I'm wrong but HIV isn't just a human specific virus - It originated in other animals before it crossed over to humans.

[canalon]

Correct me if I'm wrong but HIV isn't just a human specific virus - It originated in other animals before it crossed over to humans.

Hmmm... It has certainly evolved from a non human specific virus, but it seems that in its form, contamination occur only between human beings. Making the human beings the only significant reservoir of the infection.
Not like the flu viruses that exist in animals, and regularly contaminate humans from those, hence making the vaccination (and effective vaccines exist...) useless to eradicate flu pandemics each year. The animal reservoir allowing recombinations between strains, hence the new pandemic each year, and the need of a new vaccine.

[thank.darwin]

Thank you for clearing that up for me.

[Dr.Doom]

the rate of mutation is not directly proportional to the number of replication because mutation is a totally random event. It may seem that way but its not; so there is no direct proportion (you cannot calculate the amount of mutation directly given the rounds of replication); and HIV, i think, came from monkey like animals.

[canalon]

the rate of mutation is not directly proportional to the number of replication because mutation is a totally random event. It may seem that way but its not; so there is no direct proportion (you cannot calculate the amount of mutation directly given the rounds of replication); .

Yes? what's your point here?

and HIV, i think, came from monkey like animals

Isn't it what I said? HIV probably comes from animal, and yes monkeys are the most probbale candidate, even if as far as I know, we still don't know where HIV originated.
But know the main strains of HIV have no significant animal reservoir. It is probably safe to assume that a virus crossed the species barrier and contaminated some humans and evolved in the virus we now know inside humans. If we could get rid of HIV through vaccination in humans, there would probably be no reservoir for the virus to hide and to develop to overcome the vaccination.