HIV has a very high mutation rate, a rapid reproductive rate, and an enormous population size. This means that at any given time, a human infected with HIV is carrying tens of millions of HIV virions with millions of different random mutations. Inevitably, sooner or later, a mutation will occur that confers resistance to AZT. (This will typically be a mutation that causes greater selectivity in the active site of the reverse transcriptase enzyme.) Notice that the HIV population has heritable variation for resistance to AZT before exposure to AZT. However, at this stage the resistance to AZT occurs only in one or a few virions, out of the billions.
Step two is for the patient to begin taking AZT. This prevents or slows replication of most HIV virions, and those strains die out. But the lucky virion with the right mutation will survive and will be able to replicate.
The surviving HIV virions then repopulate the host. Soon the entire HIV population is composed of resistant virions.
It has a high mutation rate causing different strains.
It is difficult to develop a vaccine because the virus changes (mutates) very quickly. Thus scientists do not have a stable target to make the vaccine against.
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.
Part of the problem in developing an effective vaccine so far has been the issue of mutation. The HIV virus mutates, or changes, rapidly. What this means for vaccine research and development is that as we are studying the virus and figuring out what will be effective against it, it changes, making whatever we have so far come up with ineffective.
because there are different number of species with different effects that they can cause, therefore it is harder to develop a vaccine for it
No, its because they are so adapted and any attempt to vaccinate them just sort of "upgrades them" So they become immune to that certain vaccine
The seasonal flu vaccine may give only partial protection against H1N1. It is very difficult to prove the same.
The smallpox vaccine is an injection to prevent one from contracting smallpox. It has been used to help the body to develop immunity against the disease.
A small amount of an individual virus itself is always necessary to develop a vaccine.
No; the HBV vaccine will not protect against HIV. There is no vaccine for HIV.
Mutation means a change in form. Some viruses mutate very quickly, and that is the reason we have no vaccine for the common cold. It changes too quickly to develop a vaccine. It changes or mutates several times a day and the nature of the virus changes from region to region, usually within a 50 mile radius.
This virus has an unusually high mutation rate causing it to change preventing a vaccine from being developed that will be effective against it for a long enough period of time to produce lasting immunity.
The vaccine was developed in 1885 by Louis Pasteur
Edward Jenner - smallpox vaccine.
Lyme disease vaccine has not been produces since 2003, but once a person is infected with a particular strain of the disease, they can develop an immunity that can last up to nine years.
Because such a wide-spread virus would be constantly mutating.
the h1n1 vaccine does not work all the time
HIV is a very complex, highly changeable virus. Even if it gets killed by the medicines or vaccines, it gets reactivated. Scientists are continuing to make and test HIV vaccines in animals, and even in human subjects.
A vaccine works by producing antibodies to immunize the body against the virus that vaccine is intended to protect against.
Yes. There is a rabies vaccine.
The act or practice of inoculating someone with a vaccine as a protection against disease is known as a vaccination. Examples of vaccinations include the flu vaccine and the MMR vaccine.
Not specifically, but the HBV vaccine will protect against HDV.
The vaccine is used to inmunise your body against specific diseases.