
Problems with Vaccines
Problems with Vaccines
Not all vaccination programs are completely successful in eradicating a disease. One that was, is the smallpox vaccine.
This disease was caused by the variola virus. 12-30% of sufferers died while many who recovered were often blinded. In 1967, WHO (the World Health Organisation) vaccinated more than 80% of the worlds population who were at risk and when a case was reported all possible contacts in the area were vaccinated (ring vaccination).
Eradication in rural areas proved a challenge, but the last case occurred in Somalia in 1977 and in 1980, WHO declared the world free of smallpox.
Reasons for the success of the vaccine included:
- The variola virus did not mutate and change its antigens.
- It was made from a live harmless strain of a similar virus, so it mimicked a natural infection, multiplying and continually presenting the immune system with a large dose of antigens.
- It could be freeze-dried and kept for six months aiding distribution.
- Infected people were easy to identify.
- It was easy to administer and the disease did not linger in the body.
- Smallpox does not infect animals.
Less successful vaccination programs have included those against measles, tuberculosis, malaria and cholera.

This disease offers the promise of eradication if worldwide surveillance was followed-up by vaccination.
However, so far it has failed because:
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A poor response to the vaccine has been shown by some children, who need boosters.
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High birth rates and shifting populations make following-up cases difficult.
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Migrants and refugees may spread the disease.
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Measles is highly infective and 95% immunity of a population is required to prevent transmission.
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The vaccine only has a 95% success rate.

This disease was once thought to have been eradicated, but is actually showing a resurgence.
The reasons include:
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Some TB bacteria are resistant to drugs used to treat them because they can mutate.
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AIDS can allow TB to infect an individual due to their compromised immune system.
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Poor housing and homelessness lowers peoples' natural resistance.
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There have been breakdowns in the TB control program.
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It is actually caused by two different bacteria with two different antigens, which can live inside human cells, making them hard to fight.
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It can be carried in cattle.

This is a disease caused by Plasmodium, a protoctist (eukaryotic) that has hundreds or even thousands of different antigens. It also has three different stages in its life cycle, meaning that developing a vaccine is incredibly challenging and has not yet been achieved.

This disease is caused by Vibrio cholerae, which can live in the intestines where antibodies - produced by vaccines that are injected - cannot get to it. An oral vaccine is in development.