Economic changes have helped to change the population structure of India.
In 1985, India had a typical population structure of a developing country with large numbers of young children and a rapidly decreasing number of older people. This was caused by:
- A high birth rate since having a large number of children was seen as an asset - they could help work on the farm and look after their parents in their old age.
- Life expectancy of older people was low due to the lack of good medical care and poor access to clean water.
Although there is a large number of children under 15, this is no longer increasing and there is a sign of a decline in the number of very young children 0-5 years old. This is caused by:
- A decline in birth rates. As more people work in secondary and tertiary jobs, children are seen as less of an asset and so the birth rate has dropped.
- The development of the economy has improved the education of the population and so more people are pursuing a career before having children, resulting in smaller families.
- The life expectancy of older people has increased due to improvements in medical care, particularly in the use of vaccinations and improved sanitation, reducing the number of deaths due to water-borne diseases.
Vaccination involves exposing the body’s immune system to a weakened or harmless version of the pathogen in order to stimulate white blood cells to produce antibodies. Antibiotics are used to treat bacterial infections. Bacteria can mutate and become resistant to antibiotics. This is one reason why new drugs are constantly being developed.
People can be immunised against a pathogen [pathogens: microorganisms that cause disease ] through vaccination. Different vaccines are needed for different pathogens.
Vaccination involves putting a small amount of an inactive form of a pathogen into the body. Vaccines can contain:
- live pathogens treated to make them harmless
- harmless fragments of the pathogen
- toxins [toxins: a type of natural poison produced by an organism, often as a form of protection ] produced by pathogens
- dead pathogens.
These all act as antigens [antigens: Foreign organisms that get into the body, and trigger an immune response. ]. When injected into the body, they stimulate white blood cells to produce antibodies to fight the pathogen.
The vaccine contains only a weakened or harmless version of a pathogen, which means that the vaccinated person is in no danger of developing the disease. Some people, however, may suffer a mild reaction. If the person later becomes infected with the pathogen, the required (white blood cells) are able to reproduce rapidly and destroy it.
Vaccines and boosters
Vaccinations in early childhood can offer protection against many serious diseases. Sometimes more than one vaccine is given at a time, like the MMR triple vaccine against mumps, measles and rubella.
Sometimes vaccine boosters are required because the immune response ‘memory’ weakens over time. Anti-tetanus injections may need to be repeated every ten years, for example.
Ideas about science - making decisions
There is often a conflict between a person’s right to decide what is best for themselves and their family and what is best for society as a whole. For example, some people used to think the MMR (measles, mumps or rubella) vaccine could cause autism in children. They decided not to risk letting their child have the vaccine and hoped they would not catch any of the three diseases. But this meant that as less and less children were vaccinated the diseases began to spread more easily and the number of cases began to increase. Therefore, a decision originally taken by a number of single individuals had big implications for society as a whole.
Vaccinations can never be completely safe because side-effect levels vary. So, when making a decision, these are some of the factors that should be considered:
- when fewer people are vaccinated, the number of cases of the disease increases
- the chance of falling seriously ill or dying from the disease may be far greater than the chance of experiencing a serious side-effect
- using a vaccine may be much cheaper than treating a very ill person.
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