Question

.What is Vaccine? Discuss the four major ways in which vaccines can be made to fight a virus or bacterium and describe how each vaccine works

Answer 1

ANS:

A vaccine is defined as a type of medicine that trains the body’s immune system to fight a disease it has not come into contact with before. Vaccines are designed specially to prevent diseases, rather than treating a disease once you have caught it.

Vaccines are made by taking viruses or bacteria and weakening them so that they can't replicate themselves. Four ways in which vaccines can be made to fight a virus or bacterium are:

• Change the virus blueprint: It is done so that the virus replicates poorly. This is how the measles, mumps, rubella etc. vaccines are made. The blueprint of the virus is changed by a technique called cell culture adaptation. Since viruses can still, upto some extent, can make copies of themselves after cell culture adaptation therefore they are often referred to as live, attenuated or weakened viruses.

• Destroy the virus blueprint: It is done so that the virus can’t replicate at all. This is how the “killed” polio vaccine is made. Vaccine virus is made by treating polio virus with the chemical formaldehyde and this treatment permanently destroys the genes of the polio so that the virus can no longer replicate itself.

• Use only a part of the virus or bacteria. This method is used to make the vaccines for Hib, hepatitis B, and (in part) pertussis. Since the viral or bacterial genes are not present in the vaccine, therefore the viruses or bacteria can’t replicate.

• Take the toxins which are released from the bacteria, purify them, and kill them: Some of the bacterias cause diseases not just by replicating but by manufacturing harmful proteins called toxins. For example, bacteria like diphtheria, tetanus, and pertussis (whooping cough) all cause disease by producing toxins. To make vaccines against these bacteria, toxins are purified and killed with chemicals (such as formaldehyde). Again, because bacterial genes are not part of the vaccine, bacteria can’t replicate.