Expand DPT and BCG.

Hint: Vaccines are biological products prepared to improve immunity against a particular infectious disease. It builds the body's natural immunity. They act as a defense mechanism for our body and are one of the safest medical measures.

Complete answer:
We require vaccines to protect ourselves from a dangerous, contagious disease that is constantly present in a population or region (i.e. endemic). Vaccines contain a weakened or dead form or surface proteins or toxins of the agent that resembles the disease-causing microorganisms. These vaccines are given in the form of injections or by mouth containing a dead or weakened form of microbes and this process is known as vaccination.

DPT- It is a combination of vaccines against three infectious diseases in humans: Diphtheria, pertussis (or whooping cough), and tetanus. Components of this vaccine include toxoid of diphtheria and tetanus while killing whole cells of the bacterium that causes pertussis or its antigen. It provokes immunity against disease diphtheria, tetanus, and whooping cough or pertussis which is a respiratory disease of humans. It is used for immunization of children up to the age of 7 and is given in five shots at 2,4,6,18 months and 4 to 7 years of age.

BCG- It is Bacillus Calmette-Guerin (BCG). It is a vaccine against Tuberculosis disease. One of the most widely used vaccines amongst all other vaccines. It provokes immunity against human tuberculosis (TB) which is a bacterial disease caused by the bacteria Mycobacterium tuberculosis, which primarily attacks the lungs but also attacks the other sites such as the spine, kidney as well as brain. BCG vaccination leaves the scar at the site of injection. Vaccination can be given at any time up to the age of five but best suited up to six months.

Note: Vaccines are cost-effective. It is used to boost the body’s immunity and prevent serious diseases. They can be prepared against various microbes like - viruses, bacteria, etc and first human vaccines were the smallpox vaccine.