Vaccination and Immunity

An antigen is any substance (typically a protein or polysaccharide) that the immune system recognizes as foreign and that triggers an immune response, specifically stimulating B cells to produce antibodies. Antigens are usually found on the surface of pathogens like bacteria and viruses. They are not 'opposite' to antibodies but rather stimulate antibody production.

Diabetes is the disease for which no microbe is responsible but is caused due to the improper functioning of a particular body organ. Therefore, it can't be cured by vaccine. 

Antibiotics are the substances that destroy or inhibit the growth of harmful microorganisms, whereas, pathogen refers to a disease causing organism. Vaccine refers to a biological preparation, which is made from modified viruses or bacteria to induce immunity in human beings, and antibodies are present in the blood and helps fighting against infections. 

Vaccines work against infectious diseases caused by pathogens like viruses and bacteria. Smallpox, diphtheria, and tuberculosis are infectious diseases for which vaccines exist (smallpox has even been eradicated through vaccination). Diabetes is a chronic metabolic disorder not caused by a pathogen, so it cannot be prevented or cured by any vaccine.

Vaccines work by introducing weakened or dead forms of pathogens (or their components) into the body. This stimulates the immune system to produce antibodies and memory cells without causing actual disease. When the real pathogen attacks later, the body is prepared to fight it off. Vaccines do not contain antibiotics, antibodies, or living healthy microbes.

BCG vaccine gives immunity against the tuberculosis bacterium. 

This option is correct because DPT vaccine is used as a control measure for diphtheria, pertusis (whooping cough) and tetanus (lockjaw).

Antibodies are Y-shaped protein molecules produced by plasma cells that specifically bind to and neutralize foreign antigens. While they can immobilize bacteria and kill viruses, these are specific functions, not the complete definition. The key characteristic is that they are proteins that inactivate any foreign antigen they encounter.

Smallpox is the only human disease to have been completely eradicated worldwide through a global vaccination campaign led by the WHO, with the last natural case occurring in 1977. Polio is nearly eradicated but still exists in a few countries. Rabies and AIDS are still prevalent globally and have no effective vaccines for prevention.

BCG (Bacillus Calmette-Guerin) vaccine is the first vaccine given to a newborn, usually within the first few hours after birth. It protects against tuberculosis. Rabies vaccine is given after dog bites, DPT is given at 6, 10, 14 weeks, and Tetanus vaccine is given after injuries or as part of DPT.

The DPT vaccine (also called DTP) protects against three bacterial diseases: Diphtheria (Corynebacterium diphtheriae), Pertussis or whooping cough (Bordetella pertussis), and Tetanus (Clostridium tetani). All three causative organisms are bacteria that produce toxins affecting the respiratory system or nervous system. DPT does not target viruses (like polio or measles in other vaccines), fungi, or protozoa.

The second time, our immune system has memory cells which quickly identify the problem and counter it and thus, eliminate it. This is called immunisation. Immunisation is a method of prevention of disease or infection and it also helps to avoid the spreading of a disease.

AIDS is a viral disease caused by HIV. The human body cannot develop immunity against it. The antibodies that human immune system makes to fight HIV are not effective. HIV actually targets, invades and then destroys some of the most important cells in the immune system itself. So, no vaccine is effective in preventing AIDS.  

Edward Jenner created the vaccine for smallpox two centuries ago.

An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes. This recruitment process is called inflammation.