Edward Jenner is widely recognized as the father of immunology. In 1796, he pioneered the concept of vaccination by using cowpox material to provide immunity against smallpox. His work laid the foundation for modern immunization practices, demonstrating that exposure to a milder form of a pathogen could protect individuals from more severe diseases.

The BCG vaccine is a live-attenuated vaccine derived from Mycobacterium bovis. It is primarily used globally to protect against tuberculosis, particularly severe forms in children such as tuberculous meningitis and miliary tuberculosis. While it has been studied for other uses, its clinical indication remains the prevention of tuberculosis.

The smallpox vaccine utilized the vaccinia virus, which is a related but less virulent virus. By introducing these weakened or attenuated germs into the body, the immune system is trained to recognize and fight the pathogen without causing the full-blown disease. This creates immunological memory, providing protection against the more dangerous variola virus responsible for smallpox.

The transition to Bivalent Oral Polio Vaccine (bOPV) was a strategic move by the Government of India to eliminate Type 2 poliovirus, which had been eradicated globally. The bOPV targets only Type 1 and Type 3 polioviruses, reducing the risk of vaccine-derived poliovirus type 2 (VDPV2) while maintaining effective immunity against the remaining circulating strains of the virus.

The DPT vaccine is a combination vaccine that protects against three serious bacterial diseases: Diphtheria (caused by Corynebacterium diphtheriae), Pertussis (whooping cough, caused by Bordetella pertussis), and Tetanus (caused by Clostridium tetani). It is a critical component of childhood immunization schedules globally.

Statement I is correct because active immunity involves the host's immune system actively responding to antigens. Statement II is incorrect because the administration of pre-formed antibodies, such as anti-venom, is a form of passive immunization, where the body does not produce its own antibodies in response to the toxin.

Diabetes, particularly Type 1 and Type 2, is a metabolic disorder related to insulin production or sensitivity, not an infectious disease caused by a pathogen. Therefore, it cannot be prevented by vaccination, unlike polio, whooping cough, and smallpox, which are caused by viruses or bacteria.

The DPT vaccine is a combination vaccine that protects against three infectious diseases: Diphtheria (caused by Corynebacterium diphtheriae), Pertussis (whooping cough, caused by Bordetella pertussis), and Tetanus (caused by Clostridium tetani). It is a critical component of pediatric immunization schedules worldwide to prevent these potentially life-threatening bacterial infections.

The DPT vaccine is designed to immunize individuals against Diphtheria, Pertussis (commonly known as whooping cough), and Tetanus. It is a standard childhood immunization that helps prevent these severe bacterial infections.

The Bacillus Calmette-Guérin (BCG) vaccine is primarily used to provide immunity against tuberculosis (T.B.), caused by Mycobacterium tuberculosis. It is most effective in preventing severe forms of childhood tuberculosis, such as tuberculous meningitis. While it is a standard part of immunization programs in many countries, its efficacy in preventing pulmonary tuberculosis in adults varies significantly depending on geographic and environmental factors.