Vaccination and Immunity

This is the correct chronological sequence. In 1936, J. D. Bernal, F. C. Bauden, N. W. Pirie isolated ribonucleic acids from TMV. In 1938, Max Theiler's vaccine against yellow fever was proved successful in field trials. In 1939, E. L. Ellis and Max Delbruck established the concept of one-step viral growth cycle for a bacteriophage active against E. coli and in 1940, Helmuth Ruska used an electron microscope to obtain the first pictures of a virus.

Heat labile toxin (HLT) causes damage to epithelium of the respiratory tract.

Subunit vaccines are a development of the killed vaccine approach. Examples are: Hepatitis B vaccine (HBV), Pertussis (part of DTaP combined immunisation) vaccine, Pneumococcal vaccine, Meningococcal vaccine, etc.

In herd immunity, only some of the inhabitants are immunised and others develop immunity themselves. It is a form of indirect protection from infectious diseases that occurs when a large percentage of population has become immune to an infection. It provides a measure of protection for individuals who are not immune.

Smallpox vaccine, the first successful vaccine to be developed, was introduced by Edward Jenner.

Deaths due to malnutrition and infections occur in post-neonates, if immunisation is not done in them.

The Pulse Polio Immunization program was launched in India in 1995-96 to eradicate polio through nationwide immunization days. Leprosy elimination programs were from earlier decades, smallpox was eradicated by 1977, and ORT popularization predates 1996.

The correct matching is: BCG Vaccine - Tuberculosis (III-A), BPL Vaccine - Rabies (IV-B), Chloroquin - Malaria (I-C), Penicillin - Sore throat (II-D, though penicillin treats bacterial infections broadly). This gives III-A, IV-B, I-C, II-D.

It is an infectious disease of dogs, cats, and other animals, transmitted to humans by the bite of an infected animal.

Prophylactic measures prevent disease by blocking pathogen contact, unlike chemotherapy (treating existing disease), immunization (building immunity), or therapeutic measures (treating after infection). Prophylaxis is prevention-focused.

DPT vaccine is used as control measure for diphtheria, pertusis (whooping cough) and tetanus (lockjaw).

DPT contains whole-cell pertussis vaccine which can cause fever and lower the seizure threshold. In children with convulsion disorders, DT (without pertussis) or DTaP (acellular) is preferred to avoid precipitating seizures.

An 18-month old child has received only one dose each of OPV and DPT (should have completed primary series of 3 doses by 6 months). Standard practice is to complete the vaccination schedule according to age, not restart from scratch. Option B correctly identifies giving BCG (if not given at birth), Measles vaccine (due at 9 months), and booster doses of OPV/DPT to complete protection. Option A incorrectly suggests restarting the entire schedule rather than completing it.