Immunisation and Vaccination

Immunisation and Vaccination are important topics in Biology that focus on protecting the human body from infectious diseases. They work by stimulating the immune system to recognize and fight harmful pathogens, ensuring long-term health and prevention of illnesses.

Previous year Questions

Year	Question	Marks
2018	Give a brief account of Acquired Immunity and its types.	5M

Immunity

• Immunity is the body’s ability to protect itself from harmful microorganisms (pathogens), toxins, and other foreign substances. 
• It involves a complex system of cells, tissues, and organs working together to detect and neutralize threats.

Types of Immunity:

1. Innate Immunity (Natural Immunity)

• Definition: The body’s first line of defense against pathogens, present from birth. It provides immediate, nonspecific protection and does not require prior exposure to a pathogen.
• Characteristics:
  • Nonspecific: Same response to all pathogens (bacteria, viruses, fungi, etc.).
  • Immediate Action: Quickly activated upon infection but lacks long-term memory.
  • Broad Range: Responds to general threats, not specific antigens.
  • Limited Duration: Response is short-lived and not pathogen-specific.
• Components:
  • Physical Barriers:
    • Skin: Acts as a mechanical barrier to block pathogens.
    • Mucous Membranes: Trap and expel pathogens in the respiratory, digestive, and urogenital tracts.
    • Cilia: Sweep out trapped microbes in the respiratory tract.
    • Stomach Acid: Destroys ingested pathogens.
• Chemical Barriers:
  • Lysozymes in saliva, tears, and sweat → Break down bacterial cell walls.
  • Defensins → Antimicrobial peptides that disrupt microbial membranes.
• Cellular Defenses:
  • Phagocytes (Macrophages, Neutrophils): Engulf and destroy pathogens via phagocytosis.
  • Natural Killer (NK) Cells: Detect and kill virus-infected or abnormal cells by inducing apoptosis.
• Inflammatory Response:
  • Purpose: Localized response to injury or infection.
  • Process: Release of cytokines (e.g., interleukins) → Attract immune cells → Increased blood flow → Redness, heat, swelling.
• Complement System:
  • A group of plasma proteins that directly destroy pathogens or mark them for phagocytosis.

2. Adaptive Immunity (Acquired Immunity)

• Definition: A highly specific immune response that develops after exposure to a pathogen or its antigens. It is slower to activate but provides long-term protection.
• Characteristics:
  • Specificity: Recognizes and targets specific antigens on pathogens.
  • Memory: Develops immunological memory for faster and stronger responses during subsequent exposures.
  • Diverse Mechanisms: Can respond to a wide variety of pathogens.
  • Delayed Onset: Takes several days to activate after the first exposure.
• ​​Primary and secondary responses are carried out with the help of B-lymphocytes and T-lymphocytes. 
• The function of B lymphocytes is to recognize foreign substances and get attached to them whereas the T lymphocyte’s function is to remember the antigens and also recognize them and respond against them and help B-lymphocytes to produce antibodiesComponents:
  • Humoral Immunity (B Cells):
    • B-lymphocytes produce an army of protein called antibodies each having two light and two heavy chains (immunoglobulins) → Neutralize or opsonize pathogens.
    • Antibody Types:
      • IgG → Provides long-term immunity and crosses the placenta.
      • IgA → Found in mucosal secretions (e.g., saliva, tears).
      • IgM → First antibody produced during infection.
      • IgE → Involved in allergic responses.
      • IgD → Plays a role in B cell activation.
  • Cell-Mediated Immunity (T Cells):
    • Helper T Cells (CD4+): Release cytokines to activate B cells, macrophages, and other T cells.
    • Cytotoxic T Cells (CD8+): Directly kill infected, tumor, or foreign cells by releasing perforins and granzymes.
  • Memory B and T Cells:
    • Immunological Memory: After the first encounter with a pathogen, the immune system creates memory B cells and memory T cells that “remember” the pathogen. If the body is exposed to the same pathogen in the future, these cells trigger a faster and more robust immune response.
    • Function: Basis for vaccines that train the immune system to recognize pathogens.

Comparison Between Innate Immunity and Adaptive Immunity

Feature	Innate Immunity	Adaptive Immunity
Specificity	Nonspecific	Highly specific to antigens
Response Time	Immediate (minutes to hours)	Delayed (days to weeks)
Memory	No memory	Long-term memory (immunological memory)
Components	Physical, chemical barriers, immune cells	B cells, T cells, antibodies
Duration of Protection	Short-lived	Long-lasting protection

Comparison Between B-Lymphocytes and T-Lymphocytes

Aspect	B-lymphocytes	T-lymphocytes.
Origin and maturation	Bone marrow	Bone marrow (for T-cell precursors), thymus (for maturation)
Function	To recognize foreign substances and get attached to them	To remember the antigens and also recognize them and respond against them
Antibodies	Produce army of protein called antibody include IgA, IgM, IgE etc	Help B-lymphocytes to produce antibodies.
Immune response	Show humoral immune response (HI) :  due to presence of antibodies in blood	Show cell mediated immunity (CMI) : Directly attack infected or abnormal cells. The body is able to differentiate ‘self ’ and ‘nonself’ and the cell-mediated immune response isresponsible for the graft rejection.
Type	2 type : Plasma cell and memory cell	3 type: Helper, Killer and Suppressor

Types of Adaptive Immunity

1. Active Immunity:

• Definition: Occurs when the immune system produces its own antibodies and memory cells in response to exposure to an antigen.
• Characteristics:
  • Provides long-term protection with memory cells.
  • Takes time to develop but offers lasting immunity.
• Mechanism: When a pathogen invades the body, the immune system identifies the antigen and activates B and T cells to produce specific antibodies and cytotoxic responses. Memory cells are created for rapid response in the future.
• Types:
  • Natural Active Immunity: Developed after recovering from an infection (e.g., chickenpox).
  • Artificial Active Immunity: Achieved via vaccines (e.g., MMR vaccine).

2. Passive Immunity:

• Definition: Antibodies or immune cells transferred from another person, providing immediate but temporary protection without stimulating the recipient’s immune system.
• Characteristics:
  • It provides temporary immunity since the body does not produce the antibodies itself.
  • Does not create memory cells.
• Mechanism: Antibodies are transferred naturally (e.g., maternal antibodies) or artificially (e.g., immune globulin injections).
• Types:
  • Natural: Maternal Antibodies → Transfer of antibodies from mother to fetus or through breast milk.
  • Artificial: Immune Globulin Injections → Injection of antibodies, like rabies immunoglobulin; Injection of antibodies (e.g., antivenom for snake bites).

Components of the Immune System:

• White Blood Cells (Leukocytes): These are the primary cells involved in immune responses.
  • Phagocytes (e.g., macrophages, neutrophils) engulf and digest pathogens.
  • Lymphocytes (e.g., B cells, T cells) are involved in adaptive immunity.
    • B cells produce antibodies that neutralize pathogens.
    • T cells either help other immune cells or kill infected cells directly.
  • Antibodies: These are proteins produced by B cells.
  • Lymphatic System: Includes lymph nodes, spleen, and lymphatic vessels, which act as filters and centers for immune cells to interact with pathogens.
  • Cytokines: These are signaling molecules that coordinate the immune response, directing immune cells to sites of infection or injury.

Mechanism of Immune Response

1. Recognition:
   • The immune system identifies foreign substances (antigens) as threats.
2. Activation:
   • Innate Immunity: Immediate response using barriers and phagocytes.
   • Adaptive Immunity: Activation of B-cells and T-cells for a specific response.
3. Elimination:Pathogens are neutralized or destroyed through:
   • Antibody mediated Immune Response/ Humoral Immunity (B Cells):
     • Fights extracellular pathogens using antibodies.
     • Antibodies bind to antigens, marking them for destruction.
   • Cell-Mediated Immune Response (T Cells):
     • Fights intracellular pathogens (e.g., viruses). 
     • Killer T cells destroy infected cells.
     • Helper T cells activate other immune cells.
   • Phagocytes engulfing pathogens.
4. Memory Formation:
   • After an infection, memory B-cells and T-cells remain, ensuring a faster response if the pathogen reappears.

Immunisation and Vaccination 

Immunisation

• Immunization is the process of protecting an individual from infectious diseases by stimulating the body’s immune system to recognize and fight specific pathogens (such as bacteria, viruses, or other microorganisms).  
• Immunization can be done in two primary ways: active immunization and passive immunization.

[We have already discussed them, but a brief recap is helpful for revision.]

1. Active Immunization

• Definition: Body creates its own antibodies & memory cells.
• How it works:
  Antigen → B cells make antibodies → T cells destroy infected cells → Memory cells created for future defense.
• Examples:
  • Vaccines (e.g., polio, measles)
  • Natural Infection (e.g., chickenpox)

2. Passive Immunization

• Definition: Receives pre-made antibodies for short-term protection.
• How it works:
  Antibodies from immune individual → Immediate protection → No memory cells made.
• Examples:
  • Maternal antibodies (through placenta)
  • Antibody injections (e.g., rabies)

Vaccination 

• It is the process of administering a vaccine to help the immune system recognize and defend against harmful pathogens, such as viruses or bacteria, that can cause disease. 
• A vaccine typically contains components or weakened forms of a pathogen (such as viruses, bacteria, or their proteins) that stimulate the immune system without causing illness. Vaccination is a crucial public health tool used to prevent infectious diseases, reduce morbidity and mortality, and contribute to herd immunity.

How Vaccines Work: 

Vaccines work by mimicking the presence of a pathogen (virus, bacteria, or toxin) in a way that stimulates the immune system but does not cause the actual disease. When vaccinated, the body recognizes the foreign substances (antigens) in the vaccine and produces a response. 

1. Introduction of Antigen
   • Vaccine contains antigens (proteins/pieces of pathogen: virus, bacteria, or toxin).
2. Activation of Immune System
   • Antigen Presentation: Antigens are recognized as foreign by the immune system.
   • Immune Cells Activation → B Cells & Antibody Production
   • T Cells stimulate B cells to produce antibodies against the pathogen.
   • Antibodies help neutralize the pathogen.
3. Memory Formation
   • Memory cells (B & T memory cells) are created to “remember” the pathogen.
   • This allows faster immune response if exposed again.
4. Immune Response Without Illness
   • The pathogen in the vaccine is weakened/inactive or just a part of it, preventing illness but stimulating immunity.
5. Herd Immunity:
   • When a significant portion of a population is vaccinated, the spread of the disease slows down because fewer people are susceptible to infection. This protects those who cannot be vaccinated (such as infants, elderly individuals, or those with weakened immune systems). This is known as herd immunity, and it’s especially crucial for diseases with severe complications.

Common Vaccines, Diseases, and Their Administration

Vaccine	Disease(s) Prevented	Administration (Age, Route)
BCG Vaccine	Tuberculosis (TB)	Administered at birth or shortly after birth, intradermal injection
DTP Vaccine	Diphtheria, Tetanus, Pertussis (Whooping Cough)	3 doses at 6, 10, and 14 weeks of age, intramuscular injection
Hepatitis B Vaccine	Hepatitis B, a serious liver infection.	3 doses, first dose at birth, second at 6 weeks, third at 6 months, intramuscular injection
Polio (IPV) Vaccine	Poliomyelitis, a viral infection that can lead to paralysis.	3 doses at 6, 10, and 14 weeks, intramuscular or subcutaneous injection
MMR Vaccine	Measles, Mumps, RubellaMeasles can cause severe complications like encephalitis; mumps can lead to sterility; rubella is especially dangerous in pregnancy.	1st dose at 9-12 months, 2nd dose at 4-6 years, subcutaneous injection
Hepatitis A Vaccine	Hepatitis A	2 doses, first at 1 year, second 6 months later, intramuscular injection
Varicella (Chickenpox) Vaccine	Chickenpox	1st dose at 12-15 months, 2nd dose at 4-6 years, subcutaneous injection
Influenza Vaccine	Influenza (Flu)	Annual vaccination, starting from 6 months, intramuscular or intranasal
HPV Vaccine	Human Papillomavirus (HPV) infections that can lead to cervical cancer, genital warts, and other cancers.	3 doses, first at 11-12 years, second 1-2 months later, third 6 months after first dose, intramuscular injection
Pneumococcal Vaccine	against pneumococcal diseases, including pneumonia, meningitis, and blood infections caused by Streptococcus pneumoniae.	1st dose at 2 months, booster at 12-15 months, intramuscular or subcutaneous injection
Meningococcal Vaccine	Meningococcal Disease (Meningitis)	First dose at 11-12 years, booster at 16 years, intramuscular injection
Rotavirus Vaccine	Rotavirus Infection (causing severe diarrhea)	2-3 doses, starting at 6-8 weeks, oral vaccine
Covishield and Covaxin	Covid-19	Two doses

Types of Vaccines

1. Inactivated (Killed) Vaccines:
   • These vaccines are made from pathogens that have been killed or inactivated so that they cannot cause disease.
   • Examples:
     • Polio vaccine (IPV)
     • Hepatitis A vaccine
     • Rabies vaccine
2. Live Attenuated Vaccines:
   • These vaccines contain live pathogens that have been weakened so they cannot cause serious disease in healthy individuals but still stimulate a strong immune response.
   • Examples:
     • Measles, Mumps, Rubella (MMR) vaccine
     • Yellow fever vaccine
     • Chickenpox (Varicella) vaccine
3. Subunit, Recombinant, or Conjugate Vaccines:
   • These vaccines contain only a part or a piece of the pathogen (such as proteins or sugars) rather than the whole pathogen.
   • Examples:
     • Hepatitis B vaccine
     • Human Papillomavirus (HPV) vaccine
     • Haemophilus influenzae type b (Hib) vaccine
4. DNA or mRNA Vaccines:
   • These newer vaccines use genetic material (either DNA or mRNA) from the pathogen to instruct cells to produce a protein resembling that of the pathogen. The immune system then responds by generating antibodies and memory cells.
   • Examples:
     • COVID-19 mRNA vaccines (Pfizer, Moderna)

Differentiate between Covishield and Covaxin

Characteristic	Covishield	Covaxin
Type	Viral vector vaccine (developed by AstraZeneca)	Inactivated virus vaccine
Manufacturer	Serum Institute of India (SII)	Bharat Biotech
Platform	Uses adenovirus vector	Uses inactivated SARS-CoV-2 virus
Dosage	Requires two doses, typically 4-12 weeks apart	Requires two doses, 4 weeks apart
Efficacy	~70-90% efficacy after two doses	~81% efficacy against symptomatic COVID-19
For Childrens	Only for > 18 year	Available for < 18 years

Name	Corbevax	Covovax
Type	Recombinant protein subunit	Recombinant nanoparticle
Developer	Biological E	Serum Institute (Novavax)
Target Age Group	5-12 years	12-17 years
Mechanism	Spike protein injected, triggers immune response	Simulated spike protein generates immune response
Description	Contains specific part of SARS-CoV-2 virus (spike protein)	Mimics spike protein to elicit immune response

Immunisation Programme

Universal Immunisation Programme (UIP)

• Introduced: 1978 as Expanded Programme of Immunization (EPI).
• Modified: 1985 to Universal Immunization Programme (UIP).
• Purpose: To prevent mortality and morbidity in children and pregnant women against vaccine-preventable diseases.

Mission Indradhanush (MI)

• Launched: 2015 to accelerate immunization coverage to 90%.
• Target: Immunize over 89 lakh children unvaccinated or partially vaccinated.
• Vaccination against 12 Vaccine-Preventable Diseases (VPD) : Diphtheria, Whooping cough, Tetanus, Polio, Tuberculosis, Hepatitis B, Meningitis, Pneumonia, JE, Rotavirus, Pneumococcal conjugate vaccine (PCV), Measles-Rubella (MR).

Intensified Mission Indradhanush (IMI)

1. IMI (October 2017): Focused on urban areas and select districts to ensure 90% immunization by December 2018.
2. IMI 2.0 (2019-20): Nationwide drive, targeting 272 districts with a 90% immunization goal by 2022.
3. IMI 3.0 (2021): Focused on children and pregnant women missed during the Covid-19 pandemic, especially in migration and hard-to-reach areas.
4. IMI 4.0 (2022): Targeted unvaccinated and partially vaccinated children and pregnant women, with three rounds in 416 districts across 33 States/UTs.
5. IMI 5.0 (2023)
   • Aims: Enhance immunization coverage, especially for Measles and Rubella vaccines.
   • Target: Include children up to 5 years of age for the first time.
   • Rounds: 7-12 August, 11-16 September, 9-14 October 2023.
   • Focus: Measles and Rubella elimination by 2023, use of U-WIN digital platform.

India’s immunization program is the largest in the world, covering over 3 crore pregnant women and 2.6 crore children annually.

Monoclonal Antibodies

• Monoclonal antibodies (mAbs) are laboratory-made molecules engineered to serve as substitute antibodies that can restore, enhance, or mimic the immune system’s attack on harmful cells, such as cancer cells or pathogens. 
• Derived from a single clone of immune cells, these antibodies are identical and designed to target specific antigens.
• monoclonal antibody names include: -omab, -ximab, -zumab,-umab.

Types of Monoclonal Antibodies

1. Murine mAbs:
   • Derived entirely from mouse antibodies. Example: OKT3 (used in organ transplant rejection).
2. Chimeric mAbs:
   • Part mouse and part human. Example: Rituximab (used for non-Hodgkin lymphoma).
3. Humanized mAbs:
   • Mostly human, with only the antigen-binding sites from mouse antibodies. Example: Trastuzumab (used for breast cancer).
4. Fully Human mAbs:
   • Entirely human antibodies produced using phage display or transgenic mice. Example: Adalimumab (used for rheumatoid arthritis).

Clinical Applications

• Cancer Treatment:
  • mAbs can specifically target cancer cells, blocking growth signals or marking them for immune destruction.
  • Example: Trastuzumab (Herceptin) targets HER2 in breast cancer.
• Infectious Diseases:
  • mAbs can be used to treat viral or bacterial infections by neutralizing the pathogen.
  • Example: Palivizumab is used to prevent respiratory syncytial virus (RSV) infections in high-risk infants.

• Autoimmune Diseases:
  • mAbs can inhibit specific components of the immune system that attack the body’s own tissues.
  • Example: Adalimumab (Humira) targets TNF-alpha to treat rheumatoid arthritis, Crohn’s disease, and other autoimmune disorders.
• Transplantation:
  • mAbs can be used to prevent organ rejection by targeting immune cells that attack transplanted organs.
  • Example: Muromonab-CD3 targets T-cells to prevent transplant rejection.

Production and Engineering of Monoclonal Antibodies

The evolution of monoclonal antibody production reflects advances in biotechnology:

• Hybridoma Technology.
• Recombinant DNA Technology
• Phage Display Technology
• Transgenic Animals: Animals engineered to produce human antibodies naturally.

FAQ (Previous year questions)