1. What is the difference between prophylactic and therapeutic vaccines?

Prophylactic vaccines are designed to prevent a disease before exposure to the pathogen. They prime the immune system to recognize and fight off future infections, thereby preventing illness. Examples include vaccines for measles, polio, and influenza. Therapeutic vaccines, in contrast, are administered after a disease has already occurred. Their goal is to treat an existing condition by stimulating the immune system to attack diseased cells, such as cancer cells or chronically infected cells. An example is Sipuleucel-T for prostate cancer, which aims to help the patient's immune system target cancer cells. While prophylactic vaccines are a cornerstone of public health, therapeutic vaccines represent a frontier in personalized medicine, particularly in oncology.

2. How do mRNA vaccines like Pfizer and Moderna work?

mRNA vaccines work by delivering a piece of messenger RNA (mRNA) that contains instructions for making a specific protein from the pathogen (e.g., the spike protein of SARS-CoV-2). This mRNA is encapsulated in lipid nanoparticles to protect it and facilitate entry into human cells. Once inside the cells, the cellular machinery reads the mRNA instructions and produces the pathogen's protein. This protein is then displayed on the cell surface, triggering an immune response. The immune system recognizes this protein as foreign and produces antibodies and T-cells against it. The mRNA itself is quickly degraded and does not enter the cell's nucleus or alter DNA. This process effectively 'teaches' the immune system to recognize and fight the actual pathogen without ever introducing the live virus.

3. What are the main types of cancer immunotherapy?

The main types of cancer immunotherapy include: 1. **Monoclonal Antibodies (mAbs):** Engineered antibodies that target specific molecules on cancer cells or immune cells to block growth, deliver toxins, or unmask cancer cells. 2. **Immune Checkpoint Inhibitors:** A type of mAb that blocks proteins (like PD-1, PD-L1, CTLA-4) that cancer cells use to 'turn off' immune cells, thereby releasing the immune system's brakes. 3. **CAR-T Cell Therapy:** A personalized treatment where a patient's T cells are genetically modified to express Chimeric Antigen Receptors (CARs) that specifically target and kill cancer cells. 4. **Therapeutic Cancer Vaccines:** Aim to stimulate the patient's immune system to recognize and attack existing cancer cells by presenting tumor-specific antigens. 5. **Adoptive Cell Therapy (ACT):** Involves isolating, expanding, and re-infusing immune cells to enhance anti-tumor activity.

4. Which COVID-19 vaccines are manufactured in India?

Several COVID-19 vaccines have been manufactured in India. The most prominent ones include: **Covishield**, which is the AstraZeneca/Oxford viral vector vaccine manufactured by the Serum Institute of India (SII), the world's largest vaccine manufacturer. **Covaxin**, an inactivated whole-virion vaccine, was indigenously developed and manufactured by Bharat Biotech in collaboration with the Indian Council of Medical Research (ICMR) and the National Institute of Virology (NIV). Additionally, **Sputnik V**, a viral vector vaccine developed by Russia's Gamaleya Research Institute, was also manufactured in India by Dr. Reddy's Laboratories. India has also been developing its own mRNA vaccine, GEMCOVAC-19, by Gennova Biopharmaceuticals.

5. What is herd immunity and how is the threshold calculated?

Herd immunity, or community immunity, occurs when a sufficient percentage of a population becomes immune to an infectious disease, either through vaccination or prior infection, making the spread of the disease from person to person unlikely. This indirectly protects individuals who are not immune, such as infants or immunocompromised persons. The herd immunity threshold is the proportion of the population that needs to be immune to achieve this protection. It is calculated using the basic reproduction number (R0) of the pathogen, which is the average number of people an infected person will infect in a susceptible population. The formula is typically 1 - (1/R0). For example, if R0 is 3, the threshold is 1 - (1/3) = 0.67 or 67%. A higher R0 requires a higher vaccination coverage for herd immunity.

6. How are vaccine side effects monitored and reported (AEFI)?

Vaccine side effects are monitored through robust pharmacovigilance systems, primarily focusing on Adverse Events Following Immunization (AEFI). In India, the AEFI surveillance system, managed by the Ministry of Health and Family Welfare, collects and analyzes reports of adverse events. Healthcare professionals, vaccine recipients, and their families can report suspected side effects. These reports are then investigated to determine if there's a causal link to the vaccine or if it's a coincidental event. The data is crucial for ensuring vaccine safety, identifying rare side effects, and maintaining public trust. This continuous monitoring helps regulatory bodies like CDSCO make informed decisions about vaccine use and update safety guidelines.

7. What role does India play in global vaccine manufacturing?

India plays a pivotal role in global vaccine manufacturing, often referred to as the 'pharmacy of the world.' It is the largest producer of vaccines globally by volume, supplying over 60% of the world's vaccines. Companies like the Serum Institute of India (SII) and Bharat Biotech are major players, producing vaccines for various diseases, including measles, polio, diphtheria, and tetanus, and playing a critical role during the COVID-19 pandemic. India's robust manufacturing capacity, cost-effectiveness, and quality standards make it a crucial supplier for UNICEF, Gavi (the Vaccine Alliance), and numerous developing countries, significantly contributing to global health security and equitable access to vaccines, exemplified by initiatives like 'Vaccine Maitri'.

8. How long does vaccine immunity last?

The duration of vaccine-induced immunity varies significantly depending on the vaccine, the pathogen, and individual factors. For some vaccines, like measles or polio, immunity can be lifelong after a full course. For others, like tetanus or influenza, booster shots are required periodically (e.g., every 10 years for tetanus, annually for influenza) because immunity wanes over time or the pathogen evolves. Factors influencing duration include the type of vaccine (live attenuated often provides longer immunity), the strength of the initial immune response, and the presence of circulating pathogens that can naturally boost immunity. Research continuously monitors immunity duration to inform vaccination schedules.

9. What is Antibody-Dependent Enhancement (ADE) and why was it a concern for COVID-19 vaccines?

Antibody-Dependent Enhancement (ADE) is a phenomenon where antibodies, instead of neutralizing a virus, actually enhance its entry into host cells and/or replication, potentially leading to more severe disease. This can occur if antibodies bind to the virus but are non-neutralizing or sub-neutralizing. ADE has been observed with some viral diseases like Dengue fever. For COVID-19, there was an initial theoretical concern that vaccines might induce ADE, potentially worsening disease upon subsequent infection. However, extensive pre-clinical and clinical trials, and real-world data from millions of vaccinated individuals, have shown no evidence of ADE with any of the approved COVID-19 vaccines. The induced antibodies are overwhelmingly protective and neutralizing.

10. What are the ethical considerations in vaccine development and distribution?

Ethical considerations in vaccine development and distribution are multifaceted. They include: 1. **Informed Consent:** Ensuring participants in clinical trials fully understand risks and benefits. 2. **Equitable Access:** Addressing disparities in vaccine availability between rich and poor nations. 3. **Prioritization:** Deciding who gets vaccines first when supply is limited. 4. **Transparency:** Openly sharing data on safety and efficacy. 5. **Pharmacovigilance:** Robust monitoring of adverse events. 6. **Vaccine Mandates:** Balancing individual autonomy with public health needs. 7. **Research Ethics:** Ensuring fair treatment of vulnerable populations in trials. These considerations are crucial for maintaining public trust and achieving global health equity.

Vaccines and Immunotherapy

Science & Technology

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Version 1Updated 10 Mar 2026

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The Drugs and Cosmetics Act, 1940, and its associated Rules, particularly the New Drugs and Clinical Trials Rules, 2019, form the bedrock of regulatory oversight for vaccines and immunotherapeutic agents in India. These legislative frameworks, administered by the Central Drugs Standard Control Organisation (CDSCO), mandate rigorous pre-clinical and clinical testing, manufacturing standards (Good M…

Quick Summary

Vaccines and immunotherapy are critical biomedical interventions that leverage the body's immune system to combat diseases. Vaccines are primarily prophylactic, meaning they prevent infectious diseases by introducing weakened, inactivated, or partial components of a pathogen to 'train' the immune system.

This training leads to the production of antibodies and memory cells, enabling a rapid and effective response upon future exposure to the actual pathogen. Key vaccine types include live attenuated (e.g.

, MMR), inactivated (e.g., Covaxin), subunit (e.g., Hepatitis B), mRNA (e.g., Pfizer-BioNTech), and viral vector (e.g., Covishield) vaccines, each with distinct mechanisms, advantages, and storage requirements.

The development of mRNA and viral vector platforms during the COVID-19 pandemic showcased rapid innovation and adaptability in vaccinology.

Immunotherapy, conversely, is largely therapeutic, aiming to treat existing diseases, predominantly cancer, by modulating or enhancing the patient's own immune response. Cancer cells often evade immune detection, and immunotherapy strategies seek to overcome this.

Major approaches include monoclonal antibodies (mAbs) like Rituximab and Pembrolizumab, which target specific cancer cell markers or immune checkpoints; immune checkpoint inhibitors that 'release the brakes' on T cells; and advanced cell therapies like CAR-T cell therapy, where a patient's T cells are genetically engineered to specifically recognize and destroy cancer cells.

While offering revolutionary treatment options, immunotherapies can have significant side effects, such as cytokine release syndrome, and pose challenges related to cost and access. India plays a crucial role in global vaccine manufacturing, with companies like Serum Institute of India and Bharat Biotech being major producers.

The country's regulatory framework, governed by CDSCO under the Drugs and Cosmetics Act, 1940, ensures the safety and efficacy of these biological products. Ethical considerations like informed consent, equitable access, and pharmacovigilance are paramount in the development and deployment of both vaccines and immunotherapies.

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Key Facts:

Vaccines: — Prophylactic, prime immune system. Types: Live attenuated (MMR, OPV), Inactivated (Covaxin, IPV), Subunit (Hep B), mRNA (Pfizer, Moderna), Viral Vector (Covishield, Sputnik V).

Immunotherapy: — Therapeutic, modulate immune system. Types: Monoclonal Antibodies (Rituximab, Pembrolizumab), Checkpoint Inhibitors (PD-1/CTLA-4), CAR-T Cell Therapy.

India: — Largest vaccine producer (SII, Bharat Biotech). Mission Indradhanush (immunization). National Vaccine Policy 2011. CDSCO (regulator). Vaccine Maitri (diplomacy).

COVID-19: — mRNA (ultra-cold), Viral Vector (refrigerator stable), Inactivated (traditional).

CAR-T: — Personalized, for blood cancers, risk of Cytokine Release Syndrome (CRS). First indigenous CAR-T (NexCAR19) approved in India (2023).

Ethics: — Informed consent, equitable access, pharmacovigilance (AEFI), vaccine hesitancy.

VACCI-IMMUNE for Vaccines & Immunotherapy:

Vaccine Always Combats Cancer Infections - Immunotherapy Modulates My Unique Natural Energy.

VACCINE TYPES (LIMS-VV):

Live Attenuated

Inactivated

MRNA

Subunit

Viral Vector

IMMUNOTHERAPY (CAR-CHECK-MONO):

CAR — T Cell Therapy

CHECKpoint Inhibitors

MONOclonal Antibodies

INDIA's VACCINE ROLE (MIMIC):

Manufacturing Hub

Indradhanush (Mission)

Maitri (Vaccine Diplomacy)

Indigenous R&D

CDSCO (Regulation)

Visual Memory Aids:

Vaccine Cold Chain Infographic: — A diagram showing different temperature zones for vaccine storage (e.g., -70°C for mRNA, 2-8°C for others) from factory to arm.

CAR-T Cell Therapy Workflow: — A flowchart illustrating the steps: apheresis -> T-cell engineering -> expansion -> infusion -> cancer cell killing.

Immune Checkpoint Inhibitor Diagram: — A visual showing T-cell with 'brakes' (PD-1) and cancer cell with 'accelerator' (PD-L1), and how inhibitors block the interaction to 'release the brake'.