Quick Answer
Vaccination contributes 4–6 NEET PG questions per paper — primarily from PSM and pediatrics. Master these 8 high-yield areas:
- UIP schedule — BCG, Hep B birth dose, OPV at birth/6/10/14 weeks, IPV, pentavalent (DPT-HepB-Hib) at 6/10/14 weeks, rotavirus, PCV, MR at 9 and 16–24 months, JE in endemic areas, DPT booster at 16–24 months and 5–6 years, Td/TT
- Vaccine types — live attenuated (BCG, OPV, MMR, MR, varicella, rotavirus, JE-live), inactivated/killed (IPV, Hep A, rabies, pertussis whole-cell), subunit (HepB, acellular pertussis, HPV, pneumococcal), conjugate (Hib, PCV, MenACWY), toxoid (DT, TT, Td), mRNA (Pfizer, Moderna COVID), viral vector (Covishield, Sputnik, Janssen)
- Cold chain — most vaccines 2–8°C, OPV at -15 to -25°C; VVM monitors heat exposure; ice-lined refrigerator at PHC level
- Live vaccine contraindications — pregnancy, severe immunocompromise (CD4 <200), high-dose steroids, HIV symptomatic
- Adverse events — BCG (regional adenitis, ulceration), DPT (encephalopathy = contraindication for next dose), rotavirus (intussusception risk <1/100,000), MMR (febrile seizure, thrombocytopenia)
- COVID-19 vaccines — Covaxin (whole inactivated), Covishield (ChAdOx1 viral vector), Corbevax (subunit), Sputnik V (Ad26+Ad5), heterologous mRNA (Pfizer, Moderna)
- HPV — quadrivalent or 9-valent, ages 9–26, 2 or 3 doses; India's indigenous CERVAVAC launched 2023
- Rotavirus — RotaSiil and Rotavac (live attenuated, oral), 3 doses at 6/10/14 weeks; intussusception risk
Immunization is the highest-yield single topic in PSM and pediatrics combined for NEET PG — typically 4–6 direct questions per paper. Examiners test the UIP schedule, IAP additions, cold chain temperatures, live versus killed classification, and contraindications. The candidate who memorises this NEETPGAI guide effectively converts a guaranteed cluster of marks into reflex answers.
This deep dive covers India-specific UIP and IAP schedules, every major vaccine class, the cold chain hierarchy, COVID-19 era updates including CERVAVAC and indigenous platforms, and the contraindications NBE loves to test. Pair with the PSM high-yield topics guide and pediatrics high-yield topics for cross-coverage.
Vaccine types and classification
Vaccines are antigenic preparations that elicit protective immunity without causing disease. Their classification by antigen design predicts cold chain needs, contraindications, and adverse events.
Live attenuated vaccines
These contain weakened live organisms that replicate but cannot cause disease in immunocompetent hosts. They induce strong, long-lasting immunity (often single-dose) that mimics natural infection.
- Examples: BCG, OPV, MMR (measles, mumps, rubella), MR, varicella, rotavirus, yellow fever, oral typhoid (Ty21a), JE-live, intranasal influenza (LAIV), zoster live
- Contraindications: Pregnancy (theoretical risk), severe immunocompromise (CD4 <200, high-dose steroids ≥20 mg prednisone for ≥14 days, biologics, transplant)
- Spacing rule: Two live parenteral vaccines must be given simultaneously OR separated by ≥4 weeks (otherwise interferon from the first blunts the second)
Inactivated (killed) vaccines
Whole organisms killed by heat, formalin, or beta-propiolactone. Cannot replicate, so safe in pregnancy and immunocompromise, but require multiple doses for durable immunity.
- Examples: IPV (Salk), Hep A, whole-cell pertussis (in DPT), rabies, JE-Vero cell, cholera (Shanchol), influenza (most formulations)
Subunit / recombinant vaccines
Contain only antigenic fragments — proteins, polysaccharides, or genetically engineered antigens.
- Recombinant protein: Hepatitis B (HBsAg from yeast), HPV (L1 capsid VLP from yeast)
- Acellular pertussis: Purified PT, FHA, pertactin, fimbriae
- Polysaccharide: Plain pneumococcal (PPSV23), meningococcal polysaccharide (T-cell independent — poor in <2 years)
- Conjugate: Polysaccharide chemically linked to protein carrier (Hib-CRM197, PCV13/15/20, MenACWY-DT, typhoid Vi-TT) — induces T-cell-dependent memory, effective in infants
Toxoid vaccines
Bacterial exotoxins inactivated by formaldehyde while preserving antigenicity.
- Examples: Diphtheria toxoid, tetanus toxoid (TT, Td), used in DPT, DT, TT, Tdap
Newer platforms (post-COVID)
- mRNA vaccines (Pfizer-BioNTech BNT162b2, Moderna mRNA-1273) — lipid nanoparticle-encapsulated mRNA encoding spike protein
- Viral vector vaccines (Covishield/AstraZeneca ChAdOx1-S, Sputnik V Ad26+Ad5, Janssen Ad26.COV2.S) — non-replicating adenovirus carrying spike gene
- Subunit COVID vaccines (Corbevax — RBD on alum + CpG, Novavax — recombinant spike + Matrix-M)
- Whole-virion inactivated (Covaxin/BBV152 — inactivated SARS-CoV-2 + Algel-IMDG)
Universal Immunization Programme (UIP) schedule — India
UIP is the Government of India free immunization programme covering 12 vaccine-preventable diseases. The schedule is the single most tested PSM topic.
| Age | Vaccines |
|---|
| At birth | BCG, OPV-0 (zero dose), Hep B birth dose (within 24 hr) |
| 6 weeks | OPV-1, Pentavalent-1 (DPT + HepB + Hib), Rotavirus-1, fIPV-1 (fractional IPV), PCV-1 |
| 10 weeks | OPV-2, Pentavalent-2, Rotavirus-2 |
| 14 weeks | OPV-3, Pentavalent-3, Rotavirus-3, fIPV-2, PCV-2 |
| 9 months | MR-1 (measles-rubella), JE-1 (in endemic districts), PCV-booster, Vitamin A first dose |
| 16–24 months | DPT booster-1, OPV booster, MR-2, JE-2 |
| 5–6 years | DPT booster-2 |
| 10 years | Td (replaces TT) |
| 16 years | Td |
| Pregnancy | Td (2 doses or 1 booster), TT historically |
Mission Indradhanush
Launched 2014 to achieve full immunization coverage of children <2 years and pregnant women. Intensified Mission Indradhanush (IMI) targets low-coverage districts. IMI 5.0 (2023) added measles-rubella elimination focus.
IAP (Indian Academy of Pediatrics) additions
Beyond UIP, IAP recommends private-sector additional vaccines:
- Hepatitis A — 2 doses at 12 and 18 months (or single dose live attenuated)
- Varicella — 2 doses at 15 months and 4–6 years
- Typhoid conjugate (TCV) — single dose at 9–12 months, booster at 2 years
- Influenza — annual from 6 months
- HPV — 9–14 years (2 doses), 15–26 years (3 doses)
- MMR instead of MR (added mumps coverage)
- Hib booster at 16–18 months
Cold chain — temperature and equipment
Cold chain is the temperature-controlled supply chain (manufacturer → state → district → PHC → field) ensuring vaccine potency.
| Storage level | Equipment | Temperature |
|---|
| Government Medical Store Depot (GMSD) | Walk-in cooler, walk-in freezer | 2–8°C / -15 to -25°C |
| State / Regional Vaccine Store | Walk-in cooler, deep freezer | 2–8°C / -15 to -25°C |
| District Vaccine Store | Ice-lined refrigerator (ILR), deep freezer | 2–8°C / -15 to -25°C |
| PHC | ILR + deep freezer | 2–8°C |
| Sub-centre / outreach | Cold box, vaccine carrier with conditioned ice packs | 2–8°C for 24–48 hr |
| Day of session | Vaccine carrier with 4 ice packs | 2–8°C |
Vaccine sensitivity to temperature
| Most heat-sensitive | Most cold-sensitive (freezing damages) |
|---|
| OPV, BCG (after reconstitution) | Hep B, DPT, Td, IPV, pentavalent |
| Measles, MR | All adsorbed (alum-containing) vaccines |
OPV is the most heat-sensitive vaccine — requires deep freeze at -15 to -25°C; once thawed, use within 1 hour.
Hepatitis B and DPT are damaged by freezing — never store in deep freezer; use the Shake test to identify frozen DPT (flocculent sediment that does not redisperse).
Vaccine Vial Monitor (VVM)
A heat-sensitive square inside a circle on the vaccine label. As cumulative heat exposure increases, the inner square darkens.
- Stage 1–2: Inner square lighter than outer circle → use the vial
- Stage 3: Inner square matches outer circle → DISCARD point — do not use
- Stage 4: Inner square darker than outer circle → DISCARD
Open Vial Policy (2014)
Multi-dose vials of OPV, DPT, TT, Hep B, pentavalent (without preservative — currently with thiomersal), and fIPV may be used in subsequent sessions for up to 4 weeks if: (1) VVM has not crossed discard point, (2) expiry date not passed, (3) vial not contaminated, (4) septum intact, (5) stored at 2–8°C between sessions. BCG, measles, MR, JE, rotavirus do NOT qualify (must be discarded after 4 hours).
Contraindications and adverse events
Absolute contraindications
- Anaphylaxis to a previous dose or to a vaccine component (egg protein for yellow fever and some influenza, gelatin, neomycin, latex)
- Encephalopathy within 7 days of a previous pertussis dose — contraindicates further pertussis-containing vaccines (give DT instead of DPT)
- Severe immunocompromise for live vaccines
NOT contraindications (commonly mistaken)
- Mild illness with low-grade fever
- Antibiotic use (most antibiotics, except oral typhoid live)
- Lactation (most vaccines safe)
- Prematurity (give vaccines at chronological age, not corrected age)
- Family history of seizures or SIDS
- Egg allergy alone (most influenza vaccines now safe; check yellow fever and rabies)
Adverse Events Following Immunization (AEFI) classification (WHO 2018)
- Vaccine product-related — caused by inherent property of vaccine (e.g., vaccine-derived poliovirus from OPV)
- Vaccine quality defect-related — manufacturing fault
- Immunization error-related (programme error) — improper handling, wrong site, wrong reconstitution
- Immunization anxiety-related — vasovagal, breath-holding
- Coincidental — temporally associated but unrelated
Notable vaccine-specific adverse events
| Vaccine | Adverse event | Frequency |
|---|
| BCG | Regional adenitis, lupus vulgaris, BCG osteomyelitis (rare) | Adenitis 1–10% |
| OPV | Vaccine-associated paralytic polio (VAPP), vaccine-derived poliovirus (cVDPV) | VAPP 1 in 2.7 million |
| DPT (whole cell) | Encephalopathy, seizures, persistent crying >3 hr, HHE | Encephalopathy 1 in 110,000 |
| MMR / MR | Febrile seizure (5–12 days), thrombocytopenia, transient arthralgia | Seizure 1 in 3000 |
| Rotavirus | Intussusception (RotaShield withdrawn; current vaccines very low risk) | 1 in 30,000–100,000 |
| HPV | Syncope (post-injection), local pain | Syncope 8% |
| mRNA COVID | Myocarditis (young males, 2nd dose), anaphylaxis | Myocarditis 1 in 6,000 (12–17 yr males) |
| ChAdOx1 (Covishield) | TTS (thrombosis with thrombocytopenia syndrome) | 1 in 100,000 |
Special populations
Pregnancy
- Safe (recommended): Tdap (every pregnancy at 27–36 weeks for neonatal pertussis prevention), inactivated influenza, COVID-19 mRNA, hepatitis B
- Contraindicated: All live vaccines (MMR, varicella, BCG, OPV, yellow fever, LAIV)
- Conditional: Hepatitis A, meningococcal, rabies if exposure risk
HIV-infected children
- CD4 ≥15% (or ≥200): Most live vaccines acceptable except OPV (use IPV); MR, varicella, MMR can be given
- CD4 <15% or symptomatic AIDS: Avoid all live vaccines; killed vaccines safe but with reduced response
- BCG: WHO advises against in HIV-exposed infants until status known; if HIV-positive, contraindicated due to disseminated BCG risk
Immunocompromised hosts (transplant, chemotherapy, biologics)
- Inactivated vaccines: safe but suboptimal response
- Live vaccines: contraindicated; family contacts CAN receive live vaccines (except OPV — household contact risk of VAPP)
Recent updates and guidelines
- CERVAVAC (HPV) — India's first indigenous quadrivalent HPV vaccine launched 2023, manufactured by Serum Institute; phased UIP rollout in 2025–2026.
- Polio endgame — global switch from tOPV to bOPV (April 2016) and phased introduction of IPV; India remains polio-free since 2014, certified 2014.
- Measles-rubella elimination — India target 2026; MR-1 at 9 months replaced measles monovalent, MR-2 at 16–24 months.
- Typhoid conjugate vaccine (TCV) — Typbar-TCV included in IAP 2018; phased UIP introduction in select districts.
- PCV introduction completed nationally 2021 (PCV13).
- COVID-19 schedule — primary 2-dose Covaxin / Covishield + booster (precaution dose); Corbevax used as heterologous booster after primary Covaxin/Covishield.
- Dengue vaccine — Dengvaxia approved internationally but limited use due to seronegative risk; indigenous tetravalent vaccines in trials.
- Malaria vaccine — RTS,S (Mosquirix) and R21/Matrix-M WHO-recommended for sub-Saharan Africa; no India deployment.
High-yield NEET PG MCQ traps
- OPV-0 is given only at birth in institutional deliveries; not given after 6 weeks (use bOPV thereafter).
- fIPV (fractional IPV) is intradermal — given at 6 and 14 weeks alongside OPV.
- Pentavalent vaccine = DPT + HepB + Hib (NOT IPV).
- MR replaces measles-only vaccine in UIP from 2017 onwards — first dose at 9 months.
- JE vaccine is given only in endemic districts at 9 and 16–24 months (live attenuated SA 14-14-2).
- Td replaces TT in adolescents and pregnancy from 2018 (better diphtheria coverage).
- BCG is given intradermally over the left deltoid (NOT subcutaneous, NOT in the right arm — left side reserves room for smallpox-era scarring conventions).
- Reconstituted vaccines (BCG, MR, MMR, JE) discarded after 4 hours OR end of session, whichever earlier.
- Hep B birth dose must be within 24 hours (ideally) — beyond 7 days, the dose counts as primary not birth.
- Open vial policy does NOT apply to BCG, MR, JE, rotavirus.
Frequently asked questions
What is the difference between UIP and IAP immunization schedules?
UIP (Universal Immunization Programme) is the Government of India schedule offering free vaccines to all infants under 2 years and pregnant women — it covers 12 diseases. IAP (Indian Academy of Pediatrics) is broader, including additional vaccines like rotavirus, varicella, hepatitis A, HPV, influenza, and typhoid for private practice.
Which vaccines are live attenuated and contraindicated in pregnancy?
Live attenuated vaccines contraindicated in pregnancy: MMR, varicella, BCG, oral polio (OPV), oral typhoid, yellow fever, intranasal influenza (LAIV), rotavirus. Also avoid in immunocompromised patients. Inactivated vaccines (Tdap, IPV, Hep B, COVID-19, Hib) are safe in pregnancy.
What is cold chain and what temperature range is required?
Cold chain is the system maintaining vaccines at 2–8°C from manufacturer to point of administration. OPV requires deep-freeze at -15 to -25°C. Vaccine vial monitor (VVM) shows heat exposure — discard if inner square equals or exceeds outer circle. Walk-in coolers, ILRs, and cold boxes form the chain components.
When should HPV vaccine be given for NEET PG context?
HPV vaccine (quadrivalent or 9-valent) is recommended at ages 9–14 years for girls, ideally before sexual debut. Two-dose schedule (0, 6 months) for ages 9–14; three-dose (0, 1–2, 6 months) for ages 15–26. India launched indigenous CERVAVAC quadrivalent vaccine in 2023, now part of select state UIP rollouts.
What are the absolute contraindications to vaccination?
Absolute contraindications: anaphylaxis to a previous dose or vaccine component (egg protein for some, gelatin, neomycin), encephalopathy within 7 days of pertussis vaccine (DPT). Severe immunocompromise contraindicates live vaccines. Mild illness, antibiotic use, lactation, prematurity, and family history of seizures are NOT contraindications.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
Written by: NEETPGAI Editorial Team
Reviewed by: Pending SME Review
Last reviewed: April 2026
