Immunization and Vaccine-Preventable Diseases Practice Questions

Q: BCG vaccine is diluted with:

Normal saline. **Explanation:** The BCG (Bacillus Calmette-Guérin) vaccine is a live attenuated lyophilized (freeze-dried) vaccine. It must be reconstituted before administration using **Normal Saline (0.9% NaCl)** as the specific diluent. **Why Normal Saline?** Normal saline is isotonic and chemically compatible with the live attenuated *Mycobacterium bovis* strain. It maintains the pH and osmotic balance necessary to preserve the viability of the live bacilli. Using the wrong diluent can lead to vaccine failure or increased adverse reactions. **Why other options are incorrect:** * **Distilled Water:** It is hypotonic. Using distilled water causes the live bacilli to swell and burst due to osmotic pressure, rendering the vaccine ineffective. It is also associated with increased local irritation and pain at the injection site. * **Dextrose:** The sugar content can alter the stability of the vaccine and may promote the growth of contaminants once the vial is opened. * **Colloids:** These are large molecular weight substances used for volume expansion and are never used as vaccine diluents. **High-Yield Clinical Pearls for NEET-PG:** * **Reconstitution Rule:** Once reconstituted, the BCG vaccine must be used within **4–6 hours**. Any leftover vaccine must be discarded to prevent contamination (specifically *Staphylococcal* toxic shock syndrome). * **Storage:** The diluent should be stored at the same temperature as the vaccine (**2°C to 8°C**) before mixing to avoid thermal shock to the organisms. * **Other Diluents:** Remember that **Measles/MR** vaccines use **Distilled Water** as a diluent, unlike BCG. * **Site/Route:** BCG is given **Intradermally** (Left Deltoid) using an **Omega/Tuberculin syringe**.

Q: A 20-year-old female diagnosed with acute myeloid leukemia underwent allogeneic stem cell transplantation one year ago. During a follow-up visit, she presents with manifestations of chronic graft-versus-host disease but is otherwise doing well and has no evidence of recurrence. Which of the following vaccines should not be administered to this patient at this point in time?

Measles, mumps, and rubella. **Explanation** The core concept tested here is the contraindication of **live-attenuated vaccines** in immunocompromised individuals. **1. Why "Measles, mumps, and rubella (MMR)" is the correct answer:** MMR is a live-attenuated vaccine. In patients who have undergone Hematopoietic Stem Cell Transplantation (HSCT), live vaccines are strictly contraindicated for at least **24 months** post-transplant. Furthermore, they should only be administered if the patient is free of **Graft-versus-Host Disease (GvHD)** and has been off all immunosuppressive therapy for at least 3–11 months. This patient has active chronic GvHD, making the administration of a live vaccine highly dangerous due to the risk of unchecked viral replication. **2. Why the other options are incorrect:** * **A & D (Diphtheria-tetanus and IPV):** These are **inactivated/killed vaccines** (or toxoids). Inactivated vaccines do not pose a safety risk of causing disease in immunocompromised hosts. Post-HSCT protocols typically recommend restarting the primary series of these vaccines 6–12 months after transplantation. * **B (23-Valent pneumococcal polysaccharide):** This is a subunit/polysaccharide vaccine. It is not live and is actually a high-priority vaccine for HSCT recipients to prevent invasive pneumococcal disease, usually administered starting 6–12 months post-transplant. **Clinical Pearls for NEET-PG:** * **HSCT Rule:** Inactivated vaccines start at **6 months** post-transplant; Live vaccines start at **24 months** (only if no GvHD). * **GvHD Status:** Active GvHD is a definitive contraindication for live vaccines, regardless of the time elapsed since transplant. * **Household Contacts:** Family members of immunocompromised patients *should* receive MMR and Varicella vaccines (to provide herd immunity), but should avoid the Oral Polio Vaccine (OPV) as the virus can be shed in stools. Always prefer **Inactivated Polio Vaccine (IPV)**.

Q: What is the seroconversion rate after completing the 3-dose Hepatitis B vaccine series?

95%. ### Explanation **Correct Answer: D (95%)** The Hepatitis B vaccine is a highly immunogenic, recombinant DNA vaccine containing the Hepatitis B surface antigen (HBsAg). The standard 3-dose schedule (administered at 0, 1, and 6 months) is designed to induce a robust immune response. **Seroconversion** is defined as achieving a protective antibody titer (Anti-HBs) of **≥10 mIU/mL**. In healthy infants, children, and adults under the age of 40, the completion of the 3-dose series results in a protective antibody response in **more than 95%** of recipients. **Analysis of Incorrect Options:** * **Options A (30%) and B (50%):** These rates are significantly lower than the established efficacy of the Hep B vaccine. Such low rates might only be seen in severely immunocompromised individuals or those with end-stage renal disease. * **Option C (70%):** While higher, this still underestimates the vaccine's potency. A 70% response rate might be observed after only two doses, but the third dose is crucial for reaching the >95% threshold and ensuring long-term memory. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Injection:** In adults, it must be given in the **deltoid muscle**. Gluteal injection is avoided as it leads to lower seroconversion rates due to deposition in fat. In infants, the **anterolateral aspect of the thigh** is used. * **Non-responders:** Approximately 5–10% of individuals may not respond to the primary series. Risk factors include age (>40 years), obesity, smoking, and chronic diseases. * **Schedule:** Under the National Immunization Schedule (NIS) in India, it is given at 0, 6, 10, and 14 weeks (as part of the Pentavalent vaccine, plus a birth dose). * **Storage:** It is a **heat-stable but freeze-sensitive** vaccine (stored at +2°C to +8°C). It must never be frozen (Shake Test is used to check if it was frozen).

Q: Zero dose of polio vaccine is given at which point?

At birth. **Explanation:** The term **"Zero Dose"** refers to the dose of Oral Polio Vaccine (OPV) administered **at birth** (or as soon as possible within the first 15 days). **Why "At Birth" is Correct:** The primary objective of the zero dose is to ensure early intestinal immunity before the infant is exposed to enteric pathogens. It overcomes the interference of maternal antibodies and induces local mucosal immunity (IgA) in the gut. It is called "Zero" because it does not count toward the primary three-dose schedule (6, 10, and 14 weeks) required for full protection under the National Immunization Schedule (NIS). **Analysis of Incorrect Options:** * **A. Before giving DPT:** While OPV is co-administered with DPT/Pentavalent at 6, 10, and 14 weeks, the specific "Zero Dose" designation is reserved strictly for the birth dose. * **C. When a child is having diarrhea:** Diarrhea is not a contraindication for OPV. In fact, if a child has diarrhea during a scheduled dose, the dose is given but **not counted**; an extra dose must be administered after recovery. This is a "repeat dose," not a "zero dose." * **D. When a child is having polio:** Vaccination is a preventive measure. If a child already has paralytic poliomyelitis, the vaccine will not cure the condition, though they should still complete their immunization to protect against other strains (P1, P3). **High-Yield Clinical Pearls for NEET-PG:** * **Maximum Age:** OPV Zero dose can be given up to **15 days** of age. * **Type of Vaccine:** OPV is a **Live Attenuated** vaccine (Sabin). * **Storage:** OPV is the most **heat-sensitive** vaccine; it is stored at -20°C (deep freezer) and monitored via the **Vaccine Vial Monitor (VVM)** on the label. * **Current Status:** India currently uses **bOPV** (containing types 1 and 3) in routine immunization, supplemented by **fractional IPV (fIPV)** at 6 and 14 weeks.

Q: Which vaccine should not be administered during pregnancy?

MMR. ### Explanation **Correct Answer: A. MMR** The fundamental principle in obstetric immunization is that **Live Attenuated Vaccines** are generally **contraindicated** during pregnancy. The MMR (Measles, Mumps, and Rubella) vaccine contains live viruses that theoretically pose a risk of transplacental transmission to the fetus. Specifically, the Rubella component carries a theoretical risk of causing Congenital Rubella Syndrome (CRS), although accidental vaccination has rarely shown clinical harm. Women are advised to avoid pregnancy for at least 4 weeks after receiving the MMR vaccine. **Why the other options are incorrect:** * **B. Rabies:** This is a **killed vaccine**. Since rabies is a 100% fatal disease, post-exposure prophylaxis (PEP) is never withheld in pregnancy. It is safe and mandatory if indicated. * **C. Hepatitis B:** This is a **subunit (recombinant) vaccine**. It is not contraindicated and is administered to pregnant women at high risk of infection. * **D. Diphtheria:** Administered as part of the **Tdap or Td** regimen. In India, under the National Immunization Schedule (NIS), two doses of Tetanus and adult Diphtheria (Td) vaccine are standard care to prevent maternal and neonatal tetanus/diphtheria. **High-Yield NEET-PG Pearls:** 1. **Absolute Contraindications in Pregnancy:** MMR, Varicella, Yellow Fever, Zoster, and Live Attenuated Influenza Vaccine (LAIV). 2. **Exception:** Yellow Fever vaccine may be given if the risk of travel to an endemic zone outweighs the risk of vaccination. 3. **Safe Vaccines:** All killed/inactivated vaccines, toxoids (Tetanus, Diphtheria), and recombinant vaccines (Hep B). 4. **Influenza:** The **Inactivated** Influenza Vaccine is specifically recommended for all pregnant women during flu season as they are at high risk for complications.

Q: Rubella vaccination is contraindicated in all except?

Girls between 11-14 years. ### Explanation The core concept tested here is the nature of the **Rubella vaccine**, which is a **Live Attenuated Vaccine** (RA 27/3 strain). Live vaccines are generally contraindicated in individuals with compromised immune systems or during pregnancy due to the theoretical risk of the vaccine virus causing disease or congenital defects. **Why Option C is Correct:** Girls between **11-14 years** (adolescents) are a primary target group for Rubella vaccination. The goal is to provide immunity before they reach childbearing age to prevent **Congenital Rubella Syndrome (CRS)**. While the vaccine is contraindicated *during* pregnancy, it is highly recommended for non-pregnant adolescent girls and women of reproductive age. **Why the Other Options are Wrong:** * **Option A (Immunosuppressants):** Live vaccines can cause uncontrolled replication of the vaccine virus in patients on high-dose corticosteroids or chemotherapy, leading to severe systemic infection. * **Option B (Leukemia):** Malignancies of the immune system (like leukemia or lymphoma) are absolute contraindications for live vaccines because the host cannot mount an effective response to contain the attenuated virus. * **Option C (Pregnancy):** There is a theoretical risk of the live virus crossing the placenta and causing CRS. Therefore, pregnancy is a contraindication, and pregnancy should be avoided for **1 month** (formerly 3 months) after vaccination. **High-Yield NEET-PG Pearls:** * **Vaccine Strain:** RA 27/3 (grown in human diploid cells). * **Dose/Route:** 0.5 ml, Subcutaneous. * **Storage:** Most sensitive to light (must be protected). * **CRS Prevention:** The primary objective of Rubella vaccination is not just to protect the individual, but to prevent fetal infection in utero. * **Post-Exposure:** Rubella vaccine does not provide post-exposure prophylaxis (unlike Measles).

Q: Under the national polio eradication program, after how many days is a case of acute flaccid paralysis confirmed as polio by surveillance?

60 days. ### Explanation The correct answer is **60 days**. Under the **Global Polio Eradication Initiative (GPEI)** and India’s National Surveillance program, the confirmation of a case as "Polio" or "Non-Polio AFP" is based on the presence of **residual paralysis**. 1. **Why 60 days is correct:** Acute Flaccid Paralysis (AFP) can be caused by various etiologies (e.g., Guillain-Barré Syndrome, Transverse Myelitis). However, paralysis caused by the Poliovirus is typically permanent. Therefore, the protocol mandates a **60-day follow-up examination**. If the child still exhibits weakness or paralysis after 60 days, the case is clinically compatible with polio (if virological tests were inconclusive) or confirmed as polio (if wild poliovirus was isolated). 2. **Why other options are incorrect:** * **15 days:** This is the window for "adequate stool collection." Two stool samples must be collected 24–48 hours apart within 14 days of the onset of paralysis. * **30 days:** This is too early to determine if paralysis is permanent, as many non-polio AFP cases show significant recovery within a month. * **90 days:** While follow-up can occur later, the standard surveillance milestone for classification is 60 days. ### High-Yield Clinical Pearls for NEET-PG: * **AFP Surveillance Criteria:** Includes any child <15 years with sudden onset of flaccid paralysis or a person of any age where polio is suspected. * **Stool Samples:** Must be sent under "Reverse Cold Chain" (maintained at 2–8°C) to the laboratory. * **Zero Polio Status:** India was declared Polio-free by the WHO on **March 27, 2014**, after three consecutive years of zero indigenous cases (last case: Jan 13, 2011, in Howrah, West Bengal). * **Vaccine Change:** India switched from Trivalent OPV to **Bivalent OPV** (containing types 1 and 3) in April 2016, alongside the introduction of **Inactivated Polio Vaccine (IPV)**.

Q: If a mother is vaccinated for rubella in the preconception period, what is the recommended waiting period before conception to ensure optimal protection against rubella infection in the child?

6 months. ### Explanation **Correct Answer: C. 6 months** **Concept:** The Rubella vaccine is a **live-attenuated vaccine** (RA 27/3 strain). The primary concern with administering live vaccines near or during pregnancy is the theoretical risk of the vaccine virus crossing the placenta and causing **Congenital Rubella Syndrome (CRS)**. While the CDC and WHO suggest a minimum waiting period of 28 days (1 month), the **National Guidelines in India** and several standard textbooks used for NEET-PG (like Park’s Preventive and Social Medicine) traditionally recommend a safer margin of **6 months** to ensure complete clearance of the virus and robust antibody development before conception. **Analysis of Options:** * **Option A (1 month):** This is the minimum period recommended by international bodies (CDC/WHO). However, for Indian competitive exams, the more conservative 6-month window is the standard "textbook" answer. * **Option B (2 months):** This is an intermediate duration and is not a standard guideline for Rubella. * **Option D (12 months):** This is unnecessarily long. Protective immunity is established much earlier, and delaying pregnancy for a year is clinically unwarranted. **High-Yield Clinical Pearls for NEET-PG:** * **Strain used:** RA 27/3 (Human diploid cell culture). * **Contraindication:** Pregnancy is an absolute contraindication for the MMR/Rubella vaccine. * **Accidental Vaccination:** If a pregnant woman is accidentally vaccinated, it is **not** an indication for Medical Termination of Pregnancy (MTP), as the actual risk of CRS from the vaccine strain is negligible. * **Post-partum Vaccination:** The best time to vaccinate a woman of reproductive age is immediately after delivery (post-partum), as there is no risk of pregnancy in the immediate period. * **Storage:** Must be stored at +2°C to +8°C and protected from light.

Question 1

BCG vaccine is diluted with:

Accepted Answer

Normal saline

Answer

Distilled water

Answer

Dextrose

Answer

Colloids

Question 2

A 20-year-old female diagnosed with acute myeloid leukemia underwent allogeneic stem cell transplantation one year ago. During a follow-up visit, she presents with manifestations of chronic graft-versus-host disease but is otherwise doing well and has no evidence of recurrence. Which of the following vaccines should not be administered to this patient at this point in time?

Accepted Answer

Measles, mumps, and rubella

Answer

Diphtheria-tetanus

Answer

23-Valent pneumococcal polysaccharide

Answer

Poliomyelitis injection

Question 3

What is the seroconversion rate after completing the 3-dose Hepatitis B vaccine series?

Accepted Answer

95%

Answer

30%

Answer

50%

Answer

70%

Question 4

Zero dose of polio vaccine is given at which point?

Accepted Answer

At birth

Answer

Before giving DPT

Answer

When a child is having diarrhea

Answer

When a child is having polio

Question 5

Which vaccine should not be administered during pregnancy?

Accepted Answer

MMR

Answer

Rabies

Answer

Hepatitis B

Answer

Diphtheria

Question 6

Which of the following statements regarding the oral polio vaccine (OPV) is not true?

Accepted Answer

Excretion of the virus in stools can lead to disease in the unimmunized

Answer

Useful in epidemics

Answer

Provides a rapid antibody response

Answer

Protective even in the presence of maternal antibodies

Question 7

Rubella vaccination is contraindicated in all except?

Accepted Answer

Girls between 11-14 years

Answer

Patient on immunosuppressants

Answer

Girl with leukemia

Answer

Pregnancy

Question 8

Under the national polio eradication program, after how many days is a case of acute flaccid paralysis confirmed as polio by surveillance?

Accepted Answer

60 days

Answer

15 days

Answer

30 days

Answer

90 days

Question 9

Which of the following is NOT true regarding the surveillance of acute flaccid paralysis in the context of a national polio eradication program?

Accepted Answer

A follow-up examination should be conducted 30 days after the onset of paralysis.

Answer

Acute flaccid paralysis is defined in a child less than 15 years of age.

Answer

All cases of acute flaccid paralysis should be reported irrespective of diagnosis within 6 months of onset.

Answer

Two stool specimens should be collected within 14 days of paralysis onset, at least 24 hours apart.

Question 10

If a mother is vaccinated for rubella in the preconception period, what is the recommended waiting period before conception to ensure optimal protection against rubella infection in the child?

Accepted Answer

6 months

Answer

1 month

Answer

2 months

Answer

12 months

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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