Immunization for MCCQE1
Introduction
Immunization is a cornerstone of Canadian public health and a high-yield topic for the MCCQE1. As a future physician, you are expected to demonstrate the CanMEDS roles of Health Advocate and Communicator by effectively counseling patients on vaccine benefits, managing schedules, and addressing vaccine hesitancy.
This guide covers the essential immunological principles, the Canadian Immunization Guide (CIG) recommendations, special populations, and post-exposure prophylaxis protocols required for the MCCQE1 preparation.
🇨🇦 Canadian Context: The NACI
In Canada, the National Advisory Committee on Immunization (NACI) provides medical, scientific, and public health advice. However, healthcare delivery is a provincial responsibility. While the CIG is the national standard, always remember that provincial schedules may vary slightly. For MCCQE1 purposes, focus on the national CIG recommendations.
Basic Concepts of Immunity
Understanding the difference between active and passive immunity is crucial for determining the appropriate prophylaxis (e.g., Vaccine vs. Immunoglobulin).
Active Immunity
Active Immunity results from the production of antibodies by the immune system in response to the presence of an antigen.
- Natural: Infection with the actual disease.
- Artificial: Vaccination (Live attenuated, Inactivated, Subunit, Toxoid, mRNA).
- Duration: Usually long-term (years to lifelong).
- Onset: Takes weeks to develop protection.
Vaccine Classifications & Contraindications
For the MCCQE1, you must distinguish between Live Attenuated and Inactivated vaccines, as this dictates contraindications (pregnancy, immunocompromised states).
Live Attenuated Vaccines
These contain weakened forms of the organism. They induce a strong, long-lasting immune response but pose risks to specific groups.
Common Live Vaccines:
- Measles, Mumps, Rubella (MMR)
- Varicella (Chickenpox)
- Zoster (Live version - Zostavax; note: Recombinant Shingrix is preferred in Canada)
- Yellow Fever
- Rotavirus (Oral)
- Influenza (Intranasal only - rarely used in adults)
- BCG
- Oral Polio (Sabin) - Not used in Canada (we use IPV)
- Oral Typhoid
💡 Canadian Mnemonic: “MR. VOY”
MMR
Rotavirus
Varicella
Oral Typhoid/Polio
Yellow Fever
CONTRAINDICATED in Pregnancy and Severe Immunocompromise.
Inactivated Vaccines
Safe for immunocompromised patients and usually safe in pregnancy (though timing matters).
- Examples: Influenza (IM), Pneumococcal, Meningococcal, Hepatitis A & B, HPV, Tdap, IPV (Inactivated Polio).
Routine Canadian Immunization Schedule
While you do not need to memorize every provincial nuance, you must know the standard timing for primary series and boosters.
Infant and Childhood Schedule
| Age | Vaccines (Abbreviations) | Key Notes for MCCQE1 |
|---|---|---|
| Birth | Hep B | Only in some provinces (e.g., BC) or if high-risk. |
| 2 Months | DTaP-IPV-Hib-HB, Pneumo-C-15, Rotavirus | ”6-in-1” vaccine is standard. |
| 4 Months | DTaP-IPV-Hib-HB, Pneumo-C-15, Rotavirus | Second dose. |
| 6 Months | DTaP-IPV-Hib-HB, Rotavirus | Third dose. Influenza starts here (annual). |
| 12 Months | MMR-V, Pneumo-C-15, Men-C-C | First live vaccines given at 1 year. |
| 18 Months | DTaP-IPV-Hib, MMR-V (2nd dose) | 2nd dose of Varicella is crucial. |
| 4-6 Years | DTaP-IPV, MMR-V | Pre-school booster. |
| Grade 6-9 | HPV, Hep B, Men-C-ACWY | School-based programs vary by province. |
| 14-16 Years | Tdap | Adolescent booster. |
Note: Rotavirus vaccine has a strict age limit. The first dose should not be given after 15 weeks, and the series must be completed by 8 months to reduce the risk of intussusception.
Adult Immunization
- Tetanus/Diphtheria (Td): Every 10 years.
- Pertussis (Tdap): One dose in adulthood (routinely given during every pregnancy).
- Herpes Zoster (Shingles): Recombinant zoster vaccine (RZV/Shingrix) recommended for age ≥50 years (2 doses, 2-6 months apart).
- Pneumococcal: Pneu-C-20 (Prevnar 20) for age ≥65 years or high-risk adults.
- Influenza: Annual for everyone ≥6 months.
Special Populations & Canadian Guidelines
This section is extremely high-yield for clinical reasoning questions on the MCCQE1.
1. Pregnancy
- Recommended:
- Tdap: Every pregnancy, ideally between 27-32 weeks gestation (to transfer antibodies to fetus).
- Influenza (Inactivated): Any trimester during flu season.
- COVID-19: Recommended.
- Contraindicated: All live vaccines (MMR, Varicella).
- Rubella: Screen prenatal. If non-immune, vaccinate post-partum (before discharge).
- Varicella: If non-immune, vaccinate post-partum.
- Hepatitis B: Screen prenatal. If HBsAg positive, infant gets HBIG + Vaccine at birth.
2. Asplenia (Anatomic or Functional)
Patients with sickle cell disease or post-splenectomy are at risk for encapsulated organisms.
- Required Vaccines:
- Pneumococcal
- Meningococcal (ACWY and B)
- Haemophilus influenzae type b (Hib)
- Annual Influenza
- Timing: Elective splenectomy? Vaccinate 2 weeks before surgery. Emergency splenectomy? Vaccinate 2 weeks after surgery.
3. Immunocompromised Hosts
- Generally avoid live vaccines.
- Exceptions:
- HIV: MMR and Varicella can be considered if CD4 count is ≥200/µL and % ≥15%.
- SCT (Stem Cell Transplant): Revaccination required starting 6-12 months post-transplant as they lose prior immunity.
Post-Exposure Prophylaxis (PEP) Guidelines
Tetanus Wound Management
This is a classic MCCQE1 data interpretation task.
| Vaccination History | Clean, Minor Wound | All Other Wounds (Dirty) |
|---|---|---|
| Unknown or <3 doses | Give Td/Tdap No TIG | Give Td/Tdap Give TIG (opposite limb) |
| ≥3 doses | No vaccine (Unless >10 years since last dose) | No vaccine (Unless >5 years since last dose) |
Other PEP Scenarios
- Varicella:
- Exposure in non-immune pregnant woman or immunocompromised: VarIG (Varicella Immunoglobulin) within 96 hours (up to 10 days).
- Exposure in non-immune healthy adult: Varicella Vaccine within 3-5 days.
- Hepatitis B:
- Percutaneous exposure (needlestick) in non-immune: HBIG + Vaccine.
- Rabies:
- Category III exposure (bite/scratch with blood): RIG (infiltrate wound) + Vaccine (Days 0, 3, 7, 14).
Addressing Vaccine Hesitancy
The MCCQE1 tests your ability to communicate effectively. Do not be dismissive. Use the motivational interviewing approach.
Step 1: Ask and Listen
“What specific concerns do you have about the vaccines?” Listen without interrupting.
Step 2: Acknowledge and Validate
“I understand you are worried about the safety of the MMR vaccine because of what you read online. It is normal to want the best for your child.”
Step 3: Advise and Inform
Provide scientific evidence in accessible language. “Large studies in Canada and globally have shown no link between autism and vaccines. The risk of measles, however, includes…”
Step 4: Plan
If they refuse, keep the door open. “I respect your decision. Let’s discuss this again at the next visit.” Document the refusal.
Key Points to Remember for MCCQE1
- Anaphylaxis: The only absolute contraindication to a subsequent dose of the same vaccine.
- Egg Allergy: No longer a contraindication for MMR or Influenza vaccines (inactivated). Observe for 15-30 mins.
- Preterm Infants: Vaccinate according to chronological age, not corrected age. Do not reduce doses.
- Multiple Injections: Safe to give multiple vaccines at the same visit (different limbs).
- Live Vaccines Rule: Two live parenteral vaccines must be given on the same day OR separated by at least 4 weeks.
Sample Question
Clinical Scenario
A 28-year-old male presents to the emergency department after stepping on a rusty nail at a construction site. The wound is deep and contaminated with soil. He is alert and hemodynamically stable. He moved to Canada 3 years ago and is unsure of his immunization history. He thinks he received “some shots” as a child but has no documentation. He has no known allergies.
Which of the following is the most appropriate management?
Options
- A. Administer Tdap vaccine only
- B. Administer Tetanus Immune Globulin (TIG) only
- C. Administer Td vaccine and prescribe oral antibiotics
- D. Administer Tdap vaccine and Tetanus Immune Globulin (TIG)
- E. Order serum tetanus antitoxin levels before treatment
Explanation
The correct answer is:
- D. Administer Tdap vaccine and Tetanus Immune Globulin (TIG)
Detailed Analysis: This patient has a “dirty” wound (contaminated with soil, deep puncture) and an uncertain immunization history. According to Canadian guidelines (CIG), a patient with an unknown history or fewer than 3 doses of tetanus-containing vaccine presenting with a dirty wound requires both passive immunity (TIG) for immediate protection and active immunity (Vaccine) to start the series.
- Why Tdap? In adults with unknown history, the first dose should preferably be Tdap (to cover Pertussis) followed by Td for completion of the series.
- Why TIG? The wound is dirty and the patient is not fully immunized; the vaccine takes weeks to produce antibodies. TIG provides immediate neutralization of the toxin.
- Option A: Incorrect. Vaccine alone is insufficient for a dirty wound in a non-immune patient.
- Option B: Incorrect. TIG provides temporary protection but does not induce active immunity. He needs the vaccine series started.
- Option C: Incorrect. Antibiotics are not a substitute for prophylaxis against tetanus toxin.
- Option E: Incorrect. Wound management should not be delayed for serology.
References
- Public Health Agency of Canada. Canadian Immunization Guide. Evergreen edition. https://www.canada.ca/en/public-health/services/canadian-immunization-guide.html
- Canadian Paediatric Society. Immunization Competencies for Health Professionals.
- Medical Council of Canada. MCCQE Part I Objectives: Population Health and Infectious Diseases.
- National Advisory Committee on Immunization (NACI). Statements and Publications.