A 40-year-old pregnant woman, G4 P3, visits your office at week 30 of gestation. She is very excited about her pregnancy and wants to be the healthiest she can be in preparation for labor and for her baby. What vaccination should she receive at this visit?

Tetanus, diphtheria, and acellular pertussis (Tdap)

Measles, mumps, and rubella (MMR)

Live attenuated influenza vaccine

An 11-year-old boy is brought to his pediatrician by his parents for the routine Tdap immunization booster dose that is given during adolescence. Upon reviewing the patient’s medical records, the pediatrician notes that he was immunized according to CDC recommendations, with the exception that he received a catch-up Tdap immunization at the age of 8 years. When the pediatrician asks the boy’s parents about this delay, they inform the doctor that they immigrated to this country 3 years ago from Southeast Asia, where the child had not been immunized against diphtheria, tetanus, and pertussis. Therefore, he received a catch-up series at 8 years of age, which included the first dose of the Tdap vaccine. Which of the following options should the pediatrician choose to continue the boy’s immunization schedule?

A single dose of Tdap vaccine at 13 years of age

A single dose of Td vaccine at 18 years of age

A single dose of Td vaccine now

A single dose of Tdap vaccine now

A 4-month-old boy is brought to the physician by his parents for a well-child examination. He has cystic fibrosis diagnosed by newborn screening. His parents report frequent feedings and large-volume and greasy stools. His 4-year-old brother has autism. Current medications include bronchodilators, pancreatic enzyme supplements, and fat-soluble vitamins. He is at the 18th percentile for height and 15th percentile for weight. Scattered wheezes are heard throughout both lung fields. Examination shows a distended and tympanic abdomen with no tenderness or guarding. Which of the following is a contraindication for administering one or more routine vaccinations?

Fever of 38.2°C (100.7°F) following previous vaccinations

A 28-year-old woman gives birth to a 2.2 kg child while on vacation. The mother's medical records are faxed to the hospital and demonstrate the following on hepatitis panel: hepatitis B surface antigen (HbsAg) positive, anti-hepatitis B core antigen (anti-HbcAg) positive, hepatitis C RNA is detected, hepatitis C antibody is reactive. Which of the following should be administered to the patient's newborn child?

Hepatitis B vaccine, ledipasvir/sofosbuvir

Hepatitis B IVIG, hepatitis B vaccine and ledipasvir/sofosbuvir

Hepatitis B IVIG now, hepatitis B vaccine in one month

A 15-month-old girl is brought to her primary care physician for a follow-up visit to receive the 4th dose of her DTaP vaccine. She is up-to-date on her vaccinations. She received her 1st dose of MMR, 1st dose of varicella, 3rd dose of HiB, 4th dose of PCV13, and 3rd dose of polio vaccine 3 months ago. Thirteen days after receiving these vaccinations, the child developed a fever up to 40.5°C (104.9°F) and had one generalized seizure that lasted for 2 minutes. She was taken to the emergency department. The girl was sent home after workup for the seizure was unremarkable and her temperature subsided with acetaminophen therapy. She has not had any other symptoms since then. She has no history of serious illness and takes no medications. Her mother is concerned about receiving further vaccinations because she is afraid of the girl having more seizures. Her vital signs are within normal limits. Examination shows no abnormalities. Which of the following is the most appropriate recommendation at this time?

Administration of the DTaP vaccine as scheduled

Administration of the DTaP vaccine with valproic acid

Administration of a reduced-dose DTaP vaccine

Refrain from administration of the DTaP vaccine

Administration of the DTaP vaccine with prophylactic aspirin

A 19-year-old male arrives to student health for an annual check up. He is up to date on his infant and childhood vaccinations up to age 10. At age 12, he received a single dose of the tetanus, diphtheria, and acellular pertussis vaccine, and a quadrivalent meningococcal conjugate vaccine. A month ago, he received the influenza vaccine. The patient has no significant medical history. He takes over the counter ibuprofen for occasional headaches. He has a father with hypertension and hyperlipidemia, and his brother has asthma. He is sexually active with his current girlfriend. He denies tobacco use, illicit drug use, and recent or future travel. The patient’s temperature is 98°F (36.7°C), blood pressure is 118/78 mmHg, pulse is 70/min, and respirations are 14/min with an oxygen saturation of 99% O2 on room air. A physical examination is normal. What of the following is the best recommendation for vaccination?

Tetanus and reduced diphtheria toxoid booster

Childhood immunization schedule for USMLE Step 2 CK: High-Yield Microbiology Lessons

Vaccine Fundamentals - Live vs. Inactivated

Feature	Live Attenuated	Inactivated (Killed)
Immunity	Humoral & Cellular (long-lasting)	Mainly Humoral (shorter)
Boosters	Single dose often sufficient	Multiple boosters needed
Safety	Risk of reversion; ⚠️ Avoid in immunocompromised/pregnancy	No risk of infection
Stability	Less stable (requires cold chain)	More stable

⭐ Live vaccines generate a robust IgA response, mimicking natural infection, especially when given via mucosal routes (e.g., intranasal influenza, oral rotavirus).

Live Attenuated Vaccines: How They Work

Birth & Infancy (0-6 mo) - Tiny Shots, Big Shield

At Birth: Hepatitis B (1st dose).
2, 4, 6 Months: Core vaccination series.
- DTaP, PCV13, Hib, IPV (Inactivated Polio).
- Rotavirus (RV) - the only oral vaccine in this group.

📌 Mnemonic for 2, 4, 6 mo shots: "DR. HIP" (DTaP, Rotavirus, Hib, IPV, PCV13).

Childhood Immunization Schedule (Birth to 16 Years)

⭐ For an HBsAg-positive mother, give the infant Hepatitis B vaccine AND Hepatitis B Immune Globulin (HBIG) within 12 hours of birth.

Toddler Vaccines (12-18 mo) - MMR & Varicella Debut

MMR & Varicella (Live Attenuated):
- First dose for both at 12-15 months.
- Protects against Measles, Mumps, Rubella (MMR) & Chickenpox (VZV).
- Give same day or separate by ≥4 weeks.
- ⚠️ Contraindicated in severe immunodeficiency, pregnancy.
Hepatitis A (Inactivated):
- 2-dose series starting at 12 months, separated by 6-18 months.
DTaP, Hib, PCV13:
- Boosters often given in this window (12-18 mo).

⭐ A mild, non-contagious rash can appear 7-14 days after MMR or Varicella vaccination; this is a normal reaction, not an allergy.

2025 US Childhood Immunization Schedule (Birth-18 Years)

Preschool Boosters (4-6 yrs) - Kindergarten Ready

Final doses for four key vaccines before school entry, ensuring community protection. Typically administered together at the same visit.

DTaP (5th dose): Diphtheria, Tetanus, acellular Pertussis.
IPV (4th dose): Inactivated Poliovirus.
MMR (2nd dose): Measles, Mumps, Rubella.
Varicella (2nd dose): Chickenpox.

📌 Mnemonic: "Doctors In My Vicinity" (DTaP, IPV, MMR, Varicella).

⭐ High-Yield: MMR and Varicella are live attenuated vaccines. They can be given on the same day. If not, they must be separated by at least 28 days.

Adolescent Vaccines (11-18 yrs) - Teen Guard

Tdap Booster:
- Given once at age 11-12.
- Protects against Tetanus, Diphtheria, and acellular Pertussis.
HPV (Human Papillomavirus):
- Recommended at age 11-12 (can start at 9).
- 2 doses if series starts before age 15; 3 doses if started at age 15 or older.
Meningococcal Conjugate (MenACWY):
- First dose at 11-12 years.
- Booster dose at age 16.

⭐ High-Yield: The HPV vaccine is recommended for both males and females to prevent not only cervical cancer but also anal and oropharyngeal cancers.

2024 CDC Immunization Schedule for Children 7-18 Years

High‑Yield Points - ⚡ Biggest Takeaways

Live attenuated vaccines (MMR, varicella, rotavirus, intranasal flu) are generally contraindicated in pregnancy and severe immunodeficiency.

The HepB vaccine series is initiated at birth.

Key 2, 4, 6-month vaccines include DTaP, Hib, PCV13, Polio, and Rotavirus.

First doses of MMR and Varicella are administered at age 12-15 months.

Adolescents receive Tdap, HPV, and Meningococcal vaccines around age 11-12 years.

Egg allergy is not a contraindication for the MMR or most influenza vaccines.

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