A 28-year-old woman presents to her physician for follow-up. She was found to be HIV-positive 9 months ago. Currently she is on ART with lamivudine, tenofovir, and efavirenz. She has no complaints and only reports a history of mild respiratory infection since the last follow-up. She is also allergic to egg whites. Her vital signs are as follows: the blood pressure is 120/75 mm Hg, the heart rate is 73/min, the respiratory rate is 13/min, and the temperature is 36.7°C (98.0°F). She weighs 68 kg (150 lb), and there is no change in her weight since the last visit. On physical examination, she appears to be pale, her lymph nodes are not enlarged, her heart sounds are normal, and her lungs are clear to auscultation. Her total blood count shows the following findings: Erythrocytes 3.2 x 106/mm3 Hematocrit 36% Hgb 10 g/dL Total leukocyte count 3,900/mm3 Neutrophils 66% Lymphocytes 24% Eosinophils 3% Basophils 1% Monocytes 7% Platelet count 280,000/mm3 Her CD4+ cell count is 430 cells/µL. The patient tells you she would like to get an influenza vaccination as flu season is coming. Which of the following statements is true regarding influenza vaccination in this patient?

The patient can receive approved recombinant or inactivated influenza vaccines, with egg-free formulations preferred due to her egg allergy.

As long as the patient is anemic, she should not be vaccinated.

Influenza vaccination is contraindicated in HIV-positive patients because of the serious complications they can cause in immunocompromised people.

Inactivated or recombinant influenza vaccines fail to induce a sufficient immune response in patients with CD4+ cell counts under 500 cells/µL.

Nasal-spray influenza vaccine is the best option for vaccination in this patient.

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 6-year-old girl presents to the clinic for a general checkup before her last scheduled DTaP vaccination. Her mother is concerned about mild swelling and redness at the site of injection after her daughter’s previous DTaP administration. The patient has mild spastic cerebral palsy. She was diagnosed with epilepsy at the age of 5, and it is well-controlled with levetiracetam. She is allergic to penicillin. Currently, she complains of malaise and mild breathlessness. The mother noted that her daughter has been sluggish for the last 3 days. Her vital signs are as follows: the blood pressure is 100/60 mm Hg, the heart rate is 90/min, the respiratory rate is 22/min, and the temperature is 38.8°C (101.8°F). On physical examination, the patient has slightly enlarged submandibular lymph nodes bilaterally and oropharyngeal erythema. On auscultation, there are diminished vesicular breath sounds with a few respiratory crackles over the lower lobe of the left lung. Which of the following factors requires delaying the patient’s vaccination?

Mild swelling and redness at the site of injection after the previous vaccine administration

A 24-year-old newly immigrated mother arrives to the clinic to discuss breastfeeding options for her newborn child. Her medical history is unclear as she has recently arrived from Sub-Saharan Africa. You tell her that unfortunately she will not be able to breastfeed until further testing is performed. Which of the following infections is an absolute contraindication to breastfeeding?

Human Immunodeficiency Virus (HIV)

A 12-month-old boy presents for a routine checkup. The patient immigrated from the Philippines with his parents a few months ago. No prior immunization records are available. The patient’s mother claims that he had a series of shots at 6 months of age which gave him a severe allergic reaction with swelling of the tongue and the face. She also remembers that he had the same reaction when she introduced solid foods to his diet, including carrots, eggs, and bananas. Which of the following vaccinations are not recommended for this patient?

Intramuscular influenza vaccine

Measles, mumps, and rubella (MMR) vaccine

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 34-year-old man comes to the physician for a routine health maintenance examination. He was diagnosed with HIV 8 years ago. He is currently receiving triple antiretroviral therapy. He is sexually active and uses condoms consistently. He is planning a trip to Thailand with his partner to celebrate his 35th birthday in 6 weeks. His last tetanus and diphtheria booster was given 4 years ago. He received three vaccinations against hepatitis B 5 years ago. He had chickenpox as a child. Other immunization records are unknown. Vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Leukocyte count shows 8,700/mm3, and CD4+ T-lymphocyte count is 480 cells/mm3 (Normal ≥ 500); anti-HBs is 150 mIU/mL. Which of the following recommendations is most appropriate at this time?

Tetanus, diphtheria, pertussis vaccine (Tdap)

Measles, mumps, rubella vaccine

Vaccine contraindications and precautions for USMLE Step 1: High-Yield Pediatrics Lessons

Definitions - Stop vs. Slow Down

Contraindication (STOP 🛑): A condition that severely ↑ the risk of a serious adverse reaction. The vaccine must not be given.
- Example: Anaphylaxis to a previous dose.
Precaution (SLOW DOWN ⚠️): A condition that may ↑ the risk of an adverse event or ↓ vaccine efficacy. Vaccination should generally be deferred; risk vs. benefit analysis is key.
- Example: Moderate-to-severe acute illness (with or without fever).

⭐ A severe allergic reaction (e.g., anaphylaxis) after a previous dose or to a vaccine component is a true contraindication to subsequent doses.

Live Vaccines - Handle with Care

📌 Mnemonic: BOY, This Real Virus is Live

BCG
OPV (Oral Polio)
Yellow Fever
Typhoid (Oral Ty21a)
Rotavirus
Varicella
Influenza (intranasal)
MMR (Measles, Mumps, Rubella)

⚠️ Absolute Contraindications

Pregnancy: Teratogenic risk. Avoid conception for 4 weeks post-vaccination.
Severe Immunodeficiency: Risk of disseminated disease.
- Primary Immunodeficiencies: SCID, CVID, DiGeorge syndrome.
- Leukemia, Lymphoma, generalized malignancy.
- Chemotherapy or radiation therapy (wait 3 months after stopping).
- High-dose corticosteroids:
  - ≥2 mg/kg/day or ≥20 mg/day if taken for >14 days.
  - Wait 1 month after discontinuation.

⭐ In HIV-infected children, MMR & Varicella vaccines are NOT contraindicated if CD4 count is adequate (CD4% ≥15% for age <5 yrs; CD4 count ≥200/μL for age >5 yrs).

💡 Precautions (Weigh Risk vs. Benefit)

Recent Blood/Antibody Products:
- Antibodies can neutralize the vaccine virus.
- Defer MMR/Varicella for 3-11 months depending on the product received.
Moderate or Severe Acute Illness: Defer until recovery.
Household Contacts of Immunocompromised:
- MMR & Varicella are safe.
- Rotavirus: Theoretical risk of transmission; counsel on hand hygiene.
- OPV: Not used in developed countries due to VAPP risk.

Specific Vaccines - Tricky Scenarios

BCG: No scar post-vaccination? → Revaccinate if Mantoux test is < 5 mm. Give to asymptomatic HIV-positive infants.
Hepatitis B: Mother is HBsAg-positive? → Give vaccine + Hepatitis B Immunoglobulin (HBIG) at birth, at different sites.
OPV: Child vomits within 30 minutes? → Repeat the dose.
Measles: Outbreak situation? → Give an additional dose at 6-9 months. This does not replace the scheduled 9-month dose.
DTP: History of encephalopathy within 7 days of a previous dose? → Pertussis component is contraindicated. Use DT instead.

Hepatitis B Vaccine Management for HBV-Exposed Infants

⭐ Egg allergy is NOT a contraindication for the measles vaccine. The vaccine is prepared on a chick embryo fibroblast culture, not the egg itself.

High‑Yield Points - ⚡ Biggest Takeaways

Live vaccines are contraindicated in immunocompromised states and pregnancy.

Anaphylaxis to a prior dose or vaccine component is an absolute contraindication for all vaccines.

Encephalopathy within 7 days of a previous DTP/DTaP dose is a contraindication for further doses.

Egg allergy: Influenza and Yellow Fever vaccines require caution, but anaphylaxis is a contraindication.

Rotavirus vaccine is contraindicated in infants with a history of intussusception or SCID.

MMR & Varicella are contraindicated with neomycin anaphylaxis.

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