A 29-year-old man comes to the physician for a routine health maintenance examination. He feels well. He works as a nurse at a local hospital in the city. Three days ago, he had a needlestick injury from a patient whose serology is positive for hepatitis B. He completed the 3-dose regimen of the hepatitis B vaccine 2 years ago. His other immunizations are up-to-date. He appears healthy. Physical examination shows no abnormalities. He is concerned about his risk of being infected with hepatitis B following his needlestick injury. Serum studies show negative results for hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis C antibody. Which of the following is the most appropriate next step in management?

Administer hepatitis B immunoglobulin and 3-dose regimen of hepatitis B vaccine

Revaccinate with 3-dose regimen of hepatitis B vaccine

Revaccinate with two doses of hepatitis B vaccine

Administer hepatitis B immunoglobulin

Administer hepatitis B immunoglobulin and single dose hepatitis B vaccine

An 18-year-old girl is brought to the emergency department because of a 1-day history of severe headache with photophobia and diffuse myalgias. She is a college student and lives in a dormitory in a large urban area. She has not traveled recently. On arrival, she is lethargic. Her temperature is 39.3°C (102.7°F), pulse is 120/min, and blood pressure is 88/58 mm Hg. Examination shows scattered petechiae and ecchymoses on the trunk and lower extremities. There is decreased range of motion of the neck. Cerebrospinal fluid analysis shows a cell count of 1,600/μL (80% neutrophils) and a lactate concentration of 5.1 mmol/L. Which of the following is most likely to have prevented this patient's condition?

Polysaccharide conjugate vaccine

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 9-month-old boy is brought to a pediatrician by his parents for routine immunization. The parents say they have recently immigrated to the United States from a developing country, where the infant was receiving immunizations as per the national immunization schedule for that country. The pediatrician prepares a plan for the infant’s immunizations as per standard US guidelines. Looking at the plan, the parents ask why the infant needs to be vaccinated with injectable polio vaccine, as he had already received an oral polio vaccine back in their home country. The pediatrician explains to them that, as per the recommended immunization schedule for children and adolescents in the United States, it is important to complete the schedule of immunizations using the injectable polio vaccine (IPV). He also mentions that IPV is considered safer than OPV, and IPV has some distinct advantages over OPV. Which of the following statements best explains the advantage of IPV over OPV to which the pediatrician is referring?

IPV is known to produce higher titers of serum IgG antibodies than OPV

IPV is known to produce higher titers of mucosal IgG antibodies than OPV

IPV is known to produce virus-specific CD4+ T cells that produce interleukins and interferons to control polio viruses

IPV is known to produce higher titers of mucosal IgA antibodies than OPV

IPV is known to produce virus-specific CD8+ T cells that directly kill polio-infected cells

A 12-year-old boy, otherwise healthy, presents with frequent nosebleeds and lower extremity bruising. His mother reports that his symptoms started about 2 weeks ago and have not improved. The patient received the Tdap vaccine 2 weeks ago. He has no current medications. The review of systems is significant for the patient having a stomach ache after winning a hamburger eating competition 2 weeks ago. The vital signs include: temperature 37.0°C (98.6°F), blood pressure 110/75 mm Hg, pulse 95/min, respirations 15/min, and oxygen saturation 99% on room air. On physical exam, the patient is alert and cooperative. The cardiac exam is normal. The lungs are clear to auscultation bilaterally. The lower extremities findings are shown in the image. Laboratory results are pending. Which of the following best describes the pathogenesis of this patient’s condition?

IgG autoantibodies against platelet glycoproteins

Shiga-toxin mediated damage to vascular endothelium, resulting in microthrombi formation

Systemic activation of clotting cascade resulting in platelet and coagulation factor consumption

Deposition of IgA immune complexes

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

Vaccine adverse events for USMLE Step 1: High-Yield Pediatrics Lessons

AEFI Classification - The Reaction Spectrum

Vaccine product-related: Caused or precipitated by a vaccine's inherent properties.
Vaccine quality defect-related: Due to one or more quality defects of the vaccine product.
Immunization error-related: Caused by inappropriate handling, prescribing, or administration.
Immunization anxiety-related: Arising from anxiety about the immunization.
Coincidental event: Caused by something other than the vaccine, error, or anxiety.

⭐ Programmatic errors (immunization error-related reactions) are the most common and most preventable cause of AEFIs.

Common AEFIs - Fever, Owies & Lumps

Fever
- Most common systemic AEFI, esp. after DTP & Measles vaccines.
- Management: Paracetamol (10-15 mg/kg/dose).
Injection Site Reactions (Pain, Swelling, Redness)
- Most common local AEFI.
- Management: Cold compress. Usually resolves in 1-3 days.
- Sterile Abscess: Common with DPT, DT, TT. Indurated, painless swelling. No I&D needed.
- BCG Lymphadenitis: Non-suppurative resolves spontaneously.

⭐ Suppurative BCG lymphadenitis should NOT be excised; needle aspiration is preferred. Antitubercular therapy is generally reserved for extra-axillary or disseminated disease.

Infant thigh with post-vaccination swelling and redness

Severe AEFIs - Rare But Real Risks

Anaphylaxis: Acute, multi-system allergic reaction. Onset within 30 minutes.
- Management: IM Adrenaline (0.01 mg/kg, 1:1000 solution), max 0.5 mg.
Intussusception: Telescoping of the bowel, causing obstruction.
- Small ↑ risk with Rotavirus vaccines (RV1, RV5).
- Presents as colicky pain, vomiting, and red currant jelly stool.
Thrombocytopenic Purpura (ITP):
- Associated with MMR vaccine. Onset 15-35 days post-vaccination.
Hypotonic-Hyporesponsive Episode (HHE):
- Linked to Pertussis vaccine (DTwP > DTaP).
- Sudden pallor, limpness, ↓ responsiveness. Self-resolving.
Vaccine-Associated Paralytic Poliomyelitis (VAPP):
- Caused by live Oral Polio Vaccine (OPV). Risk: ~1 in 2.7 million doses.
- Reason for global shift to Inactivated Polio Vaccine (IPV).
Disseminated BCG Infection (BCG-osis):
- Occurs in infants with underlying immunodeficiency (e.g., SCID).

⭐ The highest risk of intussusception after the rotavirus vaccine is within the first 7 days following the first dose.

Ultrasound: Intussusception with target sign

AEFI Surveillance in India - Reporting for Duty

AEFI: Adverse Event Following Immunization. Any untoward medical occurrence post-immunization, which does not necessarily have a causal relationship with the vaccine.
Reporting: Mandatory for all healthcare workers. Done via SAFEVAC (Surveillance and Action for Events Following Vaccination) portal.

⭐ All serious AEFIs (resulting in death, hospitalization, disability, or cluster) must be reported to the District Immunization Officer (DIO) within 24 hours.

High‑Yield Points - ⚡ Biggest Takeaways

Most common AEFI is pain at the injection site; most common systemic symptom is fever.

Fever is most common after the whole-cell Pertussis (wP) vaccine.

Seizures are most linked to the wP component of the DPT vaccine.

Anaphylaxis, the most severe reaction, occurs within 30 minutes of vaccination.

Brachial neuritis is classically associated with the Tetanus toxoid.

MMR vaccine is linked to thrombocytopenia and aseptic meningitis.

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