A 10-week-old boy is brought to the office for a follow-up visit. As part of his routine immunization schedule, the patient received the first dose of the Haemophilus influenzae type b (Hib) conjugate vaccine when he was 8 weeks old. However, following vaccine administration, he developed anaphylaxis, requiring epinephrine administration and hospitalization. As a result, the decision was made not to administer additional doses of the Hib vaccine. The patient was born full-term by uncomplicated vaginal delivery and has otherwise been healthy. Physical examination is unremarkable. His older brother has completed the full vaccination course. This patient is at highest risk of which of the following infections compared to his brother?

Question

A 10-week-old boy is brought to the office for a follow-up visit.  As part of his routine immunization schedule, the patient received the first dose of the Haemophilus influenzae type b (Hib) conjugate vaccine when he was 8 weeks old.  However, following vaccine administration, he developed anaphylaxis, requiring epinephrine administration and hospitalization.  As a result, the decision was made not to administer additional doses of the Hib vaccine.  The patient was born full-term by uncomplicated vaginal delivery and has otherwise been healthy.  Physical examination is unremarkable.  His older brother has completed the full vaccination course.  This patient is at highest risk of which of the following infections compared to his brother?

Quizplus · Accepted Answer

11ec160b_3844_d8b0_9249_0db1c06dfd6e_MD0001_00 Haemophilus influenzae is a gram-negative coccobacillus that can be either encapsulated (serotypes a-f) or unencapsulated (nontypeable). H influenzae type b (Hib) is the most invasive strain due to its polyribosylribitol phosphate (PRP) capsule, which inhibits complement-mediated phagocytosis and allows it to invade tissues and survive in the bloodstream. During the first months of life, transient immunity to Hib is accomplished by IgG antibodies acquired transplacentally from the mother while in utero. The Hib vaccine is administered beginning at age 2 months to provide continued immunity. The immunization is composed of PRP conjugated with a protein toxoid (eg, tetanus, diphtheria), which induces a T cell-dependent immune response. The production of opsonizing anticapsular antibodies by B-lymphocytes allows for efficient phagocytosis of the bacterium. Without the protection from the vaccine, this child is at risk for invasive disease caused by Hib, such as meningitis, bacteremia, pneumonia, and epiglottitis. (Choice A) Bronchiolitis is a lower respiratory infection that is almost always viral in etiology. Respiratory syncytial virus, rhinovirus, influenza, and parainfluenza are commonly implicated, but not H influenzae. (Choices B, D, and E) Most causes of bacterial conjunctivitis, acute otitis media, and sinusitis in childhood are due to Streptococcus pneumoniae, nontypeable H influenzae, and Moraxella catarrhalis. The Hib vaccine (which has no effect on nontypeable H influenzae) will not protect a child from these infections. Educational objective: The Haemophilus influenzae type b (Hib) vaccine induces anticapsular antibodies that facilitate complement-mediated phagocytosis of the bacterium. The vaccination series has drastically reduced the incidence of invasive disease caused by Hib, such as meningitis, bacteremia, pneumonia, and epiglottitis. __________ References: Pediatric invasive Haemophilus influenzae infections in Israel in the era of Haemophilus influenzae type b vaccine: a nationwide prospective study. (http://www.ncbi.nlm.nih.gov/pubmed/24445822)

A 10-Week-Old Boy Is Brought to the Office for a Follow-Up