Fever in unvaccinated children

An 11 month old male is brought into the ED by his mother with fever as high as 104.5° Fahrenheit (40.3 C) and vomiting for the last 12 hours.  He has made fewer-than-usual wet diapers today and has vomited after nearly every feeding.  He is not in day care.  He was born via uncomplicated spontaneous vaginal delivery at 39 weeks, was circumcised at birth, has no known medical problems, no medications or medication allergies, and has never had surgery.  When asked about his vaccination status, his mother states “Oh, we don’t do vaccines in my home.”

Vital signs are: Temperature 103.7° F (39.8 C)after 160 mg acetaminophen given in triage 20 minutes ago, weight 10.5 kg, heart rate 152, respiratory rate 34, blood pressure 74/52 and pulse oximetry of 98% on room air.

The child is moderately ill appearing, fussy but consolable.  He allows the physician to examine him when presented with Dora the Explorer on a tablet computer.  Physical exam is nonfocal.  He is treated with 2 mg ondansetron orally dissolving tablet and 100 mg ibuprofen, and responds by drinking 6 ounces of PediaLyte, wetting his diaper and falling asleep with temperature now 100.1° F (37.8 C) and heart rate 115.

Routine vaccination has had an astonishing public health impact.  Since the widespread adoption of H. influenzae type b and polyvalent S. pneumoniae vaccines, the incidence of occult bacteremia in well-appearing febrile children aged 3-36 months has decreased from roughly 5 percent to well under 1 percent (1).  Most clinical guidelines for care of the febrile child now allow for a much-less-aggressive evaluation strategy, predicated on the assumption that the child is fully immunized (2).  However, despite the well documented advantages of vaccination, there remains a not-insignificant minority of parents in the United States who prefer not to vaccinate their children, (for a wide variety of reasons that are beyond the scope of this posting) and there is limited current data regarding the appropriate management of those children.  It seems most reasonable, therefore, to use the evaluation and management guidelines of the pre-vaccine era (3).

Among “highly febrile” (temperature greater than 102.2° F or 39 C) unvaccinated children aged 3 to 36 months, the incidence of occult bacteremia is perhaps as high as 10 percent when the white blood cell count is greater than 15,000 (4,5), and response to antipyretic treatment is not reliable to rule out serious bacterial infectoin.  As such, a complete blood count and blood cultures (either for a WBC count greater than 15,000 or for all) are recommended in the evaluation of incompletely vaccinated children.  Furthermore, unsuspected (but radiographically evident) pneumonia is found in 20-40% of children with a white blood cell count greater than 20,000(6,7), so chest radiography should be considered in that subgroup.  Incidence of urinary tract infection is not significantly affected by vaccination against S. pneumoniae and H. influenzae type b, and consequently the existing guidelines for obtaining urinalysis and urine culture in highly febrile children should be observed (females under 24 months, circumcised males under 6 months and uncircumcised males under 12 months) (8).

Regarding CSF studies, the incidence of unsuspected meningitis in the well appearing incompletely vaccinated child aged 3-36 months is quite low (9).  Although some authors routinely performed lumbar puncture in all febrile infants under 12 months of age (4), this practice is not recommended as a routine part of the workup in the otherwise well appearing child.

That being said, meningitis is a common complication of untreated occult bacteremia, occurring secondarily in nearly 10 percent of children with bacteremia, but only 0.3 % of those empirically treated with ceftriaxone, 50 mg/kg (IM in the study though the IV route seems reasonable as well) (10).  As such, empiric treatment is recommended for those at high risk of occult bacteremia, with clindamycin as an alternative regimen for those allergic to cephalosporins.  Followup should be arranged within 24 hours, and if that is not assured, admission should be considered.

References – see note on #3

1. Craig JC, et al.  The accuracy of clinical symptoms and signs for the diagnosis of serious bacterial infection in young febrile children: prospective cohort study of 15 781 febrile illnesses.  BMJ. 2010;340:c1594

2. ACEP Clinical Policy for Children Younger Than Three Years Presenting to the Emergency Department With Fever. Ann Emerg Med. 2003;42:530-545.]

3. Allen CH.  Fever without a source in children 3 to 36 months of age. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2013.  As a side note, I started this article, then came across this really excellent UpToDate topic.  If I had just linked Dr. Allen’s topic under the initial case presentation, it would have saved me quite a bit of work)

4. Carroll WL, et al. Treatment of occult bacteremia: a prospective randomized clinical trial. Pediatrics. 1983;72(5):608.

5. Bass JW , et al Antimicrobial treatment of occult bacteremia: a multicenter cooperative study.  Pediatr Infect Dis J. 1993;12(6):466.

6. Bachur R, et al. Occult pneumonias: empiric chest radiographs in febrile children with leukocytosis.  Ann Emerg Med. 1999;33(2):166

7. Brauner M , et al. Extreme leucocytosis and the risk of serious bacterial infections in febrile children.  Arch Dis Child. 2010;95(3):209.

8. Shaw KN, et al.  Prevalence of urinary tract infection in febrile young children in the emergency department. Pediatrics. 1998;102(2):e16

9. McCarthy PL. Acute infectious illness in children. Compr Ther. 1988;14(3):51

10. Baraff LJ, et al. Effect of antibiotic therapy and etiologic microorganism on the risk of bacterial meningitis in children with occult bacteremia.  Pediatrics. 1993;92(1):140.

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