This episode of PEM Currents: The Pediatric Emergency Medicine Podcast focuses on the approach to unvaccinated or undervaccinated children aged 3–36 months presenting to the ED with fever. Host Brad Sobolewski reviews differences in immune response, risk for serious and invasive bacterial infections, and outlines evaluation strategies including labs, imaging, and empiric antibiotics. He highlights data showing increased interventions in this population and calls for local guideline development. The episode emphasizes thoughtful, individualized care in the context of rising vaccine hesitancy and declining immunization rates.

Learning Objectives

• Compare the clinical presentation of bacterial infections in unvaccinated and undervaccinated children versus fully immunized children in the Emergency Department





• Assess the need for empiric antibiotics and diagnostic testing in an unvaccinated or undervaccinated child presenting with fever without source

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<figure class="wp-block-audio"><figcaption class="wp-element-caption">The Unvaccinated Child With Fever – Brad Sobolewski – PEM Currents: The Pediatric Emergency Medicine Podcast</figcaption></figure>



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References

Curtis M, Kanis J, Wagers B, et al. Immunization status and the management of febrile children in the pediatric emergency department: what are we doing? Pediatr Emerg Care. 2023;39(1):1-5. doi:10.1097/PEC.0000000000002864

Finkel L, Ospina-Jimenez C, Byers M, Eilbert W. Fever without source in unvaccinated children aged 3 to 24 months: what workup is recommended? Pediatr Emerg Care. 2021;37(12):e882-e885. doi:10.1097/PEC.0000000000002249

Herz AM, Greenhow TL, Alcantara J, et al. Changing epidemiology of outpatient bacteremia in 3- to 36-month-old children after the introduction of the heptavalent-conjugated pneumococcal vaccine. Pediatr Infect Dis J. 2006;25(4):293-300. doi:10.1097/01.inf.0000207485.39112.bf

Kaufman J, Fitzpatrick P, Tosif S, et al. Faster clean catch urine collection (Quick-Wee method) from infants: randomised controlled trial. BMJ. 2017;357:j1341. doi:10.1136/bmj.j1341

Kuppermann N, Fleisher GR, Jaffe DM. Predictors of occult pneumococcal bacteremia in young febrile children. Ann Emerg Med. 1998;31(6):679-687. doi:10.1016/S0196-0644(98)70225-2

Rutman MS, Bachur R, Harper MB. Radiographic pneumonia in young, highly febrile children with leukocytosis before and after universal conjugate pneumococcal vaccination. Pediatr Emerg Care. 2009;25(1):1-7. doi:10.1097/PEC.0b013e318191dab2

Trippella G, Galli L, De Martino M, Lisi C, Chiappini E. Procalcitonin performance in detecting serious and invasive bacterial infections in children with fever without apparent source: a systematic review and meta-analysis. Expert Rev Anti Infect Ther. 2017;15(11):1041-1057. doi:10.1080/14787210.2017.1400907

Van den Bruel A, Thompson MJ, Haj-Hassan T, et al. Diagnostic value of laboratory tests in identifying serious infections in febrile children: systematic review. BMJ. 2011;342:d3082. doi:10.1136/bmj.d3082

Transcript

Note: This transcript was partially completed with the use of the Descript AI

 Welcome to PEM Currents: The Pediatric Emergency Medicine P odcast. As always, I’m your host, Brad Sobolewski, and this episode is gonna focus on a challenging yet. Unfortunately, timely clinical question, what do we do with the UN or under vaccinated child who presents to the emergency department with fever? So what are we gonna go over in this episode?

Well, we’re gonna compare the clinical presentation of bacterial infections in unvaccinated and unvaccinated children versus fully immunized children in the emergency department, and we will assess the need for empiric antibiotics and diagnostic testing in this challenging population. Now, before you listen to this episode, I will presume that you are all familiar with the recommended child and adolescent immunization schedule for children ages 18 and younger in the United States or wherever you live.

So I’ll pause for a moment so that you can review that. Great. Welcome back, and there’s a few definitions that I will use. Unvaccinated or unm. Immunized means that you have no vaccines. Unvaccinated or under immunized means that you have some but not all of your vaccines, and you should always verify vaccine status via history EMR records and state registries.

So I think the first important question to answer is, when is a child immunocompetent? And honestly, competency is sort of on a sliding scale, and a child is immunocompetent if they have a normally functioning immune system capable of mounting an effective response to infections. So this means you have intact, innate and adaptive immunity with functioning neutrophils, macrophages, T cells, and B cells.

You don’t have. Severe combined immunodeficiency like a primary immunodeficiency or a secondary immunodeficiency. You’re on chemo or you’re severely malnourished. Immunocompetent kids respond to vaccines completely immunized, so greater than two doses of PCV and HIB should be immunocompetent against those bugs.

Unvaccinated or under vaccinated children are functionally immunocompromised in specific clinical scenarios such as fever without source. And it can be hard to figure out what immuno competency by disease and vaccine status really means. And so I do encourage you to be familiar with some of the information provided by the CDC as long as it’s still online.

So how common is it for children to be unvaccinated in the United States? Unfortunately. It’s getting more common. So as of the 2023-24 school year, about 3.3% of US kindergartners had an exemption from one or more required vaccines. That data is up versus 2022. 2023 translates to about 80,000 kids in the United States, and vaccination coverage varies across states.

So in the 2023-24 school year. MMR coverage was 79.6% in Idaho, and 98.3% in wild, wonderful West Virginia. 14 states reported exemption rates greater than 5% and in generally 95% vaccination rate for diseases needed for herd immunity. And we often wonder is the question of, well, is your kid’s vaccines up to date?

A good enough question, and let’s be honest, many of us just rely on adult caregivers to give us this information. Is your kid up to date on shots? Yeah, sure. I’ve had a few where up to date meant we were up to date in our decision to stop vaccinating them three years ago. EMR confirmation and state records are better and all 50 states, district of Columbia and some US territories do have immunization information systems.

And I’d encourage you to be familiar with and sign up for accounts on all of the different states that you work in. So for me, that’s Ohio, Kentucky, and Indiana. How often do we see UN or under vaccinated kids in the ed? And unsurprisingly, this number is not known. I asked some ID experts and we haven’t broadly assessed our rate, and we could do this, but it would take really a manual query of state vaccine records for any patient that doesn’t have vaccine status in the EMR.

And it would be timely and laborious though. Interesting. In Indiana, Curtis et al did a retrospective review of almost 800 well-appearing febrile children three to 36 months throughout 2019, presenting in one Indiana pediatric emergency department, and they were really looking at vaccine status. They excluded children with complex chronic illnesses like sickle cell disease, congenital heart disease, immunodeficiency, trach vent, et cetera, and they also excluded kids with an ill appearance or hemodynamic instability during that encounter.

They learned that 91.5% of their patients were fully vaccinated, five and a half percent were under vaccinated, and 3% were unvaccinated. Does that data match what you’ve seen and Yes, we don’t know the true scope of the problem. I. But I think perhaps a more important question is whether or not unvaccinated or unvaccinated children are more at risk for non-vaccine preventable illnesses.

Clearly they’re at risk for vaccine preventable illnesses ’cause they don’t have the vaccine. And so in this episode, I’m gonna focus mainly on children three to 36 months of age with fever for less than five days. And I will say that the approach to an unvaccinated febrile child may differ from fully immunized children due to an increased risk of occult bacteremia and invasive bacterial infections.

The child’s immune system matures both with and without vaccines. Maternal immunity wanes by about three to six months until 36 months to maybe five years. The adaptive immune system is still developing. And kids are less capable of mounting an effective response to encapsulated bacteria like streptococcus pneumonia.

Haemophilus influenza type B RIA