From 1995 to 2015, nearly 40% of all reported cases of typhoid fever in the United States occurred in children, highlighting the need to improve coverage with currently licensed vaccines and introduce an effective pretravel typhoid vaccine for children younger than 2 years of age, according to study results published in Clinical Infectious Diseases.
Researchers reviewed typhoid cases reported to the National Typhoid and Paratyphoid Fever Surveillance to characterize pediatric typhoid fever infections diagnosed in the United States and described antimicrobial resistance patterns using Typhi isolates tested by the National Antimicrobial Resistance Monitoring System.
Of the 5131 typhoid fever cases included in the study, 38.8% (n=1992) occurred in people younger than 18 years of age, where 210 children were 6-23 month of age. Compared with adult cases, pediatric cases were more frequently associated with a chronic carrier (7.0% vs 2.2%; P <.001) or an outbreak (9.2% vs 5.3%; P <.001), and more likely to be hospitalized (81.0% vs 73.9%; P <.001).
Of the 1992 pediatric patients, travel data was available for 1941. Of these, 83.2% (1616/1941) had traveled internationally within 30 days of illness onset, most frequently to Asia (84.5%). South Asia was the most common subregion (overall, 93.2%) with India, Pakistan, and Bangladesh being the most common countries visited. Although 88.8% (1435/1616) of children were eligible for vaccination, only 5.7% (57/998) received a typhoid vaccine, highlighting the need to promote vaccine coverage among eligible children with currently available vaccines.
Of the 2003 isolates from pediatric patients tested for antimicrobial susceptibility, 1216 (60.7%) were fluoroquinolone-nonsusceptible (FQ-NS), defined as having decreased susceptibility or resistance to ciprofloxacin or resistance to nalidixic acid. In addition, there were 320 (16%) multidrug-resistant (MDR) isolates, defined as resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole. No isolates were resistant to azithromycin or ceftriaxone.
FQ-NS and MDR isolates were more common in children than adults (16.0% vs 9.1% [P <.001] and 60.7% vs 53.9% [P <.001], respectively). In addition, travel to South Asia accounted for the largest proportion of travel-associated drug resistance for both FQ-NS and MDR isolates: 94.7% (709/748) of FQ-NS isolates and 83.7% (149/178) of MDR isolates.
Given that 81% (1544/1906) of children with typhoid were hospitalized, and “children aged 6 to 23 months old, currently ineligible for vaccination, were more likely to be hospitalized than older children,” a licensed typhoid conjugate vaccine “in the United States for children younger than 2 years old would provide an additional tool for ensuring typhoid protection for young travelers” and help prevent drug-resistant infections, the researchers concluded.
McAteer J, Derado G, Hughes M, et al. Typhoid fever in the US pediatric population, 1999–2015: opportunities for improvement. Clin Infect Dis. Published online July 7, 2020. doi:10.1093/cid/ciaa914