Study: Ear infection profile shows change after pneumococcal vaccine introduction

Ear infections in young children have declined over the past decade since pneumococcal conjugate vaccines were introduced, and though infections from Streptococcus pneumoniae—the main cause of such infections—have dropped, other pathogens have stepped in as the main sources, researchers reported yesterday.

The findings, from a longitudinal study published yesterday in an early online issue of Pediatrics, provide one of the first glimpses of the epidemiology of acute otitis media (AOM) since the 1980s, before pneumococcal conjugate 7 and 13 vaccines were introduced. Since then, experts have tightened the clinical definition of and changed treatment guidance for AOM, the most common condition treated with antibiotics, a concern given rising antibiotic resistance levels.

According to American Academy of Pediatrics (AAP) estimates, more than 5 million AOM infections occur each year in US children, resulting in 30 million doctor visits and 10 million antibiotic prescriptions.

Bacterial patterns changed, but not risk factors

A team followed 615 children who were seen between 2006 and 2016 at a research-based pediatrics practice in Rochester, NY, in their first 3 years of life. The researchers used the AAP's current strict AOM definition.  They confirmed all infections with tympanocentesis and bacterial culture of middle-ear fluid, which they acknowledged as both a strength and a weakness of the study. They emphasized that the procedure has been shown to reduce pain, recurrence, and the need for tympanostomy tubes.

By age 1, 23% of the children had experienced one or more AOM episodes and 3.6% had had three or more infections. By age 3, about 60% of the youngsters had experienced one or more AOM episodes, with about 24% having three or more.

The levels reflect a decline from results of a 1989 study based in Boston indicating that by age 3 more than 80% of children had experienced at least one AOM episode and 40% had had at least three.

When the authors looked at the type of pathogens in middle-ear fluid, they found that since pneumococcal vaccines were introduced, the main source of infection had shifted from S pneumoniae to Haemophilus influenzae and Moraxella catarrhalis. The team found no evidence of a trend toward increased culture-negative results from middle-ear fluid sampling since childhood pneumococcal vaccines were introduced.

In looking for possible differences in risk factors over the study period, the group found that the factors hadn't changed. The main ones were child care attendance, family history of AOM, and experiencing AOM at a young age. Breastfeeding in the first 6 months was protective.

The researchers concluded that the epidemiology but not the risk factors have changed substantially since the introduction of pneumococcal conjugate vaccines and the use of more stringent diagnostic criteria.

Study design caveats, but a clear message on vaccine use

In a commentary in the same issue, two experts wrote that the bacterial findings are compelling and confirm those of other reports, but they said the study design limits generalizable conclusions that can be drawn about first infections. The authors are Richard Wasserman, MD, MPH, with the University of Vermont Children's Hospital, and Jeffrey Gerber, MD, PhD, with the Children's Hospital of Philadelphia.

While they praised the prospective data collection and use of rigorous AOM diagnostic criteria, Wasserman and Gerber note that the children in the study received initial treatment that strayed in three ways from the most recent AAP guidelines: routine tympanocentesis, treatment with amoxicillin/clavulanate acid (instead of just amoxicillin), and duration of treatment.

An area that remains murky is the best choice for antibiotic therapy, they wrote. Though the study authors used amoxicillin/clavulanate based on results from testing middle-ear fluid, no head-to-head studies have been done to compare the broader-spectrum antibiotic with amoxicillin, the drug the AAP recommends for most children with AOM. The commentators said trials comparing different antibiotic choices and treatment durations are greatly needed.

The main take-away from the study is that AOM incidence seems to be decreasing as use of pneumococcal vaccine expands. "Keep using [pneumococcal conjugate vaccines] and keep following the evidence-based AAP guidelines, which reflect the most comprehensive review of evidence regarding treatment," said Wasserman and Gerber.

See also:

Aug 7 Pediatrics study

Aug 7 Pediatrics commentary

Aug 7 Pediatrics press release

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