ID Consult

Why is AOM frequency decreasing in the pneumococcal conjugate vaccine era?


 

In 2000, pneumococcal conjugate vaccine 7 (PCV7) was introduced in the United States, and in 2010, PCV13 was introduced. When each of those vaccines were used, they reduced acute otitis media (AOM) incidence caused by the pneumococcal types included in the vaccines. In the time frame of those vaccine introductions, about one-third of AOM cases occurred because of pneumococci and half of those cases occurred because of strains expressing the serotypes in the two formulations of the vaccines. Efficacy is about 70% for AOM prevention for PCVs. The math matches clinical trial results that have shown about an 11%-12% reduction of all AOM attributable to PCVs. However, our group continues to do tympanocentesis to track the etiology of AOM, and we have reported that elimination of strains of pneumococci expressing capsular types included in the PCVs has been followed by emergence of replacement strains of pneumococci that express non-PCV capsules. We also have shown that Haemophilus influenzae has increased proportionally as a cause of AOM and is the most frequent cause of recurrent AOM. So what else is going on?

Toddler is held by mother while being vaccinated by doctor. KatarzynaBialasiewicz/Thinkstock

My colleague, Stephen I. Pelton, MD, – another ID Consult columnist – is a coauthor of a paper along with Ron Dagan, MD; Lauren Bakaletz, PhD; and Robert Cohen, MD, (all major figures in pneumococcal disease or AOM) that was published in Lancet Infectious Diseases (Dagan R et al. Lancet Infect Dis. 2016 Apr;16[4]:480-92.). They gathered evidence suggesting that prevention of early AOM episodes caused by pneumococci expressing PCV serotypes resulted in a reduction of subsequent complex cases caused by nonvaccine serotypes and other otopathogens. Thus, PCVs may have an impact on AOM indirectly attributable to vaccination.

However, the American Academy of Pediatrics made several recommendations in the 2004 and 2013 guidelines for diagnosis and management of AOM that had a remarkable impact in reducing the frequency that this infection is diagnosed and treated as well. The recommendations included:

  • Stricter diagnostic criteria in 2004 that became more strict in 2013 requiring bulging of the eardrum.
  • Introduction of “watchful waiting” as an option in management that possibly led to no antibiotic treatment.
  • Introduction of delayed prescription of antibiotic when diagnosis was uncertain that possibly led to no antibiotic treatment.
  • Endorsement of specific antibiotics with the greatest anticipated efficacy taking into consideration spectrum of activity, safety, and costs.

In the same general time frame, a second development occurred: The Centers for Disease Control and Prevention launched a national campaign to reduce unnecessary and inappropriate antibiotic use in an effort to reduce rising antibiotic resistance among bacteria. The public media and professional communication campaign emphasized that antibiotic treatment carried with it risks that should be considered by patients and clinicians.

Because of the AAP and CDC recommendations, clinicians diagnosed AOM less frequently, and they treated it less frequently. Parents of children took note of the fact that their children with viral upper respiratory infections suspected to have AOM were diagnosed with AOM less often; even when a diagnosis was made, an antibiotic was prescribed less often. Therefore, parents brought their children to clinicians less often when their child had a viral upper respiratory infections or when they suspected AOM.

Dr. Michael E. Pichichero, a specialist in pediatric infectious diseases, and director of the Research Institute at Rochester (N.Y.) General Hospital

Dr. Michael E. Pichichero

In addition, guidelines endorsed specific antibiotics that had better efficacy in treatment of AOM. Therefore, when clinicians did treat the infection with antibiotics, they used more effective drugs resulting in fewer treatment failures. This gives the impression of less-frequent AOM as well.

Both universal PCV use and universal influenza vaccine use have been endorsed in recent years, and uptake of that recommendation has increased over time. Clinical trials have shown that influenza is a common virus associated with secondary bacterial AOM.

Lastly, returning to antibiotic use, we now increasingly appreciate the adverse effect on the natural microbiome of the nasopharynx and gut when antibiotics are given. Natural resistance provided by commensals is disrupted when antibiotics are given. This may allow otopathogens to colonize the nasopharynx more readily, an effect that may last for months after a single antibiotic course. We also appreciate more that the microbiome modulates our immune system favorably, so antibiotics that disrupt the microbiome may have an adverse effect on innate or adaptive immunity as well. These adverse consequences of antibiotic use on microbiome and immunity are reduced when less antibiotics are given to children, as has been occurring over the past 2 decades.

Dr. Pichichero is a specialist in pediatric infectious diseases and director of the Research Institute at Rochester (N.Y.) General Hospital. He said he had no relevent financial disclosures. Email him at [email protected].

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