Incidence rate ratios of children hospitalized with acute otitis media (hAOM) or more advanced stages, such as mastoidismus and acute mastoiditis (M+AM) declined by 10% and 20%, respectively, after introduction of pneumococcal conjugate vaccines (PCV) in the central region of Denmark, reported Bjarke B. Laursen of Aarhus University in Denmark, and associates.
The use of antibiotics for AOM prior to hospitalization increased markedly during the study period, and that may have impacted the modest reduction in hAOM and M+AM, the researchers said.
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Incidence of Streptococcus pneumoniae cases decreased from 38% in the prevaccine era to 31% in the PCV-7 era and decreased even more to 16% in the PCV-13 era. The incidence of the second most frequently isolated bacteria, group A streptococcus (GAS), fell from 17% in the prevaccine era to 16% in the PCV-13 era, becoming equal to S. pneumoniae. The “no growth” results rose from 12% in the prevaccine era to 38% and 44% in the PCV-7 and PCV-13 eras, respectively (Int J Pediatr Otorhinolaryngol. 2017 Jul 4. doi: 10.1016/j.ijporl.2017.07.002) .
In the M+AM group, S. pneumoniae–positive cases fell to 10% in the PCV-13 era, compared with 44% in the prevaccine era and 41% in the PCV-7 era. A rise in GAS-positive cultures was seen in the M+AM group, from 15% in the prevaccine era to 30% in the PCV-13 era. The “no growth” group rose in incidence from 13% of cases in the prevaccine era to 26% in the PCV-7 era and 33% in the PCV-13 era.
“This microbiological shift is worrisome, because GAS may cause very serious infections due to its invasive nature,” Dr. Laursen and associates wrote. “An increase in GAS as described in this study has not been demonstrated elsewhere so far. In contrast to our findings, the most common species to ‘take over’ in the United States was Haemophilus influenzae.
“As [S. pneumoniae] and GAS are potentially invasive pathogens causing more severe clinical signs and symptoms, such cases are more likely to be admitted compared to cases caused by non-typable Haemophilus influenzae that gives rise to more subtle middle ear infections and clinical pictures,” the researchers noted.
Considering how many patients received antibiotics prior to admission in the hAOM group, there was a slight increase from 45% in the prevaccine era to 54% in the PCV-13 era, but a “more pronounced increase was found in the M+AM group, from 27% in the prevaccine era to 46% in the PCV-13 era,” they said.
The investigators called for continued surveillance of the microbiology associated with complex AOM.
No study funding or investigator disclosure information was provided.