By Ingrid Grasmo
Researchers have identified a pneumococcal conjugate vaccine (PCV) that is effective for treating bacteremic pneumococcal community-acquired pneumonia (CAP) in children aged 5 years or younger.
The findings are a result of the identification of serotypes 14 and 19A as the most frequent causes of CAP in Italy, where only 50% of children are vaccinated.
"The circulation and antibiotic resistance of these serotypes needs to be carefully and continuously monitored," say Nicola Principi (Universita degli Studi di Milano, Italy) and colleagues.
For the study, the researchers determined pneumococcal serotypes from 510 children aged 5 years or younger with radiographically confirmed CAP admitted to hospital in five different regions of Italy during 2008-2011. Diagnosis for CAP was confirmed by polymerase chain reaction (PCR) positive for Streptococcus pneumoniae.
Complicated pneumonia was twice as likely to occur among pneumococcal cases (odds ratio [OR]=1.96) compared with non-pneumococcal cases, with empyema the main complication. In total, 47.2% of children were fully vaccinated with PCV7 and the remaining were not vaccinated or incompletely vaccinated.
Results from real-time PCR serotyping performed for 66 children revealed that the most frequent serotype was 19A (25.8%) followed by serotype 14 (15.1%), serotype 4 (7.6%), and serotype 3 (6.1%).
Among complicated cases, 33.3% were due to serotype 19A, but the prevalence of this serotype in complicated cases was not significantly different from that of other serotypes.
Analysis of distribution of serotypes by vaccination status showed that pneumococcal CAP occurred in 62.1% of children who were incompletely vaccinated with PCV7 and 35.9% of fully vaccinated children.
The protection offered by PCV7 against bacteremic CAP in fully vaccinated children during the study period was 76%, with an overall theoretical coverage against pneumococcal bacteremic CAP of 31.8%, 37.9%, and 71.2% for PCV7, PCV10, and PCV13.
Writing in the Pediatric Infectious Disease Journal, Principi and team conclude: "On the basis of these epidemiological data and the composition of the new vaccines, it can be concluded that PCV13 seems the best solution at the moment available to overcome the limitations of PCV7, whereas the theoretical protection offered by PCV10 against bacteremic CAP is only slightly higher than that of PCV7."
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