Potential Serotype Coverage of Three Pneumococcal Conjugate Vaccines Against Invasive Pneumococcal Infection in Italian Children

Background And Aim Of The Work: Since the introduction of the 7-valent vaccine, invasive pneumococcal disease have greatly decreased; however, changes in the distribution of pneumococcal serotypes have recently highlighted the need for vaccines with wider coverage. The aim of the work was to assess the potential serotype coverage of three pneumococcal conjugate vaccines (7-, 10- and 13-valent) against bacteremic pneumococcal pneumonia and meningitis/sepsis in Italian children.

Patients And Methods: We determined pneumococcal serotypes in immunocompetent patients who had been admitted to hospital with suspicion of invasive bacterial disease and had confirmed bacteremic pneumococcal pneumonia or meningitis/sepsis determined by molecular detection of Streptococcus pneumoniae in a normally sterile site. Positive samples were serotyped using Realtime-PCR.

Results: Between April 2008 and March 2011, a total of 144 patients (age median 4.1 years; Interquartile range 1.8-5.6) with pneumococcal meningitis/sepsis (n=43) or pneumonia (n=101) from 83 participating centers located in 19 of 20 Italian regions were serotyped. The 10 most prevalent serotypes were 1 (29.9%), 3 (16.0%), 19A (13.2%), 7F (8.3%), 5 (4.2%), 14 (4.2%), 6A (3.5%), 6B (3.5%), 18C (3.5%), 19F (3.5%). Overall, serotype coverage for PCV-7, -10 and -13 were respectively 19.4%, 61.8% and 94.4% with no statistical difference between pneumonia and meningitis/sepsis. Potential coverage was similar for children 0-2 or 2-5 years of age. Cultures resulted positive in 35/99 (35.4%) samples simultaneously obtained for both culture and RT-PCR.

Conclusion: These findings indicate that increasing the potential serotype coverage by introducing PCV13 in the vaccination schedule for infancy could provide substantial added benefit for protection from pneumococcal pneumonia or meningitis/sepsis in Italy in children below 2 years as well in older children. The importance of molecular methods for diagnosis and serotyping of invasive pneumococcal disease was confirmed.