Childhood invasive pneumococcal disease and acute otitis media in Central Greece during 2005-2024 - A report at the doorstep of the new multivalent PCV era

Abstract

Background: In Greece, pneumococcal conjugate vaccines (PCVs) became sequentially available: 7-valent in October 2004, 10-valent in May 2009, 13-valent in June 2010 and 15-valent in March 2023; soon after availability all vaccines were incorporated in the National Ιmmunization Program except for PCV7 which was implemented in January 2006. Since July 2010, PCV13 has been the most commonly used PCV. Surveillance at a regional and a national level is a valuable tool to monitor the impact of PCVs.

Methods: At the University General Hospital of Larissa (single academic tertiary care referral center for Central Greece) we prospectively obtained samples from 0 to 15-year-old children consequently diagnosed with invasive pneumococcal disease (IPD) or acute otitis media (AOM) with spontaneous perforation of the tympanic membrane (SPTM) during three time periods: the PCV7 (2005-2010), the early-mid PCV13 (2011-2016) and the late PCV13 (2017-2024) periods. Pneumococci were serotyped by capsular swelling. PCR was applied on pleural fluid and CSF specimens.

Results: A total of 106 (61 IPD and 45 AOM with SPTM) serotype-evaluable samples were obtained. Serotypes 19A and 19F peaked in 2005-2010 and decreased thereafter. Increased number of IPD cases due to serotype 3 were noted in the 2011-2016 and 2017-2024 periods. The emergence of non-PCV13 serotypes in IPD and AOM with SPTM was noted in the late PCV13 period. In 2017-2024 the most common serotypes responsible for IPD were 3 and 12F. The projected additional protection from IPD, beyond that of PCV13, offered by PCV15 and PCV20 during 2017-2024 was 10 % and 30 %, respectively. The respective additional protection from AOM offered by the two vaccines was 0 % and 21.4 %.

Conclusion: Our findings in Central Greece suggest that PCVs of increasing valency are expected to provide substantial additional coverage for pneumococcal disease as compared to PCV13.

Keywords: 13-valent pneumococcal conjugate vaccine; 15-valent pneumococcal conjugate vaccine; 20-valent pneumococcal conjugate vaccine; Acute otitis media; Children; Invasive pneumococcal disease.