We have published several studies related to Invasive Pneumococcal Disease, and effectiveness of Pneumococcal Conjugate Vaccines: 7-valent (PCV7) and 13-valent (PCV13). This is the first Latin American, prospective study looking for Otomastoiditis (OM) in children, and the impact of PCV13 on this disease. Methods: Since October/1st/2005 until September/30th/2017, prospective surveillance to identify all children<16 years old with OM at the Tijuana, Mexico, General Hospital was performed. OM was diagnosed with otoscopy, and tomographic signs of OM. Bacterial identification was obtained either from mastoids and/or supramastoid abscesses, and bacterial identification by conventional cultures. Pneumococcal serotyping was performed by the Quellung Reaction (Statens Serum Institute®). Results: Twenty cases of OM were identified. Median age at admission was 32 months (6 months–15 years). Median hospitalization days of 10 (5–115). Mastoidectomy was performed in all. Bacterial isolation was successful in 18 (85.7%). S. pneumoniae was isolated in 14 (77.77%). For Pneumococcal OM: before PCV7 introduction (19 months of surveillance) there were 0.158 cases per month (6A, 18C, 7F, one of each), post-PCV7 universal vaccination (61 months of surveillance) decreased to 0.114 cases per month (serotypes 19A(3), 3(2), 7F(1), 12F(1), PCV7 impact of 27.8%), and following PCV13 implementation (76 months of surveillance) dropped to 0.052 cases per month (serotypes 3(1), 33F(1), 35B(1), 24F(1), PCV13 impact of 67%), with no cases of S. pneumoniae serotype 19A following PCV13. Conclusion: Although relatively uncommon, OM was associated with important morbidity (mastoidectomy) and long hospitalization. S. pneumoniae was the leading cause, with high impact of PCV13 (67%), and a possible disappearance of serotype 19A.

Both the 7 and 13-valent Pneumococcal conjugate vaccines (PCV-7, and PCV-13, respectively) have mostly been implemented, and proved to be highly effective in several countries to decrease Invasive Pneumococcal Disease (IPD) in children (and adults by herd effect), such as septicemia, meningitis, pleural empyema, among others [1-10]. Even though these vaccines initially were not implemented to reduce Acute Otitis Media (AOM), various studies have shown its effects on decreasing this “mucosal” disease, as a result of reducing both nasopharyngeal carriages, and the first AOM episode when administered promptly in infancy [11-14]. However, its effectiveness on decreasing Otomastoiditis (OM), a local/suppurative complication of AOM, has not been widely published.

The Italian, 15 years retrospective study done by Balsamo, et al. [15], did not show a statistical difference of OM before and an after any PCV used. However, in this publication, from all 143 patients enrolled, isolation was not reported, and many patients did not undergo mastoidectomy. However, in the study published by Marom, et al. [16], which retrospectively analyzed all causes by both uncomplicated and complicated AOM in the USA between 2001-2011, attack rates of cases of OM dropped from 0.6/100,000 to 0.32/100,000 (p=0.05) since 2009 (during implementation of PCV13), with no effect with PCV7 vaccination. Similar findings are published by Tamir, et al., from which based on their findings, PCV13 had more effect than PCV7 on Pneumococcal OM in Israel.

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