Acute Mastoiditis in the Pneumococcal Conjugate Vaccines Era Sharon Ovnat Tamir, MD ,Tal Marom, MD Department of Otolaryngology-Head and Neck Surgery, Edith Wolfson Medical Center, Tel Aviv University Sackler School of Medicine, Holon, Israel ABSTRACT INTRODUCTION RESULTS Following the introduction of the 7- and 13-valent pneumococcal conjugate vaccines, we observed an inverse relation between the increasing rate of immunized children and the proportion of middle ear fluid cultures positive for S. pneumoniae collected from acute mastoiditis episodes among a subset of children <6 years, who had initially presented with "severe" acute otitis media, and had bacterial cultures which were collected during tympanocentesis or from spontaneous otorrhea. Acute mastoiditis (AM) is a suppurative complication of acute otitis media (AOM). The most common otopathogen in AM is Streptococcus pneumoniae. In an attempt to control the impact of pneumococcal diseases, pneumococcal conjugate vaccines (PCVs) were gradually implemented in many countries during the past decade. In Israel, PCV7 has been formally introduced in the National Immunization Program in July 2009, and was replaced by PCV13 in November 2010 . Both vaccines were/are given at 2, 4 and 12 months. This change in the vaccination regime allowed us to study the dynamics of AM incidence and bacteriology in a subset of children with AOM throughout a short timeframe, from the pre-PCV7 era to the post-PCV13 era. 279 children contributed 295 "severe" AOM episodes. Of them, 57 children presented with 58 AM episodes, which represented an incidence rate of ~1 AM episode/5 "severe" AOM episodes. Table 1 displays demographic and microbial data of AM episodes according to the study years. AM developed despite antibiotic therapy in 29 (50%) episodes. The rest of AM episodes (27, 50%) presented in an abrupt, sudden course. Single bacterium grew in 19 (90%) of specimens, and multiple bacteria grew in 2 (10%) of specimens. S. pneumoniae and H. influenzae were cultured as single organisms in 16(76%), and 2(10%), respectively. S. pneumoniae proportion in AM cultures declined from 2010, and there was no growth of S. pneumoniae in 2013. In 2008, none of the children was PCV immunized, whereas ≥90% of the children 2011-2013 were PCV7/PCV13 immunized (Figure 1). "Any prior PCV13" immunized children had significantly lower proportion of S. pneumoniae positive cultures, when compared with unimmunized or "Any PCV7 immunized" children, p=0.03 and p=0.04, respectively (Figure 2). Figure 2. Otopathogens distribution, by PCV status. Mc, Moraxella catarrhalis, NTHi, Non-typeable Haemophilus influenzae, Sp, Streptococcus pneumoniae Asterisk (*) denotes significant reduction of positive S. pneumoniae positive MEF cultures in acute mastoiditis cases in PCV13 immunized children (15%), when compared with unimmunized children (41%) and PCV7 immunized children (50%), p=0.03 and p=0.04, respectively. DISCUSSION We showed that following PCV7 introduction, and more obviously following PCV13 introduction, the proportion of S. pneumoniae positive MEF cultures from AM episodes significantly decreased. Due to the short interval between the introductions of PCV7 and PCV13 in Israel (spaced only 14 months), we were not able to witness any AM time trends after PCV7 introduction, as reported elsewhere (5-9). Our main strengths are reporting MEF cultures, and not relying on nasopharyngeal cultures and knowledge of the exact PCV status for each child at his AM presentation. Limitations include the small number of patients and lack of serotype identification. METHODS AND MATERIALS Year (No. of eligible AOM episodes) 2008 (67) 2009 (48) 2010 (53) 2011 (49) 2012 (39) 2013 (39) AM episodes (% of AOM episodes) 12 (18) 7 (15) 8 (15) 12 (25) 12 (31)1 7 (18) Boys 10 (83) 4 (58) 6 (75) 4 (33) 11 (92) 2 (28) Age <2 years 6 (50) 9 (75) 5 (72) Previously treated with antibiotics, 4 (50) 5 (42) 8 (75) Patient undergoing surgical intervention 2 (17) 0 (0) 3 (42) Otherwise healthy children aged <6 years who presented to during 2008-2013 with "severe" AOM, defined as an AOM episode which either required tympanocentesis, due to lack of clinical improvement after ≥48 hours of antibiotic therapy, or presented with spontaneous otorrhea, were identified. Of them, we identified AM episodes (ICD code 383.0X). AM diagnosis was based on clinical findings (post-auricular tenderness, erythema or swelling, protruding auricle, palpable/fluctuating mass), and systemic signs (fever, lethargy, irritability, poor feeding, diarrhea). In all eligible children, middle ear fluid (MEF) cultures were collected and processed for conventional cultures. MEF cultures positive for external ear canal saprophytes were excluded. Each child was categorized according to his PCV status as "Unimmunized", if he had not received any dose of PCV, or "Any PCV7/PCV13 immunized", if he had received ≥1 dose(s) of PCV7/PCV13, respectively. CONCLUSIONS CONCLUSION We show for the first time that AM incidence and bacteriology have changed after PCV13 introduction. Further studies are warranted to monitor all-cause and pneumococcal-AM in the post-PCV13 era. Table 1. Demographic and microbial data, by study years (n=58). AOM, acute otitis media, AM, acute mastoiditis. Data are presented as n (%). . PCV13 FURTHER READING Tamir SO, et al. Acute Mastoiditis in the Pneumococcal Conjugate Vaccine Era. Clin Vaccine Immunol., Vol. 21 (8), pp.1189-91, 2014. CONTACT Tal Marom, MD Department of Otolaryngology-Head and Neck Surgery Edith Wolfson Medical Center Tel Aviv Sackler School of Medicine P.O. Box 5 58100 Holon Israel E-mail: talmarom73@gmail.com Figure 1. PCV status of the study population, by year. Any PCV immunized, children who had received ≥1 dose(s) of PCV7/PCV13. Unimmunized, children who had not been PCV immunized. .