Pneumococcal disease: emergence of serotypes 19A and 7F following conjugate pneumococcal vaccination in a Mexican hospital

Abstract

Introduction: Mexico  was  the  first  country  to  initiate  massive  vaccination  with   heptavalent  pneumococcal  conjugate  vaccine  (PCV-7)  in  children.  There  is  no  information  regarding  pneumococcal  invasive  disease  (PID)  in  children  before  and  after  implementation  of  PCV-7  in  Mexico  or elsewhere  in  Latin America. Methodology: During  October  2005 to September  2010, active  surveillance  for  pediatric  PID  was  initiated  at  Tijuana  General  Hospital. Only culture-confirmed cases from sterile  fluids  were  included in the study.  Serotype identification was also performed.  Results: Twenty-eight pediatric PID cases were confirmed. Streptococcus pneumoniae was the main  cause  of  pleural  empyema  (n = 13). It was also the  second most common cause  of  confirmed  bacterial  meningitis  (n = 10),  followed  by  Neisseria  meningitidis (n = ?),  and  the  only  cause  of  otomastoiditis  with  bacterial  isolation  (n = 5).  Vaccine-associated  serotypes  decreased  from  54%  before  PCV-7  introduction  to  the  vaccination  schedule,  to  only  5.6%  after  PCV-7  implementation. Serotypes  19A  and  7F  (47%  and  33%  respectively)  were  predominant  following  PCV-7  vaccination. Conclusions: Serotype  substitution  in  PID  is  present  in the  northern  border  of  Mexico  following  PCV-7  vaccination  in  children.