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

Introduction: Mexico was the 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.