Emergence of invasive pneumococcal disease caused by nonvaccine serotypes in the era of 7-valent conjugate vaccine.
BACKGROUND
Little is known about the epidemiology of invasive pneumococcal disease (IPD) after the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) in Spain and other European countries.


METHODS
We performed a 10-year prospective study including all children with culture-proven IPD admitted to Sant Joan de Deu Hospital, a children's center in the southern area of Barcelona, Catalonia, Spain. PCV7 was introduced in June 2001, and the current estimate of PCV7 coverage is 45%-50%.


RESULTS
Comparing the prevaccine period (1997-2001) with the vaccine period (2002-2006), among children aged <2 years, the rate of IPD increased from 32.4 episodes per 100,000 population to 51.3 episodes per 100,000 population (an increase of 58%; 95% confidence interval, 2%-145%), and among children aged 2-4 years, the rate increased from 11.3 episodes per 100,000 population to 26.5 episodes per 100,000 population (an increase of 135%; 95% confidence interval, 31%-320%). At clinical presentation, the rate of pneumonia and/or empyema among children aged <5 years increased from 3.6 episodes per 100,000 population to 15.1 episodes per 100,000 population (an increase of 320%; 95% confidence interval, 98%-790%). These increased rates of IPD were caused by non-PCV7 serotypes, which represented 38% and 72% of infecting serotypes in the prevaccine and vaccine periods, respectively (P=.001). Penicillin resistance decreased from 48% in the prevaccine period to 27% in the vaccine period (P=.005). In the vaccine period, there was an emergence of previously established virulent clones of non-PCV7 serotypes 1 and 5. There was also an increase in the prevalence of serotypes 19A and 6A expressed with different clonal types, including Spain(23F)-1 and Spain(6B)-2.


CONCLUSIONS
Since the introduction of PCV7 for children, there has been an emergence of IPD caused by virulent clones of non-PCV7 serotypes that has been associated with significant clinical changes and a decrease in antibiotic resistance.
Muñoz-Almagro
Carmen
C
Department of Microbiology, Hospital Universitari Sant Joan de Deu, Esplugues, Spain.
Jordan
Iolanda
I
Gene
Amadeo
A
Latorre
Cristina
C
Garcia-Garcia
Juan J
JJ
Pallares
Roman
R
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D008297:Male; D022401:Meningococcal Vaccines / Q000276:immunology / Q000627:therapeutic use*; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000276:immunology / Q000627:therapeutic use*; D011446:Prospective Studies; D012703:Serotyping; D013030:Spain / Q000453:epidemiology; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification
D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines