Post-PCV7 Changes in Colonizing Pneumococcal Serotypes in 16 Massachusetts Communities, 2001 and 2004

Abstract

ABSTRACT. Objective. The introduction of heptavalent conjugate pneumococcal vaccine (PCV7) has raised concerns for replacement with nonvaccine serotypes in both invasive disease and asymptomatic carriage. Analysis of colonizing serotypes among healthy children in the community provides critical data on such changes.Methods. Nasopharyngeal specimens were obtained from children who were younger than 7 years during well-child or sick visits in primary care practices in 16 Massachusetts communities during 2001 and 2004. Susceptibility testing and serotyping were performed on isolated Streptococcus pneumoniae strains. Vaccination history with PCV7 was abstracted from the medical record.Results. Among colonizing pneumococcal isolates, PCV7 serotypes decreased from 36% to 14%, and non-PCV7 serotypes increased from 34% to 55%. Overall carriage did not change (26% to 23%); neither did carriage of potentially cross-reactive serotypes (30% to 31%). The most common non-PCV7 serotypes were serotypes 11, 15, and 29. There was a substantial increase in penicillin nonsusceptibility from 8% to 25% in non-PCV7 serotypes; 35% were highly resistant to penicillin. Penicillin nonsusceptibility increased from 45% to 56% among PCV7 serotypes while remaining stable among PCV7 potentially cross-reactive strains (51% vs 54%).Conclusions. Pneumococcal colonization has changed after the introduction of PCV7, both in serotype distribution and in patterns of antibiotic resistance. The frequency of nonvaccine strains has increased, and the proportion of nonvaccine isolates that are not susceptible to penicillin has tripled. This shift toward increased carriage of nonvaccine serotypes warrants vigilance for changes in the epidemiology of invasive pneumococcal disease. B efore the release of a conjugate vaccine for US children, Streptococcus pneumoniae caused invasive disease in 1 in 500 to 600 children who were younger than 2 years. 1 In addition, rising antibiotic resistance among pneumococcal strains was a major concern among public health officials. 2,3 By 1999, 38% of laboratory isolates in children who were younger than 2 years were nonsusceptible to penicillin, 4 with higher rates reported in local areas. [5][6][7] In February 2000, heptavalent pneumococcal conjugate vaccine (PCV7) was released to provide immunity to the 7 serotypes responsible for 85% of pediatric invasive pneumococcal disease 8 and 78% of penicillin-nonsusceptible S pneumoniae (PNSP) isolates in children. 9 Prelicensure trials showed a 90% reduction in invasive disease 10 and a 23% reduction in all-cause pneumonia in the first 2 years of life. 11 Postlicensure studies have also shown declines in invasive pneumococcal disease from 188 per 100 000 to 59 cases per 100 000 in US children who are younger than 2 years. 4,12 Despite the success of PCV7 in reducing invasive disease, critical questions remain about the changing pneumococcal reservoir. Some trials of immunization with PCV7 have shown a 50% to 65% decrease in carriage of vaccine serotypes [13][14][15] and have rai...

Streptococcus pneumoniae: evolución de los serotipos y los patrones de susceptibilidad antimicrobiana en aislamientos invasores en 11 años de vigilancia en colombia (1994 -2004).

“…La vacuna heptavalente ha demostrado ser efectiva para reducir los niveles de resistencia a los antibióticos (50,53,54); un efecto similar se podría esperar en nuestro país debido a que los serotipos contenidos en la vacuna representan el 97,3% de los aislamientos con SDP. Sin embargo, como consecuencia de la vacunación se ha observado en los niños inmunizados una disminución en los serotipos vacunales con un incremento en la colonización por serotipos no contenidos en la vacuna, probablemente debido a un reemplazo de serotipos o al desenmascaramiento de poblaciones minoritarias de S. pneumoniae (50,54).…”

“…Sin embargo, como consecuencia de la vacunación se ha observado en los niños inmunizados una disminución en los serotipos vacunales con un incremento en la colonización por serotipos no contenidos en la vacuna, probablemente debido a un reemplazo de serotipos o al desenmascaramiento de poblaciones minoritarias de S. pneumoniae (50,54). El significado clínico y las consecuencias de este incremento aún no son claras y, por lo tanto, es necesario evaluar el impacto de la vacuna en la distribución de los serotipos colonizantes de S. pneumoniae en la población infantil, debido a que el uso generalizado de la vacuna conjugada podría alterar su distribución y eventualmente la enfermedad invasora.…”

Biochemical, Genetic, and Serological Characterization of Two Capsule Subtypes among Streptococcus pneumoniae Serotype 20 Strains

“…Vaccination efforts have been successful in reducing the incidence of pneumococcal disease in children and adults (3)(4)(5). However, because only a limited number of serotypes are included in the vaccines, nonvaccine serotypes can fill the ecological niche left by the overall reduction of vaccine-targeted serotypes.…”

Impact of a 16-Community Trial to Promote Judicious Antibiotic Use in Massachusetts

“…Antibiotic resistance is a community-level public health concern, and randomization of individual patients or providers would be susceptible to unacceptable contamination between intervention and control states; therefore, we conducted a 16-community, cluster-randomized trial of the Reducing Antibiotics for Children in Massachusetts (REACH Mass) intervention. We previously reported measures of parental knowledge, 27 physician self-reported behavior, 28 and antibiotic resistance rates among colonizing isolates of S pneumoniae 29,30 ; however, our primary goal was to test whether a 3-year sustained intervention decreased the number of dispensings of antibiotics to children overall. A secondary analysis tested whether the intervention increased the fraction of appropriate, narrow-spectrum agents used, compared with patterns seen in control communities.…”