Pneumococcal Carriage in Young Children One Year after Introduction of the 13-Valent Conjugate Vaccine in Italy

Abstract

BackgroundIn mid 2010, the 7-valent pneumococcal conjugate vaccine (PCV7) was replaced by the 13-valent conjugate vaccine (PCV13) for childhood immunization in Italy. Our objective in this study was to obtain a snapshot of pneumococcal carriage frequency, colonizing serotypes, and antibiotic resistance in healthy children in two Italian cities one year after PCV13 was introduced.MethodsNasopharyngeal swabs were obtained from 571 children aged 0-5 years from November 2011-April 2012. Pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. Penicillin and/or erythromycin non-susceptible isolates were analyzed by Multi Locus Sequence Typing (MLST).ResultsAmong the children examined, 81.2% had received at least one dose of PCV7 or PCV13 and 74.9% had completed the recommended vaccination schedule for their age. Among the latter, 57.3% of children had received PCV7, 27.1% PCV13, and 15.6% a combination of the two vaccines. The overall carriage rate was 32.9%, with children aged 6-35 months the most prone to pneumococcal colonization (6-23 months OR: 3.75; 95% CI: 2.19-6.43 and 24-35 months OR: 3.15, 95%CI: 2.36-4.22). A total of 184 pneumococcal isolates were serotyped and divided into PCV7 (5.4%), PCV13 (18.0%), and non-PCV13 (82.0%) serotypes. Serotypes 6C, 24F, and 19A were the most prevalent (10.3%, 8.6%, and 8.1%, respectively). The proportion of penicillin non-susceptible (MIC >0.6 mg/L) isolates was 30.9%, while 42.3% were erythromycin resistant. Non-PCV13 serotypes accounted for 75.4% and 70.8% of the penicillin and erythromycin non-susceptible isolates, respectively.ConclusionsOur results revealed low rates of PCV7 and PCV13 serotypes in Italian children, potentially due to the effects of vaccination. As the use of PCV13 continues, its potential impact on vaccine serotypes such as 19A and cross-reactive serotypes such as 6C will be assessed, with this study providing a baseline for further analysis of surveillance isolates.

Pneumococcal carriage in young children after introduction of PCV13 in Hong Kong

“…Non-PCV13 serotype 6C and serogroup 15 were the most frequently isolated in our study. Similar results have been reported from overseas and local studies [12][13][14][15][16][17]23]. Serotype 6C has been reported to be disease causing with an increase in prevalence of IPD caused by 6C in the post PCV era [32][33][34][35].…”

“…Serotype replacement in pneumococcal carriage in these children was evident with the emergence of serogroup 15 and serotype 6C. Local prevalence of pneumococcal carriage as shown by our study was low when compared with data from other countries which show carriage rates of 28.8-35% in children under 2 years old [12,14,15,[23][24][25]. Previous local surveillance studies have also shown lower pneumococcal carriage rates than Caucasian and other Asian populations [12,14-17,23-26], which may explain the lower IPD burden in Hong Kong than other countries [27].…”

“…Previous local surveillance studies have also shown lower pneumococcal carriage rates than Caucasian and other Asian populations [12,14-17,23-26], which may explain the lower IPD burden in Hong Kong than other countries [27]. All subjects in our cohort were vaccinated appropriately for age with PCV13 while in some other cohorts, the reported PCV uptake rates were lower (13.7-39.9%) [12,23]. While some studies found a reduction in overall nasopharyngeal pneumococcal colonization after introduction of PCV [17,24,28], others did not report similar findings [14,25].…”

“…Although the effect of PCV on the overall carriage rate remains uncertain, the high vaccine coverage with PCV13 may be one of the factors accounting for the low carriage rate found in our population. Other characteristics in our cohort that may explain the low carriage rate include: (i) fewer subjects in our cohort (32%) had siblings younger than 6 years compared with other cohorts (47-51%) [12,14]; (ii) the rate of group care attendance was lower in our cohort (12.8%) compared with other studies (37-79%) [12,14,23]; (iii) our cohort had a relatively higher rate of recent antibiotic use [12,14]. Pneumococcal carriage is consistently associated with the presence of siblings under 6 years old and group care attendance [12,14,23,30].…”

Carriage of Haemophilus influenzae is associated with pneumococcal vaccination in Italian children

“…In 2012 we performed a pneumococcal carriage study in children in two Italian cities at the introduction of PCV13, which revealed a high prevalence on NVT [13]. A portion of the children from this study was also examined for H. influenzae colonization.…”