Assessing the impact of pneumococcal conjugate vaccines on invasive pneumococcal disease using polymerase chain reaction-based surveillance: an experience from South Africa.
BMC Infect Dis
; 15: 450, 2015 Oct 26.
Article
en En
| MEDLINE
| ID: mdl-26496761
ABSTRACT
BACKGROUND:
The use of molecular diagnostic techniques for the evaluation of the impact of pneumococcal conjugate vaccines (PCVs) has not been documented. We aimed to evaluate the impact of PCVs on invasive pneumococcal disease (IPD) using polymerase chain reaction (PCR)-based techniques and compare with results obtained from culture-based methods.METHODS:
We implemented two independent surveillance programs for IPD among individuals hospitalized at one large surveillance site in Soweto, South Africa during 2009-2012 (i) PCR-based (targeting the lytA gene) syndromic pneumonia surveillance; and (ii) culture-based laboratory surveillance. Positive samples were serotyped. The molecular serotyping assay included targets for 42 serotypes including all serotypes/serogroups included in the 7-valent (PCV-7) and 13-valent (PCV-13) PCV. The Quellung reaction was used for serotyping of culture-positive cases. We calculated the change in rates of IPD (lytA- or culture-positive) among HIV-uninfected children aged <2 years from the year of PCV-7 introduction (2009) to the post-vaccine years (2011 or 2012).RESULTS:
During the study period there were 607 lytA-positive and 1,197 culture-positive cases that were serotyped. Samples with lytA cycle threshold (Ct)-values ≥35 (30.2 %; 123/407) were significantly less likely to have a serotype/serogroup detected for serotypes included in the molecular serotyping assay than those with Ct-values <35 (78.0 %; 156/200) (p < 0.001). From 2009 to 2012 rates of PCV-7 serotypes/serogroups decreased -63.8 % (95 % CI -79.3 % to -39.1 %) among lytA-positive cases and -91.7 % (95 % CI -98.8 % to -73.6 %) among culture-positive cases. Rates of lytA-positive non-vaccine serotypes/serogroups also significantly decreased (-71.7 %; 95 % CI -81.1 % to -58.5 %) over the same period. Such decline was not observed among the culture-positive non-vaccine serotypes (1.2 %; 95 % CI -96.7 % to 58.4 %).CONCLUSIONS:
Significant downward trends in IPD PCV-7 serotype-associated rates were observed among patients tested by PCR or culture methods; however trends of non-vaccine serotypes/serogroups differed between the two groups. Misclassifications of serotypes/serogroups, affecting the use of non-vaccine serotypes as a control group, may have occurred due to the low performance of the serotyping assay among lytA-positive cases with high Ct-values. Until PCR methods improve further, culture methods should continue to be used to monitor the effects of PCV vaccination programs on IPD incidence.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Infecciones Neumocócicas
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Streptococcus pneumoniae
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Reacción en Cadena de la Polimerasa
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Vacunas Conjugadas
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Vacunas Neumococicas
Tipo de estudio:
Screening_studies
Límite:
Adolescent
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Adult
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Aged
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Child
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Child, preschool
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Female
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Humans
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Infant
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Male
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Middle aged
País/Región como asunto:
Africa
Idioma:
En
Revista:
BMC Infect Dis
Asunto de la revista:
DOENCAS TRANSMISSIVEIS
Año:
2015
Tipo del documento:
Article
País de afiliación:
Estados Unidos