Using Pneumococcal Carriage Data to Monitor Postvaccination Changes in Invasive Disease

Abstract

Pneumococcal conjugate vaccines (PCVs) have been introduced worldwide. However, few developing countries have high-quality surveillance systems available for monitoring vaccine impact. We evaluated whether data from nasopharyngeal carriage studies can be used to accurately monitor post-PCV changes in the incidence of invasive pneumococcal disease (IPD) among children under 5 years of age. For various dates during 1991-2010, data on nasopharyngeal pneumococcal carriage and on IPD before and after administration of 7-valent PCV (PCV7) were available from England and Wales, the Netherlands, the Navajo and White Mountain Apache American Indian populations, and the US states of Massachusetts and Alaska. We estimated the change in carriage prevalence for each serotype in each study and then either calculated the average change (inverse variance-weighted) among vaccine and nonvaccine serotypes (model 1) or used mixed-effects models to estimate the change for each serotype individually, pooling serotype data within or between studies (models 2 and 3). We then multiplied these values by the proportion of IPD caused by each serotype during the pre-PCV7 period to obtain an estimate of post-PCV7 disease incidence. Model 1 accurately captured overall changes in IPD incidence following PCV7 introduction for most studies, while the more detailed models, models 2 and 3, were less accurate. Carriage data can be used in this simple model to estimate post-PCV changes in IPD incidence.

Pharyngeal Colonization by Streptococcus pneumoniae in Older Children and Adolescents in a Geographical Area Characterized by Relatively Limited Pneumococcal Vaccination Coverage

“…Our findings conflict with those of most of the studies of carriage in children after the implementation of PCV7 vaccination programmers, which indicate lower carriage rates in vaccinated than in unvaccinated subjects. [1][2][3][4] However, most of these studies were carried out a few months after infant vaccination and in areas in which PCV7 coverage was very high, and the findings probably reflect the immediate direct and indirect effects of PCV7 in subjects who are at relatively low risk of pneumococcal transmission and colonization because of herd immunity secondary to almost universal vaccination. [1][2][3][4] We enrolled school-age children and adolescents who had received the last dose of PCV7 on an average of 6 year before and who were in continuous contact with a large number of unvaccinated contemporaries for all the life.…”

“…[1][2][3][4] However, most of these studies were carried out a few months after infant vaccination and in areas in which PCV7 coverage was very high, and the findings probably reflect the immediate direct and indirect effects of PCV7 in subjects who are at relatively low risk of pneumococcal transmission and colonization because of herd immunity secondary to almost universal vaccination. [1][2][3][4] We enrolled school-age children and adolescents who had received the last dose of PCV7 on an average of 6 year before and who were in continuous contact with a large number of unvaccinated contemporaries for all the life. Both of these factors could have conditioned colonization rates in vaccinated children because the protection against colonization offered by PCV7 might have waned over time and the setting of high transmission rates might have favored new colonization's of the same serotypes as those included in the vaccine.…”

“…2,3 Consequently, measuring carriage can provide serotypespecific data about direct and indirect PCV-induced protection in individual subjects. 4 However, estimating the efficacy of PCVs against S. pneumoniae colonization has not been standardized, which can make it difficult to distinguish differences in efficacy from differences in study methods. Carrier status after PCV administration may significantly vary depending on the PCV, time since vaccine administration, infection pressure, carriage prevalence in the general population and the immune system characteristics of vaccinated subjects.…”

The Efficacy and Duration of Protection of Pneumococcal Conjugate Vaccines Against Nasopharyngeal Carriage

“…2 Recently, emphasis has been put on the importance of carriage as a proxy measure for PCV impact assessments and for using carriage as an additional and essential biomarker in the licensure pathway of new pneumococcal vaccines. 3,4 A recent systematic review of the direct impact of PCVs by dosing schedules 5 showed consistent reductions in carriage of the serotypes targeted by the vaccine, including a few years after vaccination, with evidence favoring 3-dose schedules over fewer doses. However, systematic estimates of the efficacy of PCVs against carriage and the duration of protection conferred are lacking.…”

Preventing non bacteremic pneumococcal pneumonia in older adults

“…2,24,[28][29][30][31] In populations where children have received PCV7, monitoring changes in NP carriage in those <5 y of age has been shown to accurately predict changes in childhood IPD. 32 Moreover, a strong correlation has been established between reductions in NP carriage and IPD in older adults at the individual as well as population level.…”