Relating Pneumococcal Carriage Among Children to Disease Rates Among Adults Before and After the Introduction of Conjugate Vaccines

Abstract

The use of pneumococcal conjugate vaccines (PCVs) in children has a strong indirect effect on disease rates in adults. When children are vaccinated with PCVs, other serotypes that are not targeted by the vaccine can increase in frequency (serotype replacement) and reduce the direct and indirect benefits of the vaccine. To understand and predict the likely impacts of serotype replacement, it is important to know how patterns in the transmission of serotypes among children relate to disease rates in adults. We used data on pneumococcal carriage and disease from Navajo Nation children and adults collected before and after the routine use of PCVs (1998-2012). Using regression models within a Bayesian framework, we found that serotype-specific carriage and invasiveness (disease incidence divided by carriage prevalence) had similar patterns in children and adults. Moreover, carriage in children, invasiveness in children, and a serotype-specific random intercept (which captured additional variation associated with the serotypes) could predict the incidence serotype-specific pneumococcal disease in adults 18-39 years of age and those 40 years of age or older in the era of routine use of PCVs. These models could help us predict the effects of future pneumococcal vaccine use in children on disease rates in adults, and the modeling approach developed here could be used to test these findings in other settings.

Molecular surveillance on Streptococcus pneumoniae carriage in non-elderly adults; little evidence for pneumococcal circulation independent from the reservoir in children

“…This supports an assumption that serotypes with high frequencies in carriage in vaccinated-infants, such as serotypes 6C/D and 15A/B/C in this study, may herald an increase in frequency in adult carriage and in disease in near future 20 . However, our panel of serotyping assays was unable to identify the serotype(s) present in a large fraction of adult samples that were qPCR-positive for pneumococci, including the majority of samples from childless adults.…”

“…However, reduced circulation of VTs has allowed for the emergence of non-vaccine serotypes (NVT), with near complete replacement of VTs in carriage in vaccinated children and to a lesser extent in disease across the whole population 12 13 14 16 17 18 . The current understanding of the direct and herd effects of vaccination is based mostly on data on carriage in very young children 19 20 and data on IPD which is dominated by cases in adults 10 11 12 18 . The focus on young children in surveillances on carriage is justified by high colonisation rates of over 50% 15 21 compared to several-fold lower carriage prevalence in other age groups 22 23 24 25 .…”

Pneumococcal lineages associated with serotype replacement and antibiotic resistance in childhood invasive pneumococcal disease in the post-PCV13 era: an international whole-genome sequencing study

“…uk/ena conserved in the child population younger than 3 years. 32 Two-sided p values of less than 0•05 were considered significant. Multiple testing correction was done using the Benjamini-Hochberg false discovery rate of 5% when number of tests is greater than ten.…”

Differences in Pneumococcal Serotype Replacement in Individuals with and without Underlying Medical Conditions

“…In particular the balance of vaccine serotypes to non-vaccine serotypes during the pre-PCV period is important. Such variations in IPD serotype distribution could occur due to differential invasiveness of some serotypes in children and adults or due to variations in exposure between populations 21 . In groups in which a large fraction of IPD in the pre-PCV period was due to non-vaccine serotypes, serotype replacement offset a larger fraction of the decline in IPD.…”