Association Between the Decline in Pneumococcal Disease in Unimmunized Adults and Vaccine-Derived Protection Against Colonization in Toddlers and Preschool-Aged Children.

Daniel M Weinberger,Noga Givon-Lavi,Ron Dagan,Gili Regev-Yochay,Virginia E Pitzer

doi:10.1093/aje/kwy219

Abstract

Vaccinating children with pneumococcal conjugate vaccine (PCV) disrupts transmission, reducing disease rates in unvaccinated adults. When considering changes in vaccine dosing strategies (e.g., removing doses), it is critical to understand which groups of children contribute most to transmission to adults. We used data from Israel (2009–2016) to evaluate how the buildup of vaccine-associated immunity in children was associated with declines in invasive pneumococcal disease (IPD) due to vaccine-targeted serotypes in unimmunized adults. Data on vaccine uptake and prevalence of colonization with PCV-targeted serotypes were obtained from children visiting an emergency department in southern Israel and from surveys of colonization from central Israel. Data on IPD in adults were obtained from a nationwide surveillance study carried out in Israel. We compared the trajectory of decline of IPD due to PCV-targeted serotypes in adults with the decline of colonization prevalence and increase in vaccine-derived protection against pneumococcal carriage among different age groupings of children. The declines in IPD in adults were most closely associated with the declines in colonization and increased vaccination coverage among children in the age range of 36–59 months. This suggests that preschool-aged children, rather than infants, are responsible for maintaining the indirect benefits of PCVs.

Highlights

While pneumococcal conjugate vaccine (PCV) programs have effectively reduced the burden of disease in many countries, the cost of the vaccine remains a major concern in both affluent and resource-poor settings
As a further evaluation of changes in prevalence among healthy children, we evaluated changes in the prevalence of pneumococcal conjugate vaccine 7 (PCV7)-targeted serotypes among healthy children living in central Israel who were sampled as part of a series of cross-sectional surveys of nasopharyngeal colonization [20, 21]
We focused on PCV7 serotypes only because there was a brief period of time between the introduction of PCV7 and the introduction of 13-valent pneumococcal conjugate vaccine (PCV13), which made it difficult to disentangle early serotype replacement from vaccine-associated effects

Summary

Introduction

While PCV programs have effectively reduced the burden of disease in many countries, the cost of the vaccine remains a major concern in both affluent and resource-poor settings. Because of the importance of indirect protection that results from the use of PCVs, it would be desirable for any new dosing strategy to be able to maintain indirect protection [7] To consider this issue, it is critical to determine which groups of young children contribute most to the indirect benefit of the vaccine for unimmunized adults. The decline in IPD due to vaccine-targeted serotypes in adults is delayed and slower than the decline observed in vaccinated children [16] This might indicate that the transmission benefit (i.e., indirect effect) of vaccinating children during the first year of life is not realized until a few years later when those children reach an older age group. We used a unique and ongoing survey of children in Israel that allowed us to quantify vaccine uptake and IPD rates over time

Methods

Results

Conclusion