Surveillance of pneumococcal colonization and invasive pneumococcal disease reveals shift in prevalent carriage serotypes in Massachusetts' children to relatively low invasiveness

I Yildirim; B A Little; J Finkelstein; G Lee; W P Hanage; K Shea; S I Pelton; T; he Massachusetts Dept. of Public Health

doi:10.1016/j.vaccine.2017.05.077

Surveillance of pneumococcal colonization and invasive pneumococcal disease reveals shift in prevalent carriage serotypes in Massachusetts' children to relatively low invasiveness

Vaccine. 2017 Jul 13;35(32):4002-4009. doi: 10.1016/j.vaccine.2017.05.077. Epub 2017 Jun 20.

Authors

I Yildirim¹, B A Little², J Finkelstein³, G Lee⁴, W P Hanage⁵, K Shea⁶, S I Pelton⁷; T; he Massachusetts Dept. of Public Health

Affiliations

¹ School of Medicine, Emory University, Atlanta, GA, USA; Department of Epidemiology, Rollins School of Public Health, Atlanta, GA, USA. Electronic address: inci.yildirim@emory.edu.
² Maxwell Finland Laboratories, Boston Medical Center, Boston, MA, USA.
³ Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA; Division of General Pediatrics, Boston Children's Hospital, Boston, MA, USA.
⁴ Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA, USA; Division of Infectious Diseases, Boston Children's Hospital, Boston, MA, USA.
⁵ Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
⁶ Department of Epidemiology, School of Public Health, Boston University, Boston, MA, USA.
⁷ Maxwell Finland Laboratories, Boston Medical Center, Boston, MA, USA; Department of Epidemiology, School of Public Health, Boston University, Boston, MA, USA; School of Medicine, Boston University, Boston, MA, USA.

PMID: 28645717
DOI: 10.1016/j.vaccine.2017.05.077

Abstract

Background: Following the introduction of pneumococcal conjugate vaccines (PCV), overall nasopharyngeal colonization rates have not changed significantly, however a dramatic and sustained decline in invasive pneumococcal disease (IPD) in children was observed in every setting where the PCVs were implemented. We aimed to describe the differences in invasive disease potential of serotypes that are common colonizers in pre- and post-vaccine eras in order to provide further insight in our understanding of dynamic epidemiology of pneumococcal diseases.

Methods: Using data from surveillance of nasopharyngeal carriage and enhanced surveillance for IPD, a serotype specific "invasive capacity (IC)" was computed by dividing the incidence of IPD due to serotype x by the carriage prevalence of that same serotype in children <7years of age in Massachusetts. We have evaluated the serotype specific invasive capacity in two periods; pre-PCV13 (2001/02, 2003/04, 2006/07, 2008/09) and post-PCV13 (2010/11 and 2013/14), and by age groups; <24monthsvs. ≥24months.

Results: An approximate 50-fold variation in the point estimate was observed between the serotypes having the highest (7F, 38, 19A, 3, 33F) and the lowest (6C, 35B, 21, 11A, 23B and 23A) computed serotype specific invasive disease potential. In the post-PCV13 era (6C, 35B, 11A, 23B and 23A), 5 of the 7 most common serotypes colonizing the nasopharynx were serotypes with the lowest invasive capacity. Serotype specific invasive capacity trended down in older children for majority of the serotypes, and serotypes 3, 10A and 19A had significantly lower invasive capacity in children older than 24months of age compared to younger children.

Conclusion: Invasive capacity differs among serotypes and likely by age. Point estimates of IC for most of the common serotypes colonizing children in Massachusetts in post-PCV13 era were low and likely explain the continued reduction in IPD from the pre-PCV era in the absence of specific protection against these serotypes.

Keywords: Carriage; Invasive disease potential; Serotype replacement.

MeSH terms

Adolescent
Bacteremia / epidemiology*
Bacteremia / microbiology
Carrier State / epidemiology*
Carrier State / microbiology
Child
Child, Preschool
Epidemiological Monitoring*
Female
Humans
Incidence
Infant
Infant, Newborn
Male
Massachusetts / epidemiology
Meningitis, Bacterial / epidemiology*
Meningitis, Bacterial / microbiology
Pneumococcal Infections / epidemiology*
Pneumococcal Infections / microbiology
Serogroup*
Streptococcus pneumoniae / classification*
Streptococcus pneumoniae / isolation & purification