Retrospective Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Pediatr. Aug 8, 2016; 5(3): 311-318
Published online Aug 8, 2016. doi: 10.5409/wjcp.v5.i3.311
Potential carrier priming effect in Australian infants after 7-valent pneumococcal conjugate vaccine introduction
Mohamed Tashani, Sanjay Jayasinghe, Zitta B Harboe, Harunor Rashid, Robert Booy
Mohamed Tashani, Sanjay Jayasinghe, Harunor Rashid, Robert Booy, National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, the Children’s Hospital at Westmead, Sydney 2145, Australia
Mohamed Tashani, Sanjay Jayasinghe, Harunor Rashid, Robert Booy, the Discipline of Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney 2145, Australia
Zitta B Harboe, Neisseria and Streptococcus Reference Laboratory, Department of Microbiology and Infection Control, Statens Serum Institut, 2100 Copenhagen, Denmark
Harunor Rashid, Robert Booy, Marie Bashir Institute for Infectious Diseases and Biosecurity, School of Biological Sciences and Sydney Medical School, University of Sydney, Sydney 2006, Australia
Robert Booy, World Health Organization Collaborating Centre for Mass Gatherings and High Consequence/High Visibility Events, Flinders University, Adelaide 5001, Australia
Author contributions: All authors contributed equally to this manuscript; Booy R contributed to conceptualizing the idea; Tashani M conducted the literature review and performed data collection and analysis; Jayasinghe S provided support in accessing, collecting and analysing the data; Harboe ZB provided additional data from overseas; and Rashid H helped in writing and revision of this manuscript; the authors have seen and agreed to the submitted version of the paper, that all who have been acknowledged as contributors have agreed to their inclusion.
Institutional review board statement: Access to data was obtained by a formal permission of the Department of Health and Ageing and the Australian Capital Territory Health Human Research Ethics Committee, approval reference number (ETHLR.13.318).
Informed consent statement: Patients were not required to give informed consent to the study because the analysis used anonymous clinical data.
Conflict-of-interest statement: Professor Robert Booy has received funding from Baxter, CSL, GSK, Merck, Novartis, Pfizer, Roche, Romark and Sanofi Pasteur for the conduct of sponsored research, travel to present at conferences or consultancy work; all funding received is directed to research accounts at the Children’s Hospital at Westmead; Dr Harunor Rashid has received fees from Pfizer and Novartis for consulting or serving on an advisory board; the other authors have declared no conflict of interest in relation to this work.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Mohamed Tashani, DCH, MBBCH, MPH, MHM, MIPH, National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, the Children’s Hospital at Westmead, Locked Bag 4001, Sydney 2145, Australia.
Telephone: +61-29-8451232 Fax: +61-29-8451418
Received: May 19, 2016
Peer-review started: May 20, 2016
First decision: June 6, 2016
Revised: July 12, 2016
Accepted: July 20, 2016
Article in press: July 22, 2016
Published online: August 8, 2016

AIM: To investigate evidence of clinical protection in infants after one dose of 7-valent pneumococcal conjugate vaccine (7vPCV) owing to carrier priming.

METHODS: Using Australian National Notifiable Diseases Surveillance System data, we conducted a descriptive analysis of cases of vaccine type invasive pneumococcal disease (VT-IPD) during “catch-up” years, when 7vPCV was carrier primed by prior administration of DTPa vaccine. We compared the number of VT-IPD cases occurring 2-9 wk after a single dose of 7vPCV (carrier primed), with those < 2 wk post vaccination, when no protection from 7vPCV was expected yet. Further comparison was conducted to compare the occurrence of VT-IPD cases vs non-VT-IPD cases after a single carrier-primed dose of 7vPCV.

RESULTS: We found four VT-IPD cases occurring < 2 wk after one carrier primed dose of 7vPCV while only one case occurred 2-9 wk later. Upon further comparison with the non-VT-IPD cases that occurred after one carrier primed dose of 7vPCV, two cases were detected within 2 wk, whereas seven occurred within 2-9 wk later; suggesting a substantial level of protection from VT-IPD occurring from 2 wk after carrier-primed dose of 7vPCV.

CONCLUSION: This data suggest that infants may benefit from just one dose of 7vPCV, likely through enhanced immunity from carrier priming effect. If this is proven, an adjusted 2-dose schedule (where the first dose of PCV is not given until after DTPa) may be sufficient and more cost-effective.

Keywords: Carrier priming, Conjugate vaccine, Infant, Invasive pneumococcal disease

Core tip: With the inclusion of newer conjugate vaccines with higher number of serotypes in the immunisation schedule, literature suggests that prior immunisation with tetanus/diphtheria-containing vaccines could enhance the immunogenicity of subsequently administered glycoconjugate vaccine, a phenomenon known as “carrier priming”. This analysis provides evidence of substantial clinical protection ensued after one dose of 7-valent pneumococcal conjugate vaccine as result of carrier priming. This phenomenon could be implemented to enhance the immunogenicity of conjugate vaccines among vulnerable populations such as infants in resource-poor settings, travellers, immigrants and refugees.