The impact of pneumococcal conjugate vaccines on serotype 19A nasopharyngeal carriage

ABSTRACT

Introduction: By preventing nasopharyngeal carriage acquisition among vaccinated persons, and thus reducing transmission, pneumococcal conjugate vaccines (PCVs) provide protection against pneumococcal vaccine serotypes among unvaccinated individuals. This systematic review assessed PCVs containing serotype 19A or cross-reactive 19F for 19A carriage effects.

Areas covered: Peer-reviewed literature was searched for manuscripts published between 1/1/2000 and 06/18/2018 assessing the impact of PCV on 19A carriage.

Expert opinion: Fifty-five, 12, and 32 articles were identified for PCV7, PCV10, and PCV13, respectively. In two of four PCV7 randomized controlled trials (RCTs), 19A carriage was significantly higher in PCV7-vaccinated vs control subjects; in two of two PCV10 RCTs, there was no significant difference in 19A carriage and acquisition between PCV10-vaccinated (2 + 1 schedule) vs control subjects, apart from one timepoint (3 + 1 schedule); and one of one RCTs of PCV13 showed significant decreases in 19A carriage and acquisition in PCV13- vs PCV7-vaccinated (3 + 1 schedule) children. These findings were consistent with observational studies in which an increase or no change in 19A carriage was observed in 91% and 67% of PCV7 and PCV10 studies, respectively, whereas 87% of PCV13 studies documented a decrease. Countries in which serotype 19A transmission is substantial should consider the use of vaccines containing serotype 19A.

KEYWORDS:

• Nasopharyngeal carriage
• pneumococcal conjugate vaccine
• serotype 19A
• serotype 19F

Article highlights

• The ability of pneumococcal conjugate vaccines (PCV) to provide indirect protection to unvaccinated populations is mediated by a reduction of vaccine-type—or in principle cross-reactive type—nasopharyngeal carriage.

• A literature search was conducted for peer-reviewed English language articles published between 1 January 2000 and 18 June 2018, focusing on randomized clinical trials and observational studies evaluating the impact of PCV7, PCV10 and PCV13 on serotype 19A carriage in countries with high vaccine uptake.

• Evidence does not support reduction in 19A carriage from vaccines containing serotype 19F but not containing serotype 19A.

• Consistent data from a large number of studies support the ability of PCV13, which contains serotype 19A, to reduce 19A carriage regardless of study design or vaccine schedule.

• Jurisdictions with substantial serotype 19A transmission, as measured by carriage or disease in vaccinated or unvaccinated age cohorts, should consider use of serotype 19A-containing PCVs.

• The ability of potentially cross-reactive serotypes to protect against disease or carriage likely is specific to individual serotypes and thus requires a case-by-case evaluation.

Declaration of interest

M Tin Tin Htar, L Jodar, H L Sings, M Syrochkina, B Taysi, B Hilton, H-J Schmitt and B D Gessner are all employees of Pfizer Inc. and may hold stock or stock options. Editorial/medical writing support was provided by Scott Vuocolo, PhD, at Pfizer Inc. (Collegeville, PA), and Tricia Newell, PhD and Jill E Kolesar, PhD, at Complete Healthcare Communications, LLC (North Wales, PA), a CHC Group Company, and was funded by Pfizer Inc. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has disclosed that they worked as a consultant for GlaxoSmithKline vaccines Malaria vaccine group between 2014 and 2017.

Additional information

Funding

This work was sponsored by Pfizer Inc.