Pneumococcal conjugate vaccine (PCV) was introduced in the United Kingdom immunization schedule in September 2006. This study was conducted to establish the immunogenicity of licensed PCV (Prevenar) at a reduced, 2 priming dose schedule (2+1) and to evaluate functional responses in the context of vaccine effectiveness.
Infants were randomized to receive PCV at 2 and 3 months or 2 and 4 months of age. Boosters were administered at the same time as Haemophilus influenzae type B/meningococcal C conjugate and Measles, Mumps and Rubella or with Measles, Mumps and Rubella alone (www.ClinicalTrials.gov NCT00197808).
PCV at 2/3 months of age was poorly immunogenic and recruitment to this arm was terminated. PCV at 2/4 months of age resulted in lower than expected responses to serotypes 6B and 23F. Functional analysis of serotype 6B by OPA revealed that an enzyme-linked immunosorbent assay cutoff of 0.2 μg/mL was a better predictor of OPA positivity than a cut off of 0.35 μg/mL. PCV booster responses were excellent and no interference from concomitant vaccines was noted.
An interval of at least 8 weeks is required when starting PCV vaccination at 2 months of age although not all serotypes are equally immunogenic. Correlates of protection derived from enzyme-linked immunosorbent assay values may not be equally appropriate for all serotypes as illustrated by results for 6B in this study.
From the *Immunobiology Unit, UCL Institute of Child Health, London, United Kingdom; and †Centre for Infections, Health Protection Agency, Colindale, London, United Kingdom.
Accepted for publication October 16, 2009.
Supported by the Policy Research Program in the Department of Health, RDD grant 039/031, and also by the Department of Health Research and Development Directorate grant 039/031.
The views expressed are not necessarily those of the Department of Health.
Address for correspondence: David Goldblatt, MD, PhD, Immunobiology Unit, Institute of Child Health, 30 Guilford St, London WC1N 1EH, United Kingdom. E-mail: firstname.lastname@example.org.
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