Antibody concentrations against the infecting serotype in vaccinated and unvaccinated children with invasive pneumococcal disease in the United Kingdom, 2006-2013.
BACKGROUND
This study aimed to estimate, following invasive pneumococcal disease (IPD), the proportion of children with protective immunoglobulin G (IgG) concentrations against the infecting serotype compared with other vaccine serotypes, and to assess risk of recurrent IPD.


METHODS
Pneumococcal antibody concentrations were available for 413 children with vaccine-type IPD diagnosed during 2006-2013. We compared serotype-specific IgG concentrations against the infecting vs other vaccine serotypes, after adjusting for confounders such as age using multilevel analyses.


RESULTS
After IPD, a higher proportion of vaccine-naive children had IgG concentrations ≥0.35 µg/mL against their infecting serotype than other vaccine serotypes (51% vs 36%; P < .001). In contrast, among children immunized with pneumococcal conjugate vaccine (PCV) both before and after IPD, the proportion with IgG concentrations ≥0.35 µg/mL against the infecting serotype was lower compared with other vaccine serotypes (71% vs 98%; P < .001). These children also had lower IgG geometric mean concentrations (GMCs) against the infecting serotype (2.22 µg/mL) vs other vaccine serotypes (15.64 µg/mL) in multilevel models (IgG GMC ratio, 0.24; 95% confidence interval, .18-.32), although their IgG GMC was higher compared with vaccine-naive children. Vaccinated children with IgG concentrations <0.35 µg/mL against their infecting serotype generally remained unresponsive despite further vaccine doses. However, recurrent IPD with the same infecting serotype was rare (7/3030 children [0.2%]) and not associated with unresponsiveness.


CONCLUSIONS
Vaccination with PCV before and/or after IPD was associated with lower IgG concentrations against the infecting serotype compared with other vaccine serotypes, but recurrent IPD was rare. Further studies are needed to understand this phenomenon in immunized children.
Immunisation, Hepatitis and Blood Safety Department, Public Health England, London, United Kingdom Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, Trois-Rivières, Canada.
Nicholas
N
Brousseau
Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, Trois-Rivières, Canada.
Nick
N
Andrews
Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, Trois-Rivières, Canada.
Pauline
P
Waight
Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
Elaine
E
Stanford
Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
Emma
E
Newton
Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
Rachael
R
Almond
Department of Medicine, Griffith University, Southport, Queensland, Australia Institute of Hygiene and Microbiology, University of Würzburg, Germany.
Mary P E
MP
Slack
Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, Trois-Rivières, Canada.
Elizabeth
E
Miller
Vaccine Evaluation Unit, Public Health England, Manchester Royal Infirmary, United Kingdom.
Ray
R
Borrow
Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, Trois-Rivières, Canada.
Shamez N
SN
Ladhani
D000907:Antibodies, Bacterial / Q000097:blood*; D002675:Child, Preschool; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000276:immunology*; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology*; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D013296:Streptococcus pneumoniae / Q000276:immunology*; D006113:United Kingdom / Q000453:epidemiology
D000907:Antibodies, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D007074:Immunoglobulin G
immunization; immunoglobulin G; invasive pneumococcal disease; pneumococcal conjugate vaccine; vaccination