The high prevalence and impact of rheumatic heart disease in pregnancy in First Nations populations in a high-income setting: a prospective cohort study.

OBJECTIVE: To describe the epidemiology of rheumatic heart disease (RHD) in pregnancy in Australia and New Zealand (A&NZ). DESIGN: Prospective population-based study. SETTING: Hospital-based maternity units throughout A&NZ. POPULATION: Pregnant women with RHD with a birth outcome of ≥20 weeks of gestation between January 2013 and December 2014. METHODS: We identified eligible women using the Australasian Maternity Outcomes Surveillance System (AMOSS). De-identified antenatal, perinatal and postnatal data were collected and analysed. MAIN OUTCOME MEASURES: Prevalence of RHD in pregnancy. Perinatal morbidity and mortality. RESULTS: There were 311 pregnancies associated with women with RHD (4.3/10 000 women giving birth, 95% CI 3.9-4.8). In Australia, 78% were Aboriginal or Torres Strait Islander (60.4/10 000, 95% CI 50.7-70.0), while in New Zealand 90% were Maori or Pasifika (27.2/10 000, 95% CI 22.0-32.3). One woman (0.3%) died and one in ten was admitted to coronary or intensive care units postpartum. There were 314 births with seven stillbirths (22.3/1000 births) and two neonatal deaths (6.5/1000 births). Sixty-six (21%) live-born babies were preterm and one in three was admitted to neonatal intensive care or special care units. CONCLUSION: Rheumatic heart disease in pregnancy persists in disadvantaged First Nations populations in A&NZ. It is associated with significant cardiac and perinatal morbidity. Preconception planning and counselling and RHD screening in at-risk pregnant women are essential for good maternal and baby outcomes. TWEETABLE ABSTRACT: Rheumatic heart disease in pregnancy persists in First Nations people in Australia and New Zealand and is associated with major cardiac and perinatal morbidity.

Environmental and social determinants of acute rheumatic fever: a longitudinal cohort study.

Acute rheumatic fever (ARF), an auto-immune response to a group A Streptococcus infection and precursor to rheumatic heart disease (RHD), remains endemic in many socio-economically disadvantaged settings. A Global Resolution on ARF and RHD was recently adopted at the 71st World Health Assembly where governments committed to improving efforts to prevent and control ARF and RHD. To inform these efforts, the objectives of this study were to examine associations between childhood ARF in the UK between 1958 and 1969 and a range of environmental and social factors. Of 17 416 children from the nationally representative birth cohort of the National Child Development Study, ARF was reported in 23 children during early childhood (between birth and the 7-year follow-up) and in 29 additional children during middle childhood (between the 7- and 11-year follow-ups). Risk factors associated with ARF in both early and middle childhood were: a large family size; attendance at a private nursery or class; a history of nephritis, kidney or urinary tract infections; and a history of throat or ear infections. Risk factors for ARF in early childhood alone were families with fathers in a professional or semi-professional occupation and families who moved out of their local neighbourhood. Risk factors in late childhood alone included overcrowding and free school meals. These data suggest that prevention strategies in ARF endemic settings may be enhanced by targeting, for example, new members entering a community and children in environments of close contact, such as a nursery or shared bedrooms.

The fall and rise of Group A Streptococcus diseases.

Streptococcus pyogenes (or Group A Streptococcus, GAS) is a Gram-positive human pathogen responsible for a diverse array of superficial, invasive and immune-related diseases. GAS infections have historically been diseases of poverty and overcrowding, and remain a significant problem in the developing world and in disadvantaged populations within developed countries. With improved living conditions and access to antibiotics, the rates of GAS diseases in developed societies have gradually declined during the 20th century. However, genetic changes in circulating GAS strains and/or changes in host susceptibility to infection can lead to dramatic increases in the rates of specific diseases. No situations exemplify this more than the global upsurge of invasive GAS disease that originated in the 1980s and the regional increases in scarlet fever in north-east Asia and the UK. In each case, increased disease rates have been associated with the emergence of new GAS strains with increased disease-causing capability. Global surveillance for new GAS strains with increased virulence is important and determining why certain populations suddenly become susceptible to circulating strains remains a research priority. Here, we overview the changing epidemiology of GAS infections and the genetic alterations that accompany the emergence of GAS strains with increased capacity to cause disease.

Whole genome sequencing reveals extensive community-level transmission of group A Streptococcus in remote communities.

Impetigo is common in remote Indigenous children of northern Australia, with the primary driver in this context being Streptococcus pyogenes [or group A Streptococcus (GAS)]. To reduce the high burden of impetigo, the transmission dynamics of GAS must be more clearly elucidated. We performed whole genome sequencing on 31 GAS isolates collected in a single community from children in 11 households with ⩾2 GAS-infected children. We aimed to determine whether transmission was occurring principally within households or across the community. The 31 isolates were represented by nine multilocus sequence types and isolates within each sequence type differed from one another by only 0-3 single nucleotide polymorphisms. There was evidence of extensive transmission both within households and across the community. Our findings suggest that strategies to reduce the burden of impetigo in this setting will need to extend beyond individual households, and incorporate multi-faceted, community-wide approaches.

Changes in the clinical and epidemiological features of group A streptococcal bacteraemia in Australia's Northern Territory.

OBJECTIVE: Invasive group A streptococcus (iGAS) disease is an important cause of mortality globally. The incidence of iGAS in Australia's tropical Northern Territory (NT) has been previously reported as 32.2/100 000 in Indigenous people for the period 1991-1996. We aimed to measure the incidence and severity of iGAS disease in the NT since this time. METHODS: We collected demographic data for all GAS blood culture isolates over a 12-year period (1998-2009) from the three hospital laboratories serving the tropical NT. We then collected detailed clinical information from hospital records and databases for the subset of these patients who were admitted to Royal Darwin Hospital during 2005-2009. RESULTS: There were 295 confirmed cases of GAS bacteraemia over the study period, with a mean (SD) age of 42.1 (22.0) years, and 163 (55.0%) were male. The annual age-adjusted incidence was 15.2 (95% CI 13.4-16.9)/100 000 overall and 59.4 (95% CI 51.2-67.6) in Indigenous Australians. For 2005-2009, there were 123 cases with the most common focus of infection being skin/soft tissue [44 (35.6%)]; 29 patients (23.6%) required intensive care unit admission and 20 (16.3%) had streptococcal toxic shock syndrome. Antecedent sore throat or use of non-steroidal anti-inflammatory drugs was rare, but current or recent scabies, pyoderma and trauma were common. CONCLUSION: The incidence and severity of iGAS are high and increasing in tropical northern Australia, and urgent attention is needed to improve surveillance and the social determinants of health in this population. This study adds to emerging data suggesting increasing importance of iGAS in low- and middle-income settings globally.

Nitazoxanide for the treatment of infectious diarrhoea in the Northern Territory, Australia 2007-2012.

INTRODUCTION: Australian Indigenous children suffer a high burden of diarrhoeal disease. Nitazoxanide is an antimicrobial that has been shown to be effective against a broad range of enteropathogens. To date, its use has not been reported in the tropical Top End (northernmost part) of the Northern Territory, Australia. The objective was to describe the use of nitazoxanide at the Royal Darwin Hospital, Northern Territory, and to assess any association with the time to resolution of diarrhoea. METHODS: Eligible children (≤13 years) were identified from dispensary records as having been prescribed nitazoxanide during the audit period, 1 July 2007 to 31 March 2012. Patient demographics, symptoms, diarrheal aetiology, treatment details and clinical outcomes were obtained by chart review. RESULTS: Twenty-eight children were treated with nitazoxanide, mostly for Cryptosporidium infection associated with prolonged diarrhoea. Dehydration was evident in 27 (96%) children on admission, and 11 (41%) were underweight. Diarrhoeal duration prior to treatment was 11.5 days (6.5 days pre- and 5 days post-admission). For children ≥12 months, nitazoxanide was prescribed according to guidelines stipulated by the Centers for Disease Control and Prevention (CDC). Resolution of diarrhoea occurred a median of 2.4 days (IQR: 1.4-7.3) after starting treatment. An increase in weight for length at discharge was found for all children. CONCLUSIONS: Prompt resolution of diarrhoea without adverse outcomes suggests nitazoxanide may be an effective treatment for Cryptosporidium infection in this setting. Its role in the treatment of other causes of infectious diarrhoea needs further investigation. Randomised trials will further direct its use and determine optimal dosing regimens.

Case-control evaluation of the effectiveness of the G1P[8] human rotavirus vaccine during an outbreak of rotavirus G2P[4] infection in central Australia.

UNLABELLED: The human rotavirus vaccine was evaluated during an outbreak of rotavirus G2P[4] infection in central Australia. No overall protective effect against hospitalization was demonstrated, raising concerns over the durability of vaccine protection against heterotypic strains. BACKGROUND: Two and a half years after commencing routine vaccination with human rotavirus vaccine, an outbreak of rotavirus G2P[4] infection occurred in central Australia. Vaccine effectiveness against a P[8]-containing strain (G9P[8]) had been demonstrated previously in this setting. This subsequent outbreak provided the opportunity to evaluate vaccine effectiveness against hospitalizations for a non-vaccine-related genotype in the same population. METHODS: A case-control study was nested within a cohort of vaccine-eligible children listed on a population-based immunization register. Children with rotavirus-confirmed gastroenteritis were individually matched by date of birth and Indigenous status with 4 control subjects. RESULTS: Forty-one cases met the inclusion criteria, and 21 were severe cases among infants aged <12 months. Nineteen (46%) of 41 case patients had received 2 doses of human rotavirus vaccine, compared with 87 (53%) of 164 control subjects. Vaccine effectiveness against rotavirus-related hospitalization was 19% (odds ratio, .81; 95% confidence interval, .32-2.05) for 2 doses compared with none. On secondary analysis, there was evidence of a protective effect against disease complicated by acidosis in the subset of infants aged <12 months (odds ratio, .15; 95% confidence interval, .03-.84). CONCLUSIONS: Evidence was not found for an overall protective effect of human rotavirus vaccine against hospitalization for rotavirus disease in this setting. Post hoc analyses suggested a protective effect against severe disease in young infants.

High incidence of Haemophilus influenzae type b infection in children in Pacific island countries.

The Haemophilus influenzae type b (Hib) disease burden among children <5 years old in 4 Pacific island countries (PICs) was estimated. The incidence of confirmed Hib meningitis was calculated using the numbers of culture-confirmed isolates. In addition, the World Health Organization (WHO) Hib Rapid Assessment Tool (RAT) was used to estimate the true Hib meningitis incidence and the number of Hib meningitis and pneumonia cases, as well as the number of deaths due to Hib meningitis and pneumonia. The Hib meningitis annual incidence in 3 PICs was 70-84 cases per 100,000 children <5 years old. For PICs, the RAT is likely to overestimate the Hib pneumonia burden, as it assumes a 5 : 1 ratio of Hib pneumonia to Hib meningitis. The true ratio is likely to be 1 : 1. The high Hib disease burden and the relative cost-effectiveness of Hib vaccine make the introduction of Hib vaccine a good investment for PICs, costing US1000 dollars-US10,000 dollars for each death prevented--a number that ignores savings from reductions in the cost of treatment.

Success of a scabies control program in an Australian aboriginal community.

OBJECTIVE: To adapt, implement and evaluate a model of scabies control in an Australian Aboriginal community. METHODS: After initially examining the population, we offered all residents treatment with 5% permethrin cream. Visits were made during the ensuing 25 months to rescreen and to treat new-cases of scabies and contacts. RESULTS: The prevalence of scabies was reduced from 28.8% before the program to < 10% during the entire period (from 32.3% to < 10% in children) (P < 0.01 for each visit). The initial prevalence of pyoderma in children was 69.4%, which was reduced and maintained at approximately one-half that rate during the last 16 months (P < 0.004 for the last 4 visits). Residual pyoderma in children was significantly less severe and no longer scabies-related. CONCLUSIONS: This simplified model of scabies control had a substantial effect on scabies prevalence and on pyoderma prevalence and severity which was sustained for > 2 years. It could prove useful for other communities with high rates of scabies and pyoderma.

Randomized, controlled trial comparing once daily and three times daily gentamicin in children with urinary tract infections.

OBJECTIVE: To undertake population pharmacokinetic modeling and to determine the safety and efficacy of once daily (OD) gentamicin dosing in children with severe urinary tract infections (UTI). METHODS: An open, randomized, controlled trial comparing OD with three times daily (TD) gentamicin dosing in hospitalized children ages 1 month to 12 years with UTI. Daily doses (milligrams per kg per day) of gentamicin in both groups were 7.5 (<5 years old), 6.0 (5 to 10 years old) and 4.5 (>10 years old). RESULTS: There were 179 children enrolled (90 OD, 89 TD). Baseline clinical characteristics and pathogens were similar, except that circulatory compromise and renal cortical scintigraphic defects were more common in the OD group. Median gentamicin treatment durations were 3.0 (OD) and 2.7 (TD) days. Mean peak gentamicin concentrations were 17.3 (OD) vs. 6.4 (TD) mg/l; 99% of peak concentrations were >7 mg/l in the OD group whereas 16% of peak concentrations were <5 mg/l in the TD group. Mean trough concentrations were 0.35 (OD) vs. 0.55 (TD) mg/l. In the OD group 4% of trough concentrations were > or = 2 mg/l, whereas in the TD group only 0.7% were > or = 2 mg/l. Age or prior elevated peak concentrations did not predict high trough concentrations. Population pharmacokinetic modeling of the data fitted a one-compartment model with first order elimination. There were no clinical or bacteriologic failures. The two disease-related complications were confined to the OD group. No nephro- or ototoxicity was identified. CONCLUSIONS: With age-appropriate dosing and measurement of serum trough concentrations before the second dose, OD gentamicin is safe and effective for the treatment of UTI requiring parenteral treatment in children aged 1 month to 12 years.

Disseminated, multiclonal Epstein-Barr virus-associated lymphoproliferative disease in a patient with hematological and immunological anomalies. Molecular analysis correlates with morphological appearance.

We report a case of a 21-year-old woman with hematopoietic, immunological, and congenital dysmorphic abnormalities, who died following rapidly progressive, disseminated Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD). Polymerase chain reaction (PCR) amplification of formalin-fixed paraffin-embedded tissue showed differences in the clonality of each separate lymphoproliferative lesion examined, as determined by immunoglobulin heavy chain (IgH) gene rearrangement. PCR analysis also demonstrated that all lesions contained EBV genome. Since DNA had been extracted from paraffin blocks, a direct comparison of morphology and clonality could be made in each individual lesion. The evidence from this study indicates that the monoclonal tumors arose de novo in multiple sites and that the polyclonal background observed in some lesions reflected a substantial concomitant inflammatory response.

Ability of clinical isolates of group A streptococci to adhere to and invade HEp-2 epithelial cells.

Individual strains of group A streptococci (GAS) differ in virulence, but the reasons for these differences are incompletely understood. To determine if the ability of GAS to cause invasive disease corresponded with their capacity to adhere to or invade epithelial cells, 63 clinical isolates of GAS (40 from patients with systemic infection and 23 from superficial disease) were examined in quantitative assays of bacterial adhesion to and invasion of HEp-2 cells, a continuous line of human pharyngeal epithelial cells. The results showed that individual isolates of GAS varied considerably in their ability to adhere to and penetrate HEp-2 cells. However, on the whole, strains from patients with invasive disease adhered to cells in numbers c.1.5 greater than those from superficial infection. Paradoxically, strains from patients with invasive disease invaded HEp-2 cells to a significantly lesser extent than those from superficial sites, with a two-fold difference in invasion index (defined as the percentage of cell-associated bacteria located intracellularly). To determine if these differences were caused by differences in the production of hyaluronic acid capsule or M protein by the two groups of bacteria, the adherence and invasive capacities of bacteria carrying defined mutations in the genes for these factors were examined. Although M6-protein-deficient [corrected] bacteria were less adherent to HEp-2 cells than the wild-type, neither the hyaluronic acid capsule nor the M protein had a significant influence on the ability of GAS to adhere to or invade HEp-2 cells. The results of this study demonstrate that there are biological differences between GAS isolates associated with invasive and superficial diseases and that these differences can be demonstrated by an assay of bacterial adherence to and invasion of HEp-2 epithelial cells.

Mortality due to acute rheumatic fever and rheumatic heart disease in the Northern Territory: a preventable cause of death in aboriginal people.

OBJECTIVE: To determine the death rates and effect on premature mortality in the Northern Territory of acute rheumatic fever and rheumatic heart disease. METHODS: We ascertained deaths due to acute rheumatic fever and rheumatic heart disease for the period 1979-96 from death certificates, a database of all patients with these diseases and mortuary records. Crude and age-standardised death rates were calculated, as were years of potential life lost before age 65, between 15 and 65, and before age 70. RESULTS: Of 182 deaths, 171 (94%) were in Aboriginal people. The mean age at death of Aboriginal people was 35.7 years, compared to 67.3 years in non-Aboriginal people. The age-standardised death rate in Aboriginal people was 30.2 per 100,000 person-years, compared to 1.1 in non-Aboriginal people. Acute carditis caused 13 deaths at a mean age of 14.2 years. Mortality in Aboriginal people was highest in the > 30 age groups and in females. Premature mortality for Aboriginal people was more than four times that from developing countries. CONCLUSIONS: Acute rheumatic fever and rheumatic heart disease are not only common in Aboriginal people, they affect and often kill people in their most productive years. A co-ordinated control program should help in the short term, but will not address underlying causes of these and other preventable diseases.

Echocardiographic screening in a resource poor setting: borderline rheumatic heart disease could be a normal variant.

OBJECTIVE: To estimate the echocardiography confirmed prevalence of rheumatic heart disease (RHD) in school children in Fiji. DESIGN: Cross-sectional observational study. SETTING: Ten primary schools in Fiji. PATIENTS: School children aged 5-14 years. INTERVENTIONS: Each child had an echocardiogram performed by an echocardiographic technician subsequently read by a paediatric cardiologist not involved with field screening, and auscultation performed by a paediatrician. MAIN OUTCOME MEASURES: Echocardiographic criteria for RHD diagnosis were based on those previously published by the National Institutes of Health (NIH) and World Health Organization (WHO), and data were also analyzed using the new World Heart Federation (WHF) criteria. Prevalence figures were calculated with binomial 95% confidence intervals. RESULTS: Using the modified NIH/WHO criteria the prevalence of definite RHD prevalence was 7.2 cases per 1000 (95% CI 3.7-12.5), and the prevalence of probable RHD 28.2 cases per 1000 (95% CI 20.8-37.3). By applying the WHF criteria the prevalence of definite and borderline RHD was 8.4 cases per 1000 (95% CI 4.6-14.1) and 10.8 cases per 1000 (95% CI 6.4-17.0) respectively. Definite RHD was more common in females (OR 5.1, 95% CI 1.1-48.3) and in children who attended school in a rural location (OR 2.3, 95% CI 0.6-13.50). Auscultation was poorly sensitive compared to echocardiography (30%). CONCLUSION: There is a high burden of undiagnosed RHD in Fiji. Auscultation is poorly sensitive when compared to echocardiography in the detection of asymptomatic RHD. The results of this study highlight the importance of the use of highly sensitive and specific diagnostic criteria for echocardiography diagnosis of RHD.

Updated model of group A Streptococcus M proteins based on a comprehensive worldwide study.

Group A Streptococcus (GAS) M protein is an important virulence factor and potential vaccine antigen, and constitutes the basis for strain typing (emm-typing). Although >200 emm-types are characterized, structural data were obtained from only a limited number of emm-types. We aim to evaluate the sequence diversity of near-full-length M proteins from worldwide sources and analyse their structure, sequence conservation and classification. GAS isolates recovered from throughout the world during the last two decades underwent emm-typing and complete emm gene sequencing. Predicted amino acid sequence analyses, secondary structure predictions and vaccine epitope mapping were performed using MUSCLE and Geneious software. A total of 1086 isolates from 31 countries were analysed, representing 175 emm-types. emm-type is predictive of the whole protein structure, independent of geographical origin or clinical association. Findings of an emm-type paired with multiple, highly divergent central regions were not observed. M protein sequence length, the presence or absence of sequence repeats and predicted secondary structure were assessed in the context of the latest vaccine developments. Based on these global data, the M6 protein model is updated to a three representative M protein (M5, M80 and M77) model, to aid in epidemiological analysis, vaccine development and M protein-related pathogenesis studies.

Preliminary validation of a novel high-resolution melt-based typing method based on the multilocus sequence typing scheme of Streptococcus pyogenes.

The major limitation of current typing methods for Streptococcus pyogenes, such as emm sequence typing and T typing, is that these are based on regions subject to considerable selective pressure. Multilocus sequence typing (MLST) is a better indicator of the genetic backbone of a strain but is not widely used due to high costs. The objective of this study was to develop a robust and cost-effective alternative to S. pyogenes MLST. A 10-member single nucleotide polymorphism (SNP) set that provides a Simpson's Index of Diversity (D) of 0.99 with respect to the S. pyogenes MLST database was derived. A typing format involving high-resolution melting (HRM) analysis of small fragments nucleated by each of the resolution-optimized SNPs was developed. The fragments were 59-119 bp in size and, based on differences in G+C content, were predicted to generate three to six resolvable HRM curves. The combination of curves across each of the 10 fragments can be used to generate a melt type (MelT) for each sequence type (ST). The 525 STs currently in the S. pyogenes MLST database are predicted to resolve into 298 distinct MelTs and the method is calculated to provide a D of 0.996 against the MLST database. The MelTs are concordant with the S. pyogenes population structure. To validate the method we examined clinical isolates of S. pyogenes of 70 STs. Curves were generated as predicted by G+C content discriminating the 70 STs into 65 distinct MelTs.

Serotype-specific avidity is achieved following a single dose of the 7-valent pneumococcal conjugate vaccine, and is enhanced by 23-valent pneumococcal polysaccharide booster at 12 months.

AIM: To evaluate whether the avidity of serotype-specific IgG to pneumococcal serotypes is enhanced by an increased number of doses of the 7-valent pneumococcal conjugate vaccine (PCV) in infancy or by a 12 month 23-valent pneumococcal polysaccharide vaccine (23vPPS) booster, and/or subsequent re-exposure to a small dose of pneumococcal polysaccharide antigens (mPPS) at 17 months. METHODS: Fijian infants aged 6 weeks were recruited, stratified by ethnicity and randomized to 8 groups to receive 0, 1, 2, or 3 doses of PCV, with or without 23vPPS at 12 months. All children received mPPS at 17 months of age. Avidity of serotype-specific IgG for PCV serotypes in the first 12 months and for all 23vPPS serotypes thereafter was assessed by EIA after sodium thiocyanate elution. RESULTS: At one month post primary series, the 2 and 3 PCV dose groups demonstrated similar avidity, with the single dose group tending to have lower avidity. However, by age 9 months, the single dose group had similar avidity to the 2 and 3 PCV groups for most serotypes. The 23vPPS booster enhanced affinity maturation for most serotypes and this was most marked in those groups that received a single PCV dose. There was little further increase following the mPPS. CONCLUSIONS: By 9 months of age, similar avidity can be induced following one, 2 or 3 doses of PCV. A 23vPPS booster at 12 months enhanced affinity maturation with an increase in antibody avidity for most serotypes. Subsequent re-challenge with mPPS at 17 months did not further enhance the avidity of serotype-specific response in the 12 month 23vPPS groups.

Opsonophagocytic activity following a reduced dose 7-valent pneumococcal conjugate vaccine infant primary series and 23-valent pneumococcal polysaccharide vaccine at 12 months of age.

Opsonophagocytic activity (OPA) was measured following reduced infant doses of 7-valent pneumococcal conjugate vaccine (PCV-7) with or without 23-valent pneumococcal polysaccharide vaccine (PPV-23) at 12 months, and subsequent re-exposure to a small dose of pneumococcal polysaccharide antigens (mPPS) at 17 months. Fijian infants were randomized to receive 0, 1, 2, or 3 PCV-7 doses. Half received PPV-23 at 12 months and all received mPPS at 17 months. OPA was performed on up to 14 serotypes. Three and 2 PCV-7 doses resulted in similar OPA for most PCV-7 serotypes up to 9 months and for half of the serotypes at 12 months. A single dose improved OPA compared with the unvaccinated group. PPV-23 significantly improved OPA for all serotypes tested but in general, was associated with diminished responses following re-challenge.

Hyporesponsiveness to re-challenge dose following pneumococcal polysaccharide vaccine at 12 months of age, a randomized controlled trial.

BACKGROUND: To evaluate the immunological impact of the 23-valent pneumococcal polysaccharide vaccine (23vPPS) at 12 months, for children who have received zero to three infant doses of seven-valent pneumococcal conjugate vaccine (PCV), on responses to a subsequent exposure to a small dose of 23vPPS (mPPS). METHODS: Five hundred and fifty-two Fijian infants were stratified by ethnicity and randomized into eight groups to receive zero, one, two, or three PCV doses at 14 weeks, six and 14 weeks, or six, ten, and 14 weeks. Within each group, half received 23vPPS at 12 months and all received mPPS at 17 months. Sera were taken prior and one month post-mPPS. FINDINGS: By 17 months, geometric mean antibody concentrations (GMC) to all 23 serotypes in 23vPPS were significantly higher in children who had received 23vPPS at 12 months compared to those who had not. Post-mPPS, children who had not received the 12 month 23vPPS had a significantly higher GMC for all PCV serotypes compared with those who had (each p<0.02). For the non-PCV serotypes, children who had not received the 12 month 23vPPS had significantly higher GMC for six of 16 non-PCV serotypes (7F, 9N, 12F, 19A, 22F, 33F) than those who did (each p<0.02). After adjusting for the pre-mPPS level, exposure to 23vPPS was associated with a lower response to mPPS for all serotypes (each p<0.001). INTERPRETATION: Despite higher antibody concentrations at 17 months in children who had received 23vPPS at 12 months, the response to a re-challenge was poor for all 23 serotypes compared to children who had not received the 12 month 23vPPS.