Pneumococcal carriage, serotype distribution, and antimicrobial susceptibility in Papua New Guinean children vaccinated with PCV10 or PCV13 in a head-to-head trial.

BACKGROUND: Children in Papua New Guinea (PNG) are at high risk of pneumococcal infections. We investigated pneumococcal carriage rates, serotype distribution, and antimicrobial susceptibility in PNG children after vaccination with 10-valent or 13-valent pneumococcal conjugate vaccines (PCV10; PCV13). METHODS: Infants (N = 262) were randomized to receive 3 doses of PCV10 or PCV13 at 1-2-3 months of age, followed by pneumococcal polysaccharide vaccination (PPV) or no PPV at 9 months of age. Nasopharyngeal swabs (NPS) collected at ages 1, 4, 9, 10, 23 and 24 months were cultured using standard bacteriological procedures. Morphologically distinct Streptococcus pneumoniae colonies were serotyped by the Quellung reaction. Antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion and minimum inhibitory concentration (MIC). RESULTS: S. pneumoniae was isolated from 883/1063 NPS collected at 1-23 months of age, including 820 serotypeable (64 different serotypes) and 144 non-serotypeable isolates. At age 23 months, 93.6% (95%CI 86.6-97.6%) of PCV10 recipients and 88.6% (95%CI 80.1-94.4%) of PCV13 recipients were pneumococcal carriers, with higher carriage of PCV10 serotypes by PCV10 recipients (19.8%, 95%CI 12.2-29.5) than PCV13 recipients (9.3%, 95%CI 4.1-17.3) (p = 0.049). There were no other statistically significant differences between PCV10 and PCV13 recipients and children receiving PPV or no PPV. Nearly half (45.6%) of carried pneumococci were non-susceptible to penicillin based on the meningitis breakpoint (MIC ≥ 0.12 µg/mL), but resistance was rare (1.1%) using the non-meningitis cut-off (MIC ≥ 8 µg/mL). Non-susceptibility to trimethoprim-sulfamethoxazole (SXT) was common: 23.2% of isolates showed intermediate resistance (MIC 1/19-2/38 µg/mL) and 16.9% full resistance (MIC ≥ 4/76 µg/mL). PCV serotypes 14 and 19A were commonly non-susceptible to both penicillin (14, 97%; 19A, 70%) and SXT (14, 97%; 19A, 87%). CONCLUSION: Even after PCV10 or PCV13 vaccination, children living in a high-risk setting such as PNG continue to experience high levels of pneumococcal colonization, including carriage of highly antimicrobial-resistant PCV serotypes. The study is registered with ClinicalTrials.gov (CTN NCT01619462).

Distinct Streptococcus pneumoniae cause invasive disease in Papua New Guinea.

Streptococcus pneumoniae is a key contributor to childhood morbidity and mortality in Papua New Guinea (PNG). For the first time, whole genome sequencing of 174 isolates has enabled detailed characterisation of diverse S. pneumoniae causing invasive disease in young children in PNG, 1989-2014. This study captures the baseline S. pneumoniae population prior to the introduction of 13-valent pneumococcal conjugate vaccine (PCV13) into the national childhood immunisation programme in 2014. Relationships amongst lineages, serotypes and antimicrobial resistance traits were characterised, and the population was viewed in the context of a global collection of isolates. The analyses highlighted adiverse S. pneumoniae population associated with invasive disease in PNG, with 45 unique Global Pneumococcal Sequence Clusters (GPSCs) observed amongst the 174 isolates reflecting multiple lineages observed in PNG that have not been identified in other geographic locations. The majority of isolates were from children with meningitis, of which 52% (n=72) expressed non-PCV13 serotypes. Over a third of isolates were predicted to be resistant to at least one antimicrobial. PCV13 serotype isolates had 10.1 times the odds of being multidrug-resistant (MDR) compared to non-vaccine serotype isolates, and no isolates with GPSCs unique to PNG were MDR. Serotype 2 was the most commonly identified serotype; we identified a highly clonal cluster of serotype 2 isolates unique to PNG, and a distinct second cluster indicative of long-distance transmission. Ongoing surveillance, including whole-genome sequencing, is needed to ascertain the impact of the national PCV13 programme upon the S. pneumoniae population, including serotype replacement and antimicrobial resistance traits.

Differences in Pneumococcal and Haemophilus influenzae Natural Antibody Development in Papua New Guinean Children in the First Year of Life.

Background: Development of vaccines to prevent disease and death from Streptococcus pneumoniae, and nontypeable Haemophilus influenzae (NTHi), the main pathogens that cause otitis media, pneumonia, meningitis and sepsis, are a global priority. Children living in low and lower-middle income settings are at the highest risk of contracting and dying from these diseases. Improved vaccines with broader coverage are required. Data on the natural development of antibodies to putative vaccine antigens, especially in high-risk settings, can inform the rational selection of the best antigens for vaccine development. Methods: Serum IgG titres to four pneumococcal proteins (PspA1, PspA2, CbpA, and Ply) and five NTHi antigens (P4, P6, OMP26, rsPilA and ChimV4) were measured in sera collected from 101 Papua New Guinean children at 1, 4, 9, 10, 23 and 24 months of age using multiplexed bead-based immunoassays. Carriage density of S. pneumoniae and H. influenzae were assessed by quantitative PCR on genomic DNA extracted from nasopharyngeal swabs using species-specific primers and probes. All data were log-transformed for analysis using Student's unpaired t-tests with geometric mean titre (GMT) or density (GMD) calculated with 95% confidence intervals (CI). Results: Serum -pneumococcal protein-specific IgG titres followed a "U" shaped pattern, with a decrease in presumably maternally-derived IgG titres between 1 and 4 months of age and returning to similar levels as those measured at 1 month of age by 24 months of age. In contrast, NTHi protein-specific IgG titres steadily increased with age. There was no correlation between antibody titres and carriage density for either pathogen. Conclusion: This longitudinal study indicates that the waning of maternally- derived antibodies that is usually observed in infants, after infants does not occur for NTHi antigens in Papua New Guinean infants. Whether NTHi antigen IgG can be transferred maternally remains to be determined. Vaccines that are designed to specifically increase the presence of protective NTHi antibodies in the first few months of life may be most effective in reducing NTHi disease. Clinical Trial Registration: https://clinicaltrials.gov/, identifier NCT01619462.

PCV10 elicits Protein D IgG responses in Papua New Guinean children but has no impact on NTHi carriage in the first two years of life.

BACKGROUND: Nasopharyngeal colonisation with nontypeable Haemophilus influenzae (NTHi) is associated with development of infections including pneumonia and otitis media. The 10-valent pneumococcal conjugate vaccine (PCV10) uses NTHi Protein D (PD) as a carrier. Papua New Guinean children have exceptionally early and dense NTHi carriage, and high rates of NTHi-associated disease. Vaccination with PCV10 could potentially reduce NTHi carriage and disease in this population by inducing a NTHi PD immune response. METHODS: Serum and nasopharyngeal swabs were collected from 101 Papua New Guinean children at 1, 4, 9, 10, 23 and 24 months of age. Children received PCV10 (n = 55) or PCV13 (not containing NTHi PD) (n = 46) at 1, 2 and 3 months of age. NTHi carriage density was measured in swabs by qPCR. Serum PD-IgG levels were measured by bead-based immunoassay. RESULTS: Papua New Guinean children did naturally develop PD-IgG antibodies whose levels were increased at 4 months of age with PCV10 vaccination at 1-2-3 months. Despite this, most children were colonised with NTHi by 4 months of age (~95%) regardless of being vaccinated with PCV10 or PCV13, and PCV10 had no impact on NTHi carriage density. CONCLUSION: Early vaccination of infants with PCV10 elicited a robust PD antibody response but this had no impact on NTHi carriage. TRIAL REGISTRATION: ClinicalTrials.gov CTN NCT01619462.

Pneumococcal conjugate vaccine primes mucosal immune responses to pneumococcal polysaccharide vaccine booster in Papua New Guinean children.

INTRODUCTION: Invasive pneumococcal disease remains a major cause of hospitalization and death in Papua New Guinean (PNG) children. We assessed mucosal IgA and IgG responses in PNG infants vaccinated with pneumococcal conjugate vaccine (PCV) followed by a pneumococcal polysaccharide vaccine (PPV) booster. METHODS: Infants received 7-valent PCV (7vPCV) in a 0-1-2 (neonatal) or 1-2-3-month (infant) schedule, or no 7vPCV (control). At age 9 months all children received 23-valent PPV (23vPPV). IgA and IgG to 7vPCV and non-7vPCV (1, 5, 7F, 19A) serotypes were measured in saliva collected at ages 1, 2, 3, 4, 9, 10 and 18 months (131 children, 917 samples). Correlations were studied between salivary and serum IgG at 4, 10 and 18 months. RESULTS: Salivary IgA and IgG responses overall declined in the first 9 months. Compared to non-7vPCV recipients, salivary IgA remained higher in 7vPCV recipients for serotypes 4 at 3 months, 6B at 3 months (neonatal), and 14 at 3 (neonatal), 4 and 9 months (infant); and for salivary IgG for serotypes 4 at 3, 4 and 9 months, 6B at 9 months, 14 at 4 (neonatal) and 9 months, 18C at 3, 4, and 9 (infant) months, and 23F at 4 months. Following 23vPPV, salivary 7vPCV-specific IgA and IgG increased in 7vPCV-vaccinated children but not in controls; and salivary IgA against non-PCV serotypes 5 and 7F increased in 7vPCV recipients and non-recipients. Salivary and serum IgG against 7vPCV-serotypes correlated in 7vPCV-vaccinated children at 4 and 10 months of age. CONCLUSIONS: PCV may protect high-risk children against pneumococcal colonization and mucosal disease by inducing mucosal antibody responses and priming for mucosal immune memory that results in mucosal immune responses after booster PPV. Saliva can be a convenient alternative sample to serum to study PCV-induced systemic IgG responses.

Safety and Immunogenicity of Pneumococcal Conjugate Vaccines in a High-risk Population: A Randomized Controlled Trial of 10-Valent and 13-Valent Pneumococcal Conjugate Vaccine in Papua New Guinean Infants.

BACKGROUND: There are little data on the immunogenicity of PCV10 and PCV13 in the same high-risk population. METHODS: PCV10 and PCV13 were studied head-to-head in a randomized controlled trial in Papua New Guinea in which 262 infants received 3 doses of PCV10 or PCV13 at 1, 2, and 3 months of age. Serotype-specific immunoglobulin G (IgG) concentrations, and pneumococcal and nontypeable Haemophilus influenzae (NTHi) carriage were assessed prevaccination and at 4 and 9 months of age. Infants were followed up for safety until 9 months of age. RESULTS: One month after the third dose of PCV10 or PCV13, ˃80% of infants had IgG concentrations ≥0.35µg/mL for vaccine serotypes, and 6 months postvaccination IgG concentrations ≥0.35 µg/mL were maintained for 8/10 shared PCV serotypes in > 75% of children vaccinated with either PCV10 or PCV13. Children carried a total of 65 different pneumococcal serotypes (plus nonserotypeable). At 4 months of age, 92% (95% confidence interval [CI] 85-96) of children vaccinated with PCV10 and 81% (95% CI 72-88) vaccinated with PCV13 were pneumococcal carriers (P = .023), whereas no differences were seen at 9 months of age, or for NTHi carriage. Both vaccines were well tolerated and not associated with serious adverse events. CONCLUSIONS: Infant vaccination with 3 doses of PCV10 or PCV13 is safe and immunogenic in a highly endemic setting; however, to significantly reduce pneumococcal disease in these settings, PCVs with broader serotype coverage and potency to reduce pneumococcal carriage are needed. CLINICAL TRIALS REGISTRATION: NCT01619462.

Rationale and methods of a randomized controlled trial of immunogenicity, safety and impact on carriage of pneumococcal conjugate and polysaccharide vaccines in infants in Papua New Guinea.

BACKGROUND: Children in third-world settings including Papua New Guinea (PNG) experience early onset of carriage with a broad range of pneumococcal serotypes, resulting in a high incidence of severe pneumococcal disease and deaths in the first 2 years of life. Vaccination trials in high endemicity settings are needed to provide evidence and guidance on optimal strategies to protect children in these settings against pneumococcal infections. METHODS: This report describes the rationale, objectives, methods, study population, follow-up and specimen collection for a vaccination trial conducted in an endemic and logistically challenging setting in PNG. The trial aimed to determine whether currently available pneumococcal conjugate vaccines (PCV) are suitable for use under PNG's accelerated immunization schedule, and that a schedule including pneumococcal polysaccharide vaccine (PPV) in later infancy is safe and immunogenic in this high-risk population. RESULTS: This open randomized-controlled trial was conducted between November 2011 and March 2016, enrolling 262 children aged 1 month between November 2011 and April 2014. The participants were randomly allocated (1:1) to receive 10-valent PCV (10vPCV) or 13-valent PCV (13vPCV) in a 1-2-3-month schedule, with further randomization to receive PPV or no PPV at age 9 months, followed by a 1/5th PPV challenge at age 23 months. A total of 1229 blood samples were collected to measure humoral and cellular immune responses and 1238 nasopharyngeal swabs to assess upper respiratory tract colonization and carriage load. Serious adverse events were monitored throughout the study. Of the 262 children enrolled, 87% received 3 doses of PCV, 79% were randomized to receive PPV or no PPV at age 9 months, and 67% completed the study at 24 months of age with appropriate immunization and challenge. CONCLUSION: Laboratory testing of the many samples collected during this trial will determine the impact of the different vaccine schedules and formulations on nasopharyngeal carriage, antibody production and function, and immune memory. The final data will inform policy on pneumococcal vaccine schedules in countries with children at high risk of pneumococcal disease by providing direct comparison of an accelerated schedule of 10vPCV and 13vPCV and the potential advantages of PPV following PCV immunization. TRIAL REGISTRATION: ClinicalTrials.gov CTN NCT01619462, retrospectively registered on May 28, 2012.

Streptococcus pneumoniae and Haemophilus influenzae in paediatric meningitis patients at Goroka General Hospital, Papua New Guinea: serotype distribution and antimicrobial susceptibility in the pre-vaccine era.

BACKGROUND: Bacterial meningitis remains an important infection globally, with the greatest burden in children in low-income settings, including Papua New Guinea (PNG). We present serotype, antimicrobial susceptibility and outcome data from paediatric meningitis patients prior to introduction of Haemophilus influenzae type b (Hib) and pneumococcal conjugate vaccines (PCVs) in PNG, providing a baseline for evaluation of immunisation programs. METHODS: Cerebrospinal fluid (CSF) was collected from children admitted to Goroka General Hospital with suspected meningitis between 1996 and 2005. Culture and sensitivity was conducted, and pneumococci and H. influenzae were serotyped. Laboratory findings were linked to clinical outcomes. RESULTS: We enrolled 1884 children. A recognised pathogen was identified in 375 children (19.9%). Streptococcus pneumoniae (n = 180) and Hib (n = 153) accounted for 88.8% of pathogens isolated. 24 different pneumococcal serogroups were identified; non-PCV types 2, 24 and 46 accounted for 31.6% of pneumococcal meningitis. 10- and 13-valent PCVs would cover 44.1% and 45.4% of pneumococcal meningitis respectively. Pneumococcal isolates were commonly resistant to penicillin (21.5%) and 23% of Hib isolates were simultaneously resistant to ampicillin, co-trimoxazole and chloramphenicol. The case fatality rate in patients with a recognised bacterial pathogen was 13.4% compared to 8.5% in culture-negative patients. CONCLUSIONS: If implemented in routine expanded programme of immunisation (EPI) with high coverage, current PCVs could prevent almost half of pneumococcal meningitis cases. Given the diversity of circulating serotypes in PNG serotype replacement is of concern. Ongoing surveillance is imperative to monitor the impact of vaccines. In the longer term vaccines providing broader protection against pneumococcal meningitis will be needed.