Limited impact of neonatal or early infant schedules of 7-valent pneumococcal conjugate vaccination on nasopharyngeal carriage of Streptococcus pneumoniae in Papua New Guinean children: A randomized controlled trial

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).

A systematic review of pneumococcal conjugate vaccine impact on pneumococcal nasopharyngeal colonisation density in children under 5 years of age

BACKGROUND

High pneumococcal carriage density has been associated with severe pneumonia in some settings. The impact of pneumococcal conjugate vaccines (PCVs) on pneumococcal carriage density has been variable. The aim of this systematic literature review is to describe the effect of PCV7, PCV10 and PCV13 on pneumococcal colonisation density in children under five years old.

METHODS

We included peer reviewed English literature published between 2000 and 2021 to identify relevant articles using Embase, Medline and PubMed. Original research articles of any study design in countries where PCV has been introduced/studied were included. Quality (risk) assessment was performed using tools developed by the National Heart Brain and Lung Institute for inclusion in this review. We used a narrative synthesis to present results.

RESULTS

Ten studies were included from 1941 articles reviewed. There were two randomised controlled trials, two cluster randomised trials, one case control study, one retrospective cohort study and four cross sectional studies. Three studies used semiquantitative culture methods to determine density while the remaining studies used quantitative molecular techniques. Three studies reported an increase in density and three studies found a decrease in density among vaccinated compared with unvaccinated children. Four studies found no effect. There was considerable heterogeneity in the study populations, study design and laboratory methods.

CONCLUSION

There was no consensus regarding the impact of PCV on pneumococcal nasopharyngeal density. We recommend the use of standardised methods to evaluate PCV impact on density.

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.

Australia's Role in Pneumococcal and Human Papillomavirus Vaccine Evaluation in Asia-Pacific

Australian researchers have made substantial contributions to the field of vaccinology over many decades. Two examples of this contribution relate to pneumococcal vaccines and the human papillomavirus (HPV) vaccine, with a focus on improving access to these vaccines in low- and lower-middle-income countries (LLMICs). Many LLMICs considering introducing one or both of these vaccines into their National Immunisation Programs face significant barriers such as cost, logistics associated with vaccine delivery. These countries also often lack the resources and expertise to undertake the necessary studies to evaluate vaccine performance. This review summarizes the role of Australia in the development and/or evaluation of pneumococcal vaccines and the HPV vaccine, including the use of alternative vaccine strategies among countries situated in the Asia-Pacific region. The outcomes of these research programs have had significant global health impacts, highlighting the importance of these vaccines in preventing pneumococcal disease as well as HPV-associated diseases.

Lack of effectiveness of 13-valent pneumococcal conjugate vaccination against pneumococcal carriage density in Papua New Guinean infants

BACKGROUND

Papua New Guinea (PNG) introduced the 13-valent pneumococcal conjugate vaccine (PCV13) in 2014, with administration at 1, 2, and 3 months of age. PCV13 has reduced or eliminated carriage of vaccine types in populations with low pneumococcal carriage prevalence, carriage density and serotype diversity. This study investigated PCV13 impact on serotype-specific pneumococcal carriage prevalence, density, and serotype diversity in PNG infants, who have some of the highest reported rates of pneumococcal carriage and disease in the world.

METHODS

Nasopharyngeal swabs were collected at 1, 4 and 9 months of age from PCV13-vaccinated infants (n = 57) and age-/season-matched, unvaccinated infants (at approximately 1 month, n = 53; 4 months, n = 57; 9 months, n = 52). Serotype-specific pneumococcal carriage density and antimicrobial resistance genes were identified by qPCR and microarray.

RESULTS

Pneumococci were present in 89% of swabs, with 60 different serotypes and four non-encapsulated variants detected. Multiple serotype carriage was common (47% of swabs). Vaccine type carriage prevalence was similar between PCV13-vaccinated and unvaccinated infants at 4 and 9 months of age. The prevalence of non-vaccine type carriage was also similar between cohorts, with non-vaccine types present in three-quarters of samples (from both vaccinated and unvaccinated infants) by 4 months of age. The median pneumococcal carriage density was high and similar at each age group (~7.0 log₁₀genome equivalents/mL). PCV13 had no effect on overall pneumococcal carriage density, vaccine type density, non-vaccine type density, or the prevalence of antimicrobial resistance genes.

CONCLUSION

PNG infants experience dense and diverse pneumococcal colonisation with concurrent serotypes from 1 month of age. PCV13 had no impact on pneumococcal carriage density, even for vaccine serotypes. The low prevalence of vaccine serotypes, high pneumococcal carriage density and abundance of non-vaccine serotypes likely contribute to the lack of PCV13 impact on carriage in PNG infants. Indirect effects of the infant PCV programs are likely to be limited in PNG. Alternative vaccines with broader coverage should be considered.

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.

Nasopharyngeal carriage of otitis media pathogens in infants receiving 10-valent non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10), 13-valent pneumococcal conjugate vaccine (PCV13) or a mixed primary schedule of both vaccines: A randomised controlled trial

BACKGROUND

Aboriginal children in Northern Australia have a high burden of otitis media, driven by early and persistent nasopharyngeal carriage of otopathogens, including non-typeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae (Spn). In this context, does a combined mixed primary series of Synflorix and Prevenar13 provide better protection against nasopharyngeal carriage of NTHi and Spn serotypes 3, 6A and 19A than either vaccine alone?

METHODS

Aboriginal infants (n = 425) were randomised to receive Synflorix™ (S, PHiD-CV10) or Prevenar13™ (P, PCV13) at 2, 4 and 6 months (_SSS or _PPP, respectively), or a 4-dose early mixed primary series of PHiD-CV10 at 1, 2 and 4 months and PCV13 at 6 months of age (SSSP). Nasopharyngeal swabs were collected at 1, 2, 4, 6 and 7 months of age. Swabs of ear discharge were collected from tympanic membrane perforations.

FINDINGS

At the primary endpoint at 7 months of age, the proportion of nasopharyngeal (Np) swabs positive for PCV13-only serotypes 3, 6A, or 19A was 0%, 0.8%, and 1.5% in the _PPP, _SSS, and SSSP groups respectively, and NTHi 55%, 52%, and 52% respectively, and no statistically significant vaccine group differences in other otopathogens at any age. The most common serotypes (in order) were 16F, 11A, 10A, 7B, 15A, 6C, 35B, 23B, 13, and 15B, accounting for 65% of carriage. Ear discharge swabs (n = 108) were culture positive for NTHi (52%), S. aureus (32%), and pneumococcus (20%).

CONCLUSIONS

Aboriginal infants experience nasopharyngeal colonisation and tympanic membrane perforations associated with NTHi, non-PCV13 pneumococcal serotypes and S. aureus in the first months of life. Nasopharyngeal carriage of pneumococcus or NTHi was not significantly reduced in the early 4-dose combined SSSP group compared to standard _PPP or _SSS schedules at any time point. Current pneumococcal conjugate vaccine formulations do not offer protection from early onset NTHi and pneumococcal colonisation in this high-risk population.

An observational study of the reactogenicity and immunogenicity of 13-valent pneumococcal conjugate vaccine in women of childbearing age in Papua New Guinea

Background

Maternal immunization with pneumococcal conjugate vaccine (PCV) may protect young infants in high-risk settings against the high risk of pneumococcal infections in early life. The aim of this study was to determine the safety and immunogenicity of 13-valent PCV (PCV13) in healthy women of childbearing age in PNG.

Methods

As part of this observational study, 50 non-pregnant women of childbearing age (18-45 yrs. old) living in the highlands of PNG were vaccinated with a single dose of PCV13. Local and systemic reactogenicity were assessed 24–48 h after vaccination. Venous blood samples were collected before and 1 month after vaccination to measure PCV13 serotype-specific IgG antibody concentrations.

Results

No severe adverse effects were reported during the 1-month follow-up period. IgG antibody concentrations significantly increased after vaccination for all PCV13 serotypes. One month after vaccination IgG antibody levels ≥2.5 μg/mL were reached in at least 75% of women for all PCV13 serotypes, except serotype 3, and ≥ 5 μg/mL in at least 75% of women for 7 serotypes (serotypes 6B, 9 V, 14, 18C, 19A, 19F and 23F).

Conclusion

PCV13 is safe and immunogenic in women of childbearing age living in a high-risk setting in PNG. This supports the implementation of studies to investigate the safety and immunogenicity of maternal PCV vaccination in high-risk settings as a strategy to protect infants in these settings against the high risk of pneumococcal infections in early life.

Trial registration

NCT04183322. Registered 3 December 2019 - Retrospectively registered

Supplementary information

Supplementary information accompanies this paper at 10.1186/s41479-020-00076-1.

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.

Panel 6: Otitis media and associated hearing loss among disadvantaged populations and low to middle-income countries

OBJECTIVE:

Summarise the published evidence on otitis media and associated hearing loss in low to middle-income countries (LMIC) and disadvantaged populations.

DATA SOURCES:

PubMed and other databases.

REVIEW METHODS:

Firstly, sensitive search strategy using ‘otitis media’, combined with specific key words for each topic of the review, from January 2015 to June 2019. Then, restriction to LMIC and disadvantaged populations. Topics covered included prevention, epidemiology, risk factors, microbiology, prognosis, diagnosis, and treatment.

CONCLUSIONS:

There was a high degree of methodological heterogeneity and high risk of bias. The majority of studies were school-based. In Africa, Asia and Oceania (e.g., Australian Aboriginal populations) the prevalence of OM was respectively 8% (range 3–16%), 14% (range 7–22%) and 50% (4–95%). Prevalence of any hearing loss in these regions was 12% (range 8–17%), 12% (range 3–24%), and 26% (range 25–28%) respectively. Risk factors in LMIC and disadvantaged populations included age, gender, exposure to smoke and pollution. Microbiology was reported for otitis media with effusion at time of surgery or ear discharge (acute otitis media with perforation or chronic suppurative otitis media). Specimen handling and processing in hospital laboratories was associated with low detection of S. pneumoniae and H. influenzae. Case series described complicated cases of OM due to M. tuberculosis, multidrug resistance and HIV. QOL studies identified discrimination of persons with OM and hearing loss. Diagnostic methods varied greatly, from naked eye to tympanometry. Treatment interventions were reported from four RCTs. Non-RCTs included evaluations of guidelines, surgery outcomes, access to ENTs.

IMPLICATIONS FOR CLINICAL PRACTICE:

Chronic suppurative otitis media, otitis media with effusion and conductive hearing loss are common in LMIC and disadvantaged populations. Paucity of research, poor regional representation, non-standardised methods and low-quality reporting preclude accurate assessment of disease burden in LMIC and disadvantaged populations. Awareness and adherence to reporting Guidelines should be promoted.

A Comparison of Pneumococcal Nasopharyngeal Carriage in Very Young Fijian Infants Born by Vaginal or Cesarean Delivery

IMPORTANCE

Pneumococcal nasopharyngeal carriage is a prerequisite for pneumococcal disease. The main transmission route is from toddlers, who commonly carry pneumococci. However, neonatal pneumococcal disease case reports suggest that vertical pneumococcal transmission may also occur.

OBJECTIVE

To describe and compare pneumococcal nasopharyngeal carriage and density by infant mode of delivery in young Fijian infants.

DESIGN, SETTING, AND PARTICIPANTS

Annual cross-sectional surveys were performed in Suva, Fiji, before the introduction of 10-valent pneumococcal conjugate vaccine (PCV10), from September 14 to December 20, 2012, and after PCV10 was introduced, from July 11 to November 19, 2013; July 15 to December 9, 2014; and August 13 to November 19, 2015. Caregivers of 2006 infants aged 5 to 8 weeks participated in the surveys. Statistical analysis was performed from May 24, 2018, to August 12, 2019.

EXPOSURES

Caregivers provided data on infant mode of delivery and demographics via interviewer-led survey.

MAIN OUTCOMES AND MEASURES

Pneumococci in swab samples were detected and quantified by lytA quantitative polymerase chain reaction with molecular serotyping by microarray. Pneumococci were categorized as PCV10 or non-PCV10 serotypes.

RESULTS

Of the 2006 infants (976 girls and 1030 boys; mean [SD] age, 6.1 [0.02] weeks]), 1742 (86.8%) were born vaginally and 264 were born by cesarean delivery. Infants delivered vaginally, compared with those born by cesarean delivery, had a higher prevalence of overall pneumococcal nasopharyngeal carriage (470 of 1722 [27.3%; 95% CI, 25.2%-29.4%] vs 47 of 260 [18.1%; 95% CI, 13.6%-23.3%]; P = .002), PCV10 carriage (113 of 1698 [6.7%; 95% CI, 5.5%-7.9%] vs 8 of 256 [3.1%; 95% CI, 1.4%-6.1%]; P = .03), and non-PCV10 carriage (355 of 1698 [20.9%; 95% CI, 19.0%-22.9%] vs 38 of 256 [14.8%; 95% CI, 10.7%-19.8%]; P = .02), and had higher median densities of overall pneumococci (4.9 log10 genome equivalents [GE]/mL [interquartile range, 4.8-5.0 log10 GE/mL] vs 4.5 log10 GE/mL [interquartile range, 4.1-4.6 log10 GE/mL]; P = .01) and non-PCV10 pneumococci (4.9 log10 GE/mL [interquartile range, 4.7-5.0 log10 GE/mL] vs 4.4 log10 GE/mL [interquartile range, 4.0-4.7 log10 GE/mL]; P = .01). Vaginal delivery was associated with overall (adjusted odds ratio, 1.57 [95% CI, 1.10-2.23]; P = .01) and non-PCV10 (adjusted odds ratio, 1.49 [95% CI, 1.01-2.20]; P = .04]) pneumococcal nasopharyngeal carriage. Vaginal delivery was not associated with PCV10 carriage (adjusted odds ratio, 1.67 [95% CI, 0.80-3.51]; P = .17). After adjustment, vaginal delivery was not associated with density.

CONCLUSIONS AND RELEVANCE

Pneumococcal nasopharyngeal carriage prevalence and density were higher in infants delivered vaginally compared with those delivered by cesarean birth. After adjustment, vaginal delivery was associated with pneumococcal carriage. Differences in carriage by mode of delivery may be due to differential exposure to the vaginal microbiota during delivery and the effect of intrapartum antibiotics during cesarean delivery on the infant microbiome. Our findings also raise the hypothesis that vertical transmission may contribute to pneumococcal acquisition.

Immunogenicity and Immune Memory after a Pneumococcal Polysaccharide Vaccine Booster in a High-Risk Population Primed with 10-Valent or 13-Valent Pneumococcal Conjugate Vaccine: A Randomized Controlled Trial in Papua New Guinean Children

We investigated the immunogenicity, seroprotection rates and persistence of immune memory in young children at high risk of pneumococcal disease in Papua New Guinea (PNG). Children were primed with 10-valent (PCV10) or 13-valent pneumococcal conjugate vaccines (PCV13) at 1, 2 and 3 months of age and randomized at 9 months to receive PPV (PCV10/PPV-vaccinated, n = 51; PCV13/PPV-vaccinated, n = 52) or no PPV (PCV10/PPV-naive, n = 57; PCV13/PPV-naive, n = 48). All children received a micro-dose of PPV at 23 months of age to study the capacity to respond to a pneumococcal challenge. PPV vaccination resulted in significantly increased IgG responses (1.4 to 10.5-fold change) at 10 months of age for all PPV-serotypes tested. Both PPV-vaccinated and PPV-naive children responded to the 23-month challenge and post-challenge seroprotection rates (IgG ≥ 0.35 μg/mL) were similar in the two groups (80⁻100% for 12 of 14 tested vaccine serotypes). These findings show that PPV is immunogenic in 9-month-old children at high risk of pneumococcal infections and does not affect the capacity to produce protective immune responses. Priming with currently available PCVs followed by a PPV booster in later infancy could offer improved protection to young children at high risk of severe pneumococcal infections caused by a broad range of serotypes.

First International Precision Vaccines Conference: Multidisciplinary Approaches to Next-Generation Vaccines

Vaccines represent a remarkable success in the history of medicine since they have prevented and, in some instances, eradicated a range of infectious diseases. However, for many existing vaccines, immunogenicity is limited, requiring multiple booster doses, and we are still unable to target many pathogens due to intrinsic features of the microorganism, such as genetic/antigenic variability between strains, and our limited understanding of the variables that regulate vaccine responsiveness, including age- and sex-specific differences. Moreover, the traditional approach to vaccine development is often empirical, relying on inactivation of microorganisms or purification of their components, which are usually less immunogenic than the whole microorganism from which they derive. This approach has yielded multiple important vaccines but has failed to consistently generate vaccines that are sufficiently immunogenic in populations with limited immune responsiveness such as newborns and elderly individuals. In an effort to trigger impactful collaborations, a community of scientists gathered in Boston in the United States for the first biennial International Precision Vaccines Conference, sponsored by the Boston Children's Hospital Precision Vaccines Program, to discuss innovation in vaccinology. Recent advancements in the field of systems biology that can identify vaccine immunogenicity biomarkers for target populations, in human in vitro models, and in novel adjuvant and formulation strategies offer unprecedented opportunities to dissect the human immune response to vaccines and inform dramatic improvements in vaccine efficacy. These approaches are poised to have a major scientific and translational impact in vaccinology.

Determining the pneumococcal conjugate vaccine coverage required for indirect protection against vaccine-type pneumococcal carriage in low and middle-income countries: a protocol for a prospective observational study

INTRODUCTION

Pneumococcal conjugate vaccines (PCVs) prevent disease through both direct protection of vaccinated individuals and indirect protection of unvaccinated individuals by reducing nasopharyngeal (NP) carriage and transmission of vaccine-type (VT) pneumococci. While the indirect effects of PCV vaccination are well described, the PCV coverage required to achieve the indirect effects is unknown. We will investigate the relationship between PCV coverage and VT carriage among undervaccinated children using hospital-based NP pneumococcal carriage surveillance at three sites in Asia and the Pacific.

METHODS AND ANALYSIS

We are recruiting cases, defined as children aged 2-59 months admitted to participating hospitals with acute respiratory infection in Lao People's Democratic Republic, Mongolia and Papua New Guinea. Thirteen-valent PCV status is obtained from written records. NP swabs are collected according to standard methods, screened using lytA qPCR and serotyped by microarray. Village-level vaccination coverage, for the resident communities of the recruited cases, is determined using administrative data or community survey. Our analysis will investigate the relationship between VT carriage among undervaccinated cases (indirect effects) and vaccine coverage using generalised estimating equations.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the relevant ethics committees at participating sites. The results are intended for publication in open-access peer-reviewed journals and will demonstrate methods suitable for low- and middle-income countries to monitor vaccine impact and inform vaccine policy makers about the PCV coverage required to achieve indirect protection.

Neonatal Immunization: Rationale, Current State, and Future Prospects

Infections take their greatest toll in early life necessitating robust approaches to protect the very young. Here, we review the rationale, current state, and future research directions for one such approach: neonatal immunization. Challenges to neonatal immunization include natural concern about safety as well as a distinct neonatal immune system that is generally polarized against Th1 responses to many stimuli such that some vaccines that are effective in adults are not in newborns. Nevertheless, neonatal immunization could result in high-population penetration as birth is a reliable point of healthcare contact, and offers an opportunity for early protection of the young, including preterm newborns who are deficient in maternal antibodies. Despite distinct immunity and reduced responses to some vaccines, several vaccines have proven safe and effective at birth. While some vaccines such as polysaccharide vaccines have little effectiveness at birth, hepatitis B vaccine can prime at birth and requires multiple doses to achieve protection, whereas the live-attenuated Bacille Calmette-Guérin (BCG), may offer single shot protection, potentially in part via heterologous ("non-specific") beneficial effects. Additional vaccines have been studied at birth including those directed against pertussis, pneumococcus, Haemophilus influenza type B and rotavirus providing important lessons. Current areas of research in neonatal vaccinology include characterization of early life immune ontogeny, heterogeneity in and heterologous effects of BCG vaccine formulations, applying systems biology and systems serology, in vitro platforms that model age-specific human immunity and discovery and development of novel age-specific adjuvantation systems. These approaches may inform, de-risk, and accelerate development of novel vaccines for use in early life. Key stakeholders, including the general public, should be engaged in assessing the opportunities and challenges inherent to neonatal immunization.

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.

Pneumococcal responses are similar in Papua New Guinean children aged 3-5 years vaccinated in infancy with pneumococcal polysaccharide vaccine with or without prior pneumococcal conjugate vaccine, or without pneumococcal vaccination

Trial design

In an earlier trial, Papua New Guinean (PNG) children at high risk of pneumococcal disease were randomized to receive 0 or 3 doses of 7-valent pneumococcal conjugate vaccine (PCV7), followed by a single dose of 23-valent pneumococcal polysaccharide vaccine (PPV23) at 9 months of age. We here studied in a non-randomized follow-up trial the persistence of pneumococcal immunity in these children at 3–5 years of age (n = 132), and in 121 community controls of a similar age with no prior pneumococcal vaccination.

Methods

Circulating IgG antibody titers to all PCV7 and PPV23-only serotypes 2, 5 and 7F were measured before and after challenge with 1/5^th of a normal PPV23 dose. Serotype-specific memory B-cells were enumerated at 10 months and 3–5 years of age for a subgroup of study children.

Results

Serotype-specific IgG antibody titers before and after challenge were similar for children who received PCV7/PPV23, PPV23 only, or no pneumococcal vaccines. Before challenge, at least 89% and 59% of children in all groups had serotype-specific titers ≥ 0.35μg/ml and ≥ 1.0 μg/ml, respectively. Post-challenge antibody titers were higher or similar to pre-challenge titers for most children independent of pneumococcal vaccination history. The rise in antibody titers was significantly lower when pre-challenge titers were higher. Overall the relative number of serotype-specific memory B-cells remained the same or increased between 10 months and 3–5 years of age, and there were no differences in serotype-specific memory B-cell numbers at 3–5 years of age between the three groups.

Conclusions

Immunity induced by PCV7 and/or PPV23 immunization in infancy does not exceed that of naturally acquired immunity in 3-5-year-old children living in a highly endemic area. Also, there was no evidence that PPV23 immunization in the first year of life following PCV7 priming induces longer-term hypo-responsiveness.

Trial registration

Clinicaltrials.gov NCT01414504 and NCT00219401.

Cord blood Streptococcus pneumoniae-specific cellular immune responses predict early pneumococcal carriage in high-risk infants in Papua New Guinea

In areas where Streptococcus pneumoniae is highly endemic, infants experience very early pneumococcal colonization of the upper respiratory tract, with carriage often persisting into adulthood. We aimed to explore whether newborns in high‐risk areas have pre‐existing pneumococcal‐specific cellular immune responses that may affect early pneumococcal acquisition. Cord blood mononuclear cells (CBMC) of 84 Papua New Guinean (PNG; high endemic) and 33 Australian (AUS; low endemic) newborns were stimulated in vitro with detoxified pneumolysin (dPly) or pneumococcal surface protein A (PspA; families 1 and 2) and compared for cytokine responses. Within the PNG cohort, associations between CBMC dPly and PspA‐induced responses and pneumococcal colonization within the first month of life were studied. Significantly higher PspA‐specific interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α, interleukin (IL)‐5, IL‐6, IL‐10 and IL‐13 responses, and lower dPly‐IL‐6 responses were produced in CBMC cultures of PNG compared to AUS newborns. Higher CBMC PspA‐IL‐5 and PspA‐IL‐13 responses correlated with a higher proportion of cord CD4 T cells, and higher dPly‐IL‐6 responses with a higher frequency of cord antigen‐presenting cells. In the PNG cohort, higher PspA‐specific IL‐5 and IL‐6 CBMC responses were associated independently and significantly with increased risk of earlier pneumococcal colonization, while a significant protective effect was found for higher PspA‐IL‐10 CBMC responses. Pneumococcus‐specific cellular immune responses differ between children born in pneumococcal high versus low endemic settings, which may contribute to the higher risk of infants in high endemic settings for early pneumococcal colonization, and hence disease.