Nationwide population-based surveillance of invasive pneumococcal disease in Japanese children: Effects of the seven-valent pneumococcal conjugate vaccine

Pediatric otitis media in Japan: A nationwide longitudinal study of the pre- and post-pneumococcal conjugate vaccine eras born in 2001 and 2010

BACKGROUND

Otitis media (OM) is a prevalent respiratory disease in children and poses significant public health challenges due to its impact on child health and economic burdens. However, there have no nationwide epidemiological studies conducted in Japan. This study investigates the epidemiological trends of OM in Japan, taking into account the impact of the 7-valent pneumococcal conjugate vaccine (PCV7) introduction.

METHOD

This study was retrospective cohort study using secondary data on the nationwide longitudinal birth cohort. This survey followed two cohorts born in 2001 (pre-PCV era) and 2010 (post-PCV era) until the age of 9. Every year, parents were surveyed about their children's health status, including occurrences of OM. The annual period prevalence and cumulative incidence of OM were assessed in this study, and the two cohorts were compared using a modified Poisson regression model adjusted environmental factors with the 2001 cohort as reference.

RESULT

The study included 47,015 children from the 2001 cohort and 38,554 from the 2010 cohort. Peak annual period prevalence of OM varied by era. Cumulative incidence was 13.8 % for the 2001 cohort and 18.5 % for the 2010 cohort by 1.5 years of age and 28.9 % and 33.3 %, respectively, by 3.5 years of age. In particular, from the fourth survey onward, covering ages 2.5-3.5 years, a shift was observed from an increased risk to a decreased risk of OM.

CONCLUSION

This nationwide longitudinal study emphasizes variations in OM epidemiology across Japan over time, with changes potentially influenced by the introduction of PCV7. In this study, due to the absence of individual PCV7 vaccination data, the effect of PCV7 was estimated based on the vaccination rate at the population level. The results suggest a notable decrease in the incidence of OM in later years, aligning with the increased uptake of PCV7.

Disease burden of main bacterial infections in Japan, 2015-2020: A population-level study

INTRODUCTION

Comprehensive evidence about the burden of infectious diseases in the Western Pacific Region is scarce. We thus examined the disease burden of infectious diseases in Japan in terms of disability-adjusted life years (DALYs).

METHODS

We extracted national claims data from Japan's universal health insurance system to estimate the burden of disease for selected infections between 2015 and 2020 using DALYs. The mortality rate, disability duration and severity weight of each disease were estimated based on national data and literature reviews.

RESULTS

Disease burden per 100,000 population was 1307.0 in 2015 and 972.1 in 2020 for bloodstream infections (BSI), 796.5 DALYs in 2015 and 498.9 DALYs in 2020 for pneumonia, 171.5 in 2015 and 149.4 in 2020 for meningitis and 11.6 in 2015 and 11.4 in 2020 for urinary tract infections (UTI). Only surgical site infections (SSI) showed a slightly increasing trend over the 5-year period, from 2.2 in 2015 to 2.8 in 2020.

CONCLUSIONS

Our results showed that the disease burden of the five major infectious diseases was higher in Japan than in other countries. However, while the burden of SSI increased, the burden of pneumonia, meningitis, BSI and UTI gradually decreased year on year. The possible causes of the decreased morbidity should be examined in future work.

Safety and immunogenicity of a 15-valent pneumococcal conjugate vaccine in Japanese healthy infants: A Phase I study (V114-028)

This Phase I study evaluated the safety, tolerability, and immunogenicity of V114, a 15-valent pneumococcal conjugate vaccine (PCV), via subcutaneous (SC) or intramuscular (IM) administration, in healthy Japanese infants 3 months of age. A total of 133 participants were randomized to receive four doses (3 + 1 regimen) of V114-SC (n = 44), V114-IM (n = 45), or 13-valent PCV (PCV13)-SC (n = 44) at 3, 4, 5, and 12-15 months of age. Diphtheria, tetanus, and pertussis-inactivated poliovirus (DTaP-IPV) vaccine was administered concomitantly at all vaccination visits. The primary objective was to assess the safety and tolerability of V114-SC and V114-IM. Secondary objectives were to assess the immunogenicity of PCV and DTaP-IPV at 1-month post-dose 3 (PD3). On days 1-14 following each vaccination, the proportions of participants with systemic adverse events (AEs) were comparable across interventions, whereas injection-site AEs were higher with V114-SC (100.0%) and PCV13-SC (100.0%) than with V114-IM (88.9%). Most AEs were mild or moderate in severity and no vaccine-related serious AEs or deaths were reported. Serotype-specific immunoglobulin G (IgG) response rates at 1-month PD3 were comparable across groups for most shared serotypes between V114 and PCV13. For additional V114 serotypes 22F and 33F, IgG response rates were higher with V114-SC and V114-IM than with PCV13-SC. DTaP-IPV antibody response rates at 1-month PD3 for V114-SC and V114-IM were comparable with PCV13-SC. Findings suggest that vaccination with V114-SC or V114-IM in healthy Japanese infants is generally well tolerated and immunogenic.

Safety and immunogenicity of 15-valent pneumococcal conjugate vaccine in Japanese healthy infants: A phase III study (V114-033)

BACKGROUND

This phase III study evaluated safety, tolerability, and immunogenicity of V114 (15-valent pneumococcal conjugate vaccine) in Japanese infants. V114 contains all 13 serotypes in PCV13 plus additional serotypes 22F and 33F.

METHODS

Healthy Japanese infants were randomized to receive three primary doses of V114 or PCV13 (dose 1 at 2-6 months of age; doses 2 and 3 ≥ 27 days after prior dose), plus a toddler dose at 12-15 months of age. Adverse events (AEs) were collected on Days 1-14 following each vaccination. Serotype-specific anti-pneumococcal immunoglobulin G (IgG) was measured 30 days post-dose 3, pre-dose 4, and 30 days post-dose 4. Primary objectives included non-inferiority of V114 to PCV13 for the 13 shared serotypes based on serotype-specific IgG response rates (IgG ≥ 0.35 μg/mL) and geometric mean concentration (GMC) ratios, and for serotypes 22F and 33F based on IgG response rates and compared with the lowest response of any serotype in the PCV13 group, at 30 days post-dose 3.

RESULTS

Overall, 694 infants were randomized to V114 (n = 347) or PCV13 (n = 347). Proportions of participants with solicited and serious AEs were comparable between vaccination groups. V114 met non-inferiority criteria for all 13shared serotypes, based on difference in proportion of responders (lower bound of two-sided 95 % confidence interval [CI] > -10.0) and IgG GMC ratios (V114/PCV13, lower bound of two-sided 95 % CI > 0.5) at 30 days post-dose 3. The non-inferiority criterion based on IgG response rates was met for serotype 22F, but narrowly missed for serotype 33F (90.9 %, lower bound of two-sided 95 % CI -10.6).

CONCLUSION

In Japanese infants, a four-dose series of V114 was generally well tolerated. Compared with PCV13, V114 provided non-inferior immune responses to the 13 shared serotypes and higher immune responses to serotype 22F and 33F post-primary series.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04384107; EudraCT 2019-003644-68.

Serotypes and Antibiotic Resistance of Streptococcus pneumoniae before and after the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine for Adults and Children in a Rural Area in Japan

The increase in non-vaccine serotypes of Streptococcus pneumoniae and their multidrug resistance have become an issue following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13). In this study, we investigated the serotypes and drug resistance of S. pneumoniae detected in adult and pediatric outpatients at a hospital in a rural area of Japan between April 2012 and December 2016. Serotypes of the bacterium were identified using the capsular swelling test and multiplex polymerase chain reaction testing of DNA extracted from the specimens. Antimicrobial susceptibility was determined using the broth microdilution method. The serotype 15A was classified using multilocus sequence typing. The results showed that the prevalence of non-vaccine serotypes increased significantly in children from 50.0% in 2012-2013 to 74.1% in 2016 (p ≤ 0.006) and in adults from 15.8% in 2012-2013 to 61.5% in 2016 (p ≤ 0.026), but no increase in drug-resistant isolates was evident. However, an increase in the drug-resistant serotypes 15A and 35B was observed in children. Although isolates of these two serotypes showed cefotaxime susceptibility, cefotaxime resistance was confirmed for the serotype 15A isolates. Future trends in the spread of these isolates should be monitored with caution.

Cost-effectiveness analysis of pediatric immunization program with 15-valent pneumococcal conjugate vaccine in Japan

BACKGROUND

The 15-valent pneumococcal conjugate vaccine (PCV15 or V114) has recently been approved for pediatric vaccination against pneumococcal diseases (PDs) in Japan. The study aims to evaluate the cost-effectiveness of pediatric vaccination with V114 versus 13-valent PCV (PCV13) in Japan.

METHODS

The study used a decision analytical Markov model to estimate the cost and effectiveness outcomes for a birth cohort in Japan over a 10-year time horizon. The model tracked the occurrences of acute PD events, including invasive PD (IPD), non-bacteremic pneumococcal pneumonia (NBPP) and pneumococcal acute otitis media (AOM) and the long-term impact of post-meningitis sequalae. Vaccine effectiveness was estimated based on literature and assumptions, and accounted for indirect effects and vaccine waning. The base case took the societal perspective, including both direct and indirect costs, while a healthcare payer perspective was modeled in a scenario analysis. Additional scenario analyses and sensitivity analyses were conducted.

RESULTS

In the base case, V114 was associated with an incremental gain of 24 quality-adjusted life years and a reduction of ¥365,610,955 in total costs compared to PCV13. It was expected to reduce the number of pneumococcal AOM, NBPP, and IPD cases by 1,832, 1,333 and 25, respectively. All scenario analyses and most sensitivity analyses showed that V114 was a dominant strategy compared to PCV13.

CONCLUSIONS

Pediatric vaccination with V114 is expected to lead to cost savings and more health benefits compared to PCV13 in Japan from both societal and healthcare payer perspectives. The findings are robust under plausible assumptions and inputs.

Epidemiology and bacterial characteristics of invasive group B streptococcus disease: a population-based study in Japan in 2010-2020

This is the first report on a population-based prospective study of invasive group B streptococcus (GBS) disease among children aged <15 years conducted over a period of 11 years in Japan. This study investigated the incidence and clinical manifestations of invasive GBS disease in children in Chiba Prefecture, Japan, and analysed the serotypes and drug susceptibility of GBS strains isolated during the study period. Overall, 127 episodes of invasive GBS disease were reported in 123 patients. Of these, 124 were observed in 120 patients aged <1 year, and the remaining three episodes were reported in a 9-year-old child and two 14-year-old children with underlying disease. For patients aged <1 year, the incidence rate per 1000 live births was 0.24 (0.15-0.36). The incidences of early-onset disease and late-onset disease were 0.04 (0.0-0.09) and 0.17 (0.08-0.25), respectively. The rate of meningitis was 45.2%, and the incidence of GBS meningitis was higher than that of other invasive diseases among children in Japan. Of the 109 patients for whom prognosis was available, 7 (6.4%) died and 21 (19.3%) had sequelae. In total, 68 strains were analysed. The most common were serotype III strains (n = 42, 61.8%), especially serotype III/ST17 strains (n = 22, 32.4%). This study showed that the incidence of invasive GBS disease among Japanese children was constant during the study period. Because of the high incidence of meningitis and disease burden, new preventive strategies, such as GBS vaccine, are essential.

Long-term impact of pneumococcal conjugate vaccines for children on adult pneumococcal pneumonia in Japan: Two multicenter observational studies from 2011 to 2020

BACKGROUND

Pediatric pneumococcal conjugate vaccines (PCVs) introduction has directly and indirectly reduced pneumococcal pneumonia and invasive disease caused by PCV-covered serotypes among children and adults globally. In Japan, both PCV7 and PCV13 were introduced into the national immunization program (NIP) for children in 2013. However, the long-term impact of PCV use in children on adult pneumococcal pneumonia in Japan remains unclear.

METHODS

We assessed serotypes isolated from adult pneumococcal pneumonia patients (in- and outpatients) in two multicenter observational studies in Japan: 2011-2014 and 2016-2020. The latter study period was divided into two periods to evaluate changes after PCV introduction in children. The Quellung reaction was used to determine serotypes. We evaluated trends of individual and vaccine-covered serotypes over three periods and assessed the difference in changes by patient group before and after the introduction of pediatric PCVs.

RESULTS

A total of 650 patients were enrolled: 224, 322, and 104 in 2011-2014, 2016-2017, and 2018-2020, respectively. The median age was 73 years; 59.7% (388/650) were male; 86.9% (565/650) had comorbidities; and 10.2% (66/650) were nursing-home residents. The proportion of PCV13 serotypes decreased from 52.7% in 2011-2014 to 30.4% in 2016-2017 (p <0.001) after PCV13 introduction for children. However, PCV13, PCV15, and PCV20 serotypes still accounted for 38.5, 43.3, and 59.6% of total pneumococcal pneumonia in 2018-2020, respectively. Decline of PCV13 serotypes was more marked in patients aged ≥65 (-23.5%; p <0.001) than those aged <65 (-12.3%; p = 0.104) from 2011-2014 to 2016-2020. The proportion of PPSV23 non-PCV13 serotypes didn't change over time.

CONCLUSIONS

The proportion of adult pneumococcal pneumonia caused by PCV13 serotypes in Japan declined after pediatric PCVs introduction into NIP, possibly due to indirect effects of pediatric PCVs. However, use of new PCVs in Japanese adults may potentially prevent additional pneumococcal pneumonia cases. Now, pneumococcal vaccination strategy for older adults requires discussion.

Dynamic changes in clinical characteristics and serotype distribution of invasive pneumococcal disease among adults in Japan after introduction of the pediatric 13-valent pneumococcal conjugate vaccine in 2013-2019

Nationwide population-based surveillance for invasive pneumococcal disease (IPD) is being conducted in few Asian countries. We aimed to evaluate the clinical characteristics and serotype distribution among Japanese adult patients with IPD after introduction of the pediatric 13-valent pneumococcal conjugate vaccine (PCV13) in 2013. IPD surveillance was conducted among adults between 2013 and 2019, and 1,995 patients were analyzed by time period (early, 2013-2015; middle, 2016-2017; late, 2018-2019). We found that the period of 2018-2019 was independently associated with a lower risk of fatal outcome, compared with the period of 2013-2015. The proportion of those with serotype PCV13-nonPCV7 decreased significantly in patients aged 15-64 years and in those aged ≥ 65 years within 3 years after the introduction of pediatric PCV13. By contrast, the proportion of those with nonvaccine serotype increased significantly in those aged ≥ 65 years, but not in those aged 15-64 years. No significant change was found in the proportion of 23-valent polysaccharide pneumococcal vaccine (PPSV23)-nonPCV13 in both of adults aged 15-64 years and ≥ 65 years. The proportions of PCV15-, PCV20- and PCV24-covered serotypes were 38%, 56% and 58% in adult patients with IPD aged ≥ 65 years during the late period. Our data on the serotype distribution support an indirect effect from pediatric PCV13 use among adults, and afford a basis for estimates of protection against IPD by vaccination with newly developed PCVs in older adults in Japan.

Epidemiological characteristics in serotype 24 pediatric invasive pneumococcal disease according to an 11-year population-based study in Japan

After the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), serotype replacement has occurred in Japan, and serotype 24 has become the most common serotype in paediatric invasive pneumococcal disease (IPD). To understand the characteristics of serotype 24-IPD in Japanese children in the post-PCV13 era, we conducted a retrospective study in children aged ≤15 years from 2010 to 2020 using a database of paediatric IPD surveillance in Chiba prefecture, Japan. We identified a total of 357 IPD cases and collected clinical information on 225 cases (24: 32 cases, non-24: 193 cases). Compared with the non-serotype 24-IPD, serotype 24-IPD was independently related to be <2 years of age [odds ratio (OR) 3.91, 95% confidence interval (CI) 1.47–10.44; P = 0.0064] and bacteremia (OR 2.28, 95% CI 1.01–5.13; P = 0.0475), as a result of the multivariate regression analysis. We also conducted a bacterial analysis, and the isolates of serotype 24-IPD had tendencies of PCG-susceptible (24: 100.0%, non-24: 61.3%; P < 0.0001) and macrolide-resistance (24: 100.0%, non-24: 87.3%; P = 0.0490). Their multilocus sequence typing was mostly ST2572 and the variants, which were unique to Japan. This tendency might have been a result of the progress made in the Japanese PCV13 immunisation programme.

Pneumococcal meningitis in adults in 2014-2018 after introduction of pediatric 13-valent pneumococcal conjugate vaccine in Japan

We assessed the impact of the pediatric 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal meningitis in adults in Japan in 2014–2018 by comparing epidemiological characteristics of adults with invasive pneumococcal disease with (n = 222) and without (n = 1258) meningitis. The annual incidence of pneumococcal meningitis in 2016–2018 was 0.20–0.26 cases/100,000 population. Age (p < 0.001) and case fatality rate (p = 0.003) were significantly lower in patients with meningitis than in those without meningitis. The odds of developing meningitis were higher in asplenic/hyposplenic or splenectomized patients (adjusted odds ratio [aOR] 2.29, 95% CI 1.27–4.14), for serotypes 10A (aOR 3.26, 95% CI 2.10–5.06) or 23A (aOR 3.91, 95% CI 2.47–6.19), but lower for those aged ≥ 65 years (aOR 0.59, 95% CI 0.44–0.81). PCV13 had an indirect effect on nonmeningitis, but its impact on meningitis was limited because of an increase in non-PCV13 serotypes. Of meningitis isolates, 78 (35.1%) and 3 (1.4%) were penicillin G- or ceftriaxone-resistant, respectively. We also confirmed an association of the pbp1bA641C mutation with meningitis (aOR 2.92, 95% CI 1.51–5.65).

Pediatric Parapneumonic Effusion/Pleural Empyema in Japan: A Nationwide Survey

BACKGROUND

Pediatric parapneumonic effusion/ pleural empyema (PPE/PE) is a severe infectious condition, and its management should be guided by local epidemiology and the patient's medical history. This survey aimed to determine the clinical and bacteriologic features of PPE/PE in Japan.

METHODS

A nationwide retrospective questionnaire survey was conducted, targeting 159 pediatric specialist training medical facilities for inpatients ≤18 years of age who were admitted for PPE/PE between January 2007 and December 2016.

RESULTS

Valid responses were obtained from 122 facilities, and 96 patients were identified from 38 facilities. The median age (interquartile range) was 2.7 (0.8-7.8) years. Overall, 60 (63 %) patients were men and 49 (51%) had comorbidities. The causative bacteria were identified in 59% of patients by culture except in one case identified using PCR. Streptococcus pyogenes (16%), Staphylococcus aureus (14%) and Streptococcus pneumoniae (13%) were the major pathogens. Carbapenems were administered to 34% of patients without comorbidities. Chest tube drainage was performed in 71%, intrapleural fibrinolytic therapy in 9.4%, surgery in 25% and mechanical ventilation in 29% of the patients. Five patients (5.2%) had complications and one (1.1%) had sequelae, but all patients (100%) survived.

CONCLUSIONS

This is first report of a nationwide survey pertaining to pediatric PPE/PE in Japan. We found that the etiology showed a different trend from that reported in other countries. It is worrisome that molecular methods were rarely used for pathogenic diagnosis and carbapenems were overused. Thus, it is imperative to establish clinical guidelines for PPE/PE in Japan.

Burden of illness associated with pneumococcal infections in Japan - a targeted literature review

INTRODUCTION

Pneumococcal diseases (PDs) are among the leading causes of mortality and morbidity worldwide. However, the evidence on epidemiology, health economic, and patient-reported outcomes has not been systematically reviewed and published in Japan. This study aimed to assess the burden, treatment adherence and compliance, and serotype distribution associated with PDs in Japan.

METHOD

One hundred and eight studies were identified between January 2005 and June 2020. The identified studies were mostly regional and with a limited scale, clinical settings, and populations.

RESULTS

In 2013-2017, invasive PD incidence rates were 4.98-9.47/100,000 in <4-year-olds, 0.36/100,000 in 5-14-year-olds, 0.46/100,000 in 15-64-year-olds, and 1.50-5.38/100,000 in the elderly. The incidence of invasive PDs in children decreased from 24.6/100,000 in 2008 to 10.7/100,000 in 2013 after the introduction of PCV7 and further declined to 10.3/100,000 in 2014 after PCV13 was introduced. From 2014, the prevalence of PCV13 serotypes decreased across all age groups along with a decrease of PPV23 serotypes, but an increase of PPV23 serotypes not included in PCV13 among adults and the elderly. No study reported health-related quality-of-life data for PDs. In children, direct costs were 340,905-405,978 JPY (3,099-3,691 USD) per pneumococcal bacteraemia, 767,447-848,255 JPY (6,977-7,711 USD) per pneumococcal meningitis, and 79,000 JPY (718 USD) per pneumococcal acute otitis media episodes. In adults and the elderly, the direct cost of pneumococcal pneumonia was 348,280-389,630 JPY (3,166-3,542 USD). The average hospital stay length was 7.2-31.9 days in children, 9.0 days in adults and 9.0-28.7 days in adults and the elderly.

CONCLUSIONS

The epidemiological burden of PDs remains high in Japan, especially among children and the elderly with invasive PDs accounting for a very small proportion of all PDs. A significant impact of the PCV13 vaccine program was reported, while the PPV23's impact remains unclear. A substantial decrease in quality-adjusted life years in adults and the elderly and a high economic burden may exist.

Whole-genome analysis-based phylogeographic investigation of Streptococcus pneumoniae serotype 19A sequence type 320 isolates in Japan

After the introduction of the seven-valent pneumococcal conjugate vaccine, the global spread of multidrug-resistant serotype 19A-sequence type 320 (ST320) strains of Streptococcus pneumoniae became a public health concern. In Japan, the main genotype of serotype 19A was ST3111, and the identification rate of ST320 was low. Although the isolates were sporadically detected in both adults and children, their origin remains unknown. Thus, by combining pneumococcal isolates collected in three nationwide pneumococcal surveillance studies conducted in Japan between 2008 and 2020, we analyzed 56 serotype 19A-ST320 isolates along with 931 global isolates, using whole-genome sequencing to uncover the transmission route of the globally distributed clone in Japan. The clone was frequently detected in Okinawa Prefecture, where the United States returned to Japan in 1972. Phylogenetic analysis demonstrated that the isolates from Japan were genetically related to those from the United States; therefore, the common ancestor may have originated in the United States. In addition, Bayesian analysis suggested that the time to the most recent common ancestor of the isolates from Japan and the U.S. was approximately the 1990s to 2000, suggesting the possibility that the common ancestor could have already spread in the United States before the Taiwan 19F-14 isolate was first identified in a Taiwanese hospital in 1997. The phylogeographical analysis supported the transmission of the clone from the United States to Japan, but the analysis could be influenced by sampling bias. These results suggested the possibility that the serotype 19A-ST320 clone had already spread in the United States before being imported into Japan.

A randomized phase 1 study of the safety and immunogenicity of 2 novel pneumococcal conjugate vaccines in healthy Japanese adults in the United States

Expanding serotype coverage of pneumococcal conjugate vaccines (PCVs) to target prevailing disease-causing serotypes could further reduce disease burden. To address this need, 2 different PCVs have been investigated: a 20-valent PCV (PCV20; includes the 13 serotypes in the 13-valent PCV [PCV13] plus 7 additional serotypes [8, 10A, 11A, 12F, 15B, 22F, 33F]) and a complementary 7-valent PCV (cPCV7; contains only the 7 additional serotypes). This phase 1b, randomized, controlled, double-blind study evaluated PCV20 and cPCV7 safety and immunogenicity in healthy Japanese adults 18–49 years of age residing in the United States for ≤5 years. Participants (n = 104) were randomized equally to receive a single dose of PCV20, cPCV7, or PCV13. Immunogenicity was assessed at baseline and 1 month after vaccination using serotype-specific opsonophagocytic activity (OPA) titers and serotype-specific immunoglobulin G (IgG) concentrations. Prompted local reactions and systemic events; adverse events (AEs); and serious AEs and newly diagnosed chronic disease were assessed 14 days, through 1 month, and upto 6 months following vaccination, respectively. OPA immune responses were robust for all 20 serotypes in the PCV20 group and for the 7 serotypes in the cPCV7 group 1 month after vaccination. IgG immune response showed similar trends. Injection site pain and muscle pain were the most common local reaction and systemic event; the majority were mild or moderate in severity. Few AEs and no severe AEs, serious AEs, or safety-related withdrawals were reported. Taken together, administration of PCV20 or cPCV7 in Japanese adults was well tolerated and induced robust serotype-specific functional immune responses. NCT03642847.

Pneumococcal serotype-specific IgG and opsonophagocytic activity in young Japanese patients with asplenia

Patients with asplenia are at high risks of severe infections caused by encapsulated bacteria, particularly Streptococcus pneumoniae. Thirteen-valent pneumococcal conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) are recommended for invasive pneumococcal disease prevention; however, little is known about the immunity to pneumococci in young patients with asplenia. We measured pneumococcal serotype-specific IgG (Pn-IgG) levels and pneumococcal opsonophagocytic activity (Pn-OPA) against some PCV13-contained serotypes (1, 3, 5, 6A, 7 F, 19A) in 23 young patients with asplenia using surplus serum samples. In this study, 5 and 13 patients had received PCV13 during routine immunizations and PPSV23, respectively; however, >5 years had passed since the last dose in most cases. The geometric mean concentrations (GMCs) of Pn-IgG in all study patients were not under the cutoff level against six serotypes, but they were lower than the those of age-matched healthy controls, as we have previously published. The patients who had received only PPSV23 had significantly lower GMCs against four serotypes (serotypes 1, 6A, 7 F, and 19A) than that of the patients who had received at least one PCV13 vaccination. The patients who had received only PPSV23 also had significantly lower geometric mean titers (GMTs) of Pn-OPA against all three serotypes we measured (serotypes 3, 5, and 19A) than that of the patients who had received at least one PCV13 vaccination. Our findings are useful data that can indicate insufficient immunity in young patients with asplenia against some PCV13 pneumococci serotypes and suggest the need for appropriate vaccinations in the post-PCV13 era.

The incremental burden of invasive pneumococcal disease associated with a decline in childhood vaccination using a dynamic transmission model in Japan: A secondary impact of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has disrupted childhood vaccinations, including pneumococcal conjugate vaccine (PCV). Evaluating the possible impact on the invasive pneumococcal disease (IPD) incidence associated with a decline in childhood pneumococcal vaccination is important to advocate the PCV programs. Using a deterministic, dynamic transmission model, the differential incidence and burden of IPD in children younger than 5 years in Japan were estimated between the rapid vaccination recovery (January 2021) and the delayed vaccination recovery (April 2022) scenarios for the next 10 years. In our model, the IPD incidence was reduced from 11.9/100,000 in 2019 to 6.3/100,000 in 2020, caused by a reduced transmission rate due to the COVID-19 mitigation measures. Assuming a recovery in the transmission rate in 2022 April, the incidence of IPD was estimated to increase with maximal incidence of 12.1 and 13.1/100,000 children under 5 years in the rapid and the delayed vaccination recovery scenarios. The difference in the total IPD incidence between these two scenarios was primarily driven by vaccine serotypes IPD incidence. The difference of incidence was not observed between the two scenarios after 2025. The persistent decline in childhood pneumococcal vaccination rates due to the impact of COVID-19 might lead to an increased IPD incidence and an incremental disease burden.

Interrupted time-series analyses of routine vaccination program for elderly pneumonia patients in Japan; an ecological study using aggregated nationwide inpatient data

A national routine pneumococcal pneumonia immunization program started in Japan in 2014. It targeted the population aged ≥65 years and used a 23-valent pneumococcal polysaccharide vaccine; PPSV23. However, its effectiveness was not well defined because of the lack of a comprehensive database on the PPSV23 vaccination status of each subject. We used interrupted time-series analyses to assess the changes in the incidence and prognosis of elderly patients hospitalized for pneumonia before and after initiation of the program. First, we estimated the PPSV23 coverage rates in subjects aged ≥65 years based on the number of shipped PPSV23 syringes and the estimated population in each prefecture. The estimated coverage rates reached around 40% in 2014 for the 3 Tohoku prefectures, while those in the other prefectures remained below 20%. After the national routine immunization program started, the estimated coverage rate increased significantly in every prefecture and exceeded 40% in 2017. Next, we aggregated the data extracted from the Japanese Diagnosis Procedure Combination database from April 2011 through February 2017 for hospitalized pneumonia patients aged ≥65 years. The data included data from 655,746 patients, excluding those in the 3 Tohoku prefectures. Interrupted time-series analyses found no change in the incidence of hospitalized pneumonia patients and in-hospital mortality after the vaccination program, but there was a decrease in the in-hospital mortality of pneumonia patients with severe comorbidities defined by the modified Charlson comorbidity index. These results suggest an association between the vaccination program and an improved outcome in hospitalized elderly pneumonia patients with severe comorbidities in Japan.

Risk factors of bacteremia in children hospitalized with community-acquired pneumonia: A nested case-control study

OBJECTIVE

To assess the risk factors of bacteremia in children hospitalized with community-acquired pneumonia (CAP).

STUDY DESIGN

The present, nested, case-control study enrolled a cohort of patients with CAP aged < 18 years who were hospitalized at Tokyo Metropolitan Children's Medical Center or Tama-Hokubu Medical Center between March 2010 and February 2018. Among the cohort with blood cultures (BCs), patients with bacteremia were identified and matched with five control patients based on their treatment facility, underlying disease, and age. Conditional logistic regression was used to calculate the odds ratios (ORs) of bacteremia for risk factor candidates.

RESULTS

BCs were obtained for 2,383 (84%) of the 2,853 patients in the CAP cohort. Of those with BCs, 34 (1.4%) had bacteremia. S. pneumoniae and H. influenzae accounted for 26 (76%) and four (12%) instances of the bacteremia pathogens, respectively. Bacteremia occurred more frequently among patients hospitalized in the spring than during other seasons (P = 0.022). On multivariate analysis, the severity of pneumonia was not associated with bacteremia incidence (OR: 0.92 [0.30-2.85]) while a white blood cell count > 16,000/μL (OR: 5.90 [2.14-16.3]) was shown to be a significant risk factor. The OR of the need for a ventilator on admission day was significantly high (28.4 [3.02-1374]) on univariate analysis, but the subject pool was too small to determine its significance on multivariate analysis.

CONCLUSIONS

The results of the present study supported BC collection in patients with leukocytosis and in those requiring ventilator use on admission.

Distribution and Variation of Serotypes and Pneumococcal Surface Protein A Clades of Streptococcus pneumoniae Strains Isolated From Adult Patients With Invasive Pneumococcal Disease in Japan

Pneumococcal surface protein A (PspA) is a surface protein of Streptococcus pneumoniae that may be a candidate antigen for new pneumococcal vaccines. This study investigates the distribution of PspA clades of the causative strains of adult invasive pneumococcal disease (IPD) in Japan. Of the 1,939 strains isolated from cases of adult IPD during 2014–2019, the PspA clades of 1,932 (99.6%) strains were determined, and no pspA was detected in the remaining 7 strains (0.4%). PspA clades 1–6 were detected in 786 (40.5%), 291 (15.0%), 443 (22.8%), 369 (19.0%), 33 (1.7%), and 6 (0.3%) strains, respectively. New PspA clades (0.2%) were identified in two non-typeable and two serotype 35B pneumococci. The proportions of clade 1 and clade 2 showed significantly decreased and increased trends, respectively. Furthermore, the PspA clade of pneumococcal strains was partially serotype- and sequence type-dependent. The majority of strains belonging to serotypes contained in both the 13-valent pneumococcal conjugate vaccine (PCV13) and the 23-valent pneumococcal polysaccharide vaccine (PPSV23) belonged to PspA clades 1 or 3. In contrast, the distribution of clades in non-vaccine serotypes was wider than that of vaccine serotype pneumococci. Our findings demonstrate that almost all pneumococcal strains from adult IPD express PspA clades 1–4, especially for non-vaccine serotypes. These results may be useful for the development of a new pneumococcal vaccine with PspA.

Bacteremia-Induced Cholestatic Jaundice as a Major Manifestation of Pneumococcal Infection in a Healthy Toddler

The development of pneumococcal conjugate vaccines has substantially decreased the incidence of invasive pneumococcal diseases. However, the incidence of bacteremia due to nonvaccine serotypes has increased. Therefore, it is important to recognize the symptoms and complications of pneumococcal infection to expedite diagnosis. Herein, we report the case of a 22-month-old patient diagnosed with pneumococcal bacteremia who presented with cholestatic jaundice and fever without any other signs of systemic sepsis. The patient's condition improved soon after antibacterial therapy. Other causes of jaundice were possibly ruled out based on the screening test for viral hepatitis, and there were no abnormal findings on abdominal ultrasonography. Therefore, the present case suggests that cholestatic jaundice could be a manifestation of pneumococcal bacteremia.

Drastic reduction in pneumococcal meningitis in children owing to the introduction of pneumococcal conjugate vaccines: Longitudinal analysis from 2002 to 2016 in Japan

INTRODUCTION

The characteristics of pneumococcal isolates and their associations with outcomes in pediatric meningitis are unclear. This study aimed to clarify serotypes and resistance genotypes of Streptococcus pneumoniae from children with meningitis and evaluate the patient prognoses and backgrounds.

METHODS

Large-scale surveillance was conducted from 2002 to 2016 through periods I-V. Serotypes and penicillin (PEN) resistance genotypes were analyzed for pneumococcal isolates (n = 459) and cerebrospinal fluid (CSF) samples (n = 25). Furthermore, underlying diseases (n = 251), prognoses (n = 202), and laboratory data were evaluated.

RESULTS

The number of meningitis cases decreased drastically after the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) to -53.6% and after switching to PCV13 to -70.2%. In particular, this reduction was apparent at ≤3 years of age. The proportion of the PCV7 serotype decreased sharply from 70.1% before introduction to 2.6% during period V; however, the non-vaccine type increased from 17.5% to 87.2%. The PEN resistance rate (gPRSP) was decreased from approximately 49% to 12.2% during period V. Among cases revealed prognosis, sequelae and mortality rates were 16.3% and 5.4%, respectively. The rate of the patients with underlying diseases was 26.3% and relatively high in ≥6 years. Laboratory data associated with a poor prognosis were low white blood cell count (<12.7 × 10³/μL), low platelet count (<28.1 × 10⁴/μL), low CSF-glucose (<36 mg/dL), and high CSF-protein (≥142 mg/dL).

CONCLUSIONS

Changes in serotype prevalence warrant continuous monitoring to observe future trends of pneumococcal meningitis, and further developments in multivalent conjugate vaccines are required.

Traditional Japanese Herbal Medicine Hochu-Ekki-to Promotes Pneumococcal Colonization Clearance via Macrophage Activation and Interleukin 17A Production in Mice

Streptococcus pneumoniae may colonize the nasopharynx, and as pneumococcal colonization causes invasive diseases and the subsequent transmission, reducing bacterial burden in the nasal cavity is critical. Hochu-ekki-to (TJ-41) is a traditional Japanese herbal medicine that exerts immunomodulatory effects in host cells. In this study, we investigated the potency of TJ-41 in modulating pneumococcal colonization clearance by activating host immunity. Mice, intranasally inoculated with pneumococci, were treated orally with TJ-41. During colonization, TJ-41 treatment significantly reduced pneumococcal burden and increased macrophage population in the nasopharynx. Furthermore, interleukin 17A production was significantly enhanced after TJ-41 treatment. In vitro experiment using nasal-derived cells revealed that pneumococcal antigen exposure upregulated the transcription of interleukin 17A in the TJ-41-treated group compared with that in the control group. Macrophages activated by killed bacteria were significantly increased in the presence of TJ-41 in an interleukin 17A-dependent manner. Moreover, TJ-41 enhanced phagocytosis, inhibited bacterial growth, and improved the antigen-presenting capacity of macrophages. Our results demonstrate that TJ-41 accelerates the clearance of pneumococcal nasopharyngeal colonization via macrophage activation. Subsequent production of interleukin 17A provides an additional benefit to effector cells.

Serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae associated with invasive pneumococcal disease among adults in Japan

OBJECTIVES

This study evaluated the serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae isolates from adults (aged ≥20 years) with invasive pneumococcal disease (IPD) in Japan.

METHODS

This prospective observational study was conducted in 49 participating Japanese hospitals. S. pneumoniae isolates were serotyped and tested for antimicrobial susceptibility at a central laboratory. Information regarding patient characteristics, underlying disease, IPD clinical syndromes, and treatment was collected through medical chart review.

RESULTS

The final analysis included 177 patients enrolled from 45 hospitals between September 2016 and April 2018 (bacteraemic pneumonia, 110; bacteraemia without identified focus, 29; meningitis, 19). Most patients (70.1%) were aged ≥65 years and most had underlying disease (79.1%). The proportion of isolates from serotypes contained in the pneumococcal polysaccharide vaccine (PPV) 23 was 61.0%, while those in the pneumococcal conjugate vaccine (PCV) 7 and PCV13 were 2.8% and 28.2%, respectively. Non-vaccine serotypes accounted for 37.9% of all isolates and 50.8% of isolates from immunosuppressed patients. Serotype 12F was the most common vaccine serotype, followed by serotype 3.

CONCLUSIONS

The continued disease burden of IPD in adults in Japan warrants improved vaccination rates and development of next-generation vaccines that include serotypes not currently covered.

CLINICAL TRIAL REGISTRATION

Clinical trial summary registration number 160,822,918,146; JapicCTI-163352.

Seroepidemiological analysis of anti-pneumococcal surface protein A (PspA) immunoglobulin G by clades in Japanese population

BACKGROUND

Pneumococcal surface protein A (PspA) is one of the candidates of the novel pneumococcal protein vaccines. The seroepidemiology of naturally acquired anti-PspA immunoglobulin G (IgG) by clades, across a wide range of ages has not been investigated.

METHODS

We examined the concentrations of anti-PspA IgG by clades (1, 2, 3, 4, and 5) in 397 sera from persons aged 0-≥70 years by enzyme-linked immunosorbent assay, and determined the geometric mean concentrations (GMCs) by age group. The relationships between concentrations of anti-PspA IgG antibody for each clade for each person were also assessed.

RESULTS

GMC of anti-PspA IgG was lowest, highest, and plateaued in those aged 6-11 months, 5-9-years, and 20-49 years, respectively. It gradually declined in those aged > 70 years. GMCs patterns in different age groups were similar for all clades. Correlations were found especially within the same PspA family (between clades 1 and 2 or clades 4 and 5).

CONCLUSIONS

Our data suggested that most people acquired anti-PspA IgG across clades 1, 2, 3, 4, and 5 during childhood. These results would be a fundamental data of clade-specific anti-PspA IgG antibodies.

Current situation and need for prevention of invasive pneumococcal disease and pneumococcal pneumonia in 6- to 64-year-olds in Japan

We conducted a systematic review of the literature to evaluate the reported epidemiology and burden of invasive pneumococcal disease (IPD) and pneumococcal pneumonia (PP) among children and adults aged 6-64 years in Japan. Studies published from Japan between September 2009 and September 2019 and indexed in the MEDLINE/PubMed or ICHUSHI databases were evaluated. A majority of the studies reported overlapping age ranges, including children aged <6 years and adults aged >64 years. According to the national surveillance data, 19% of the IPD cases were patients aged 5-59 years, and an increasing trend in IPD cases was reported from 2013 to 2017. Comorbidities were consistent with those reported by the Advisory Committee on Immunization Practices. Deaths from IPD appeared to increase nearly 3-fold between 2013 and 2017. Overall, both 13-valent pneumococcal conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) coverage was higher for IPD compared with PP. All the serotypes known to be prominent in Japan were also identified as common serotypes (3, 6A, 19A: PCV13 serotypes; 12F: outbreak serotype; 15A, 35B: drug-resistant serotypes). This systematic literature review suggests a substantial burden of IPD and PP in Japanese children and adults aged 6-64 years. The burden of comorbidities, hospitalizations, and mortality was particularly high among adults. Concerted pneumococcal vaccination strategies may help to reduce the incidence and burden of IPD and PP in this large proportion of the Japanese population.

National trends in appropriate antibiotics use among pediatric inpatients with uncomplicated lower respiratory tract infections in Japan

BACKGROUND

Japan was ranked as the worst country of 36 high-income countries in terms of oral antibiotic consumptions for children. Knowing the patterns and variations of antibiotic use for pediatric inpatients with uncomplicated respiratory infections is an important step to promote judicious antibiotic use.

METHODS

Discharge records were extracted for children aged between 3 months and 15 years with acute lower respiratory tract infections for the fiscal years 2010-2014 using a national inpatient database in Japan. We investigated the trends in antibiotic use using mixed effect regression models and ascertained variations and clustering of the practice patterns across different hospitals using unsupervised machine learning methodology.

RESULTS

A total of 280,298 children were included in the study. Total and broad-spectrum antibiotic use, except for fluoroquinolone, showed decreasing trends from 2010 to 2014. Additionally, the proportions of patients who received no antibiotics or only penicillin increased from 17.1% to 9.9% in 2010 to 24.5% and 13.7% in 2014, respectively. Cluster analysis showed that only one-quarter of hospitals used no antibiotics for 28.8% of children and only penicillin for 53.7% of children. In the remaining clusters of hospitals, the piperacillin, 3rd generation cephalosporins, and penicillin beta-lactamase inhibitors were used for 68.5%, 68.5%, and 69.6% of the patients who received antibiotics.

CONCLUSIONS

Slightly increasing trends in narrow-spectrum antibiotics were observed. However, the treatment strategy in only one-quarter of hospitals was consistent with the current recommendations. Hospital level interventions to promote and monitor antibiotic use could be helpful to improve antibiotic use for pediatric inpatients.

Genetic characteristics of piliated Streptococcus pneumoniae serotype 35B, increased after introduction of pneumococcal vaccines in Japan

INTRODUCTION

Streptococcus pneumoniae is a commensal bacterium of the human nasopharynx and a major causative pathogen of bacterial diseases worldwide. Pilus of S. pneumoniae is one of the virulence factors which enhance the adhesion to the host epitherial cells in the upper respiratory tract.

METHODS

We analyzed the serotype distribution and presence of pilus genes, rrgC and sipA, among 785 S. pneumoniae isolates from specimens of patients with invasive or non-invasive disease in a regional Japanese hospital between October 2014 and August 2018. We next performed multilocus sequence typing and penicillin-resistant genotyping for 86 isolates of serotype 35B.

RESULTS

Serotype 35B was the most frequent serotype which accounted for 11.0% of total isolates and had pilus genes at high rate (80.2%). Clonal complex (CC) 558 isolates accounted for 77.9% of serotype 35B and were highly positive for rrgC and gPRSP (98.5%). In contrast, all CC2755 isolates (19.8%) were rrgC-negative and gPISP.

CONCLUSIONS

Our results suggest that CC558 may assist the prevalence of serotype 35B after the introduction of vaccines, as that clone has pili as adhesins in addition to non-susceptibility against penicillin. These results may be useful information for development of optimal preventive strategies. Continuous studies on serotype distribution and virulence factors of S. pneumoniae are necessary.

Two cases of bacterial meningitis due to meropenem-resistant Streptococcus pneumoniae: A threat of serotype 35B, ST 558 lineage

Although the pneumococcal conjugate vaccine (PCV) has decreased the incidence of invasive pneumococcal disease (IPD) in children, cases of IPD caused by non-PCV serotypes have been increasing. Here, we report two cases of bacterial meningitis caused by meropenem-resistant Streptococcus pneumoniae; in both the cases, 13-valent PCV (PCV13) had been administered. The isolated S. pneumoniae strains were non-PCV13 serotype 35B and resistant to penicillin G, cefotaxime, and meropenem. In addition, multilocus sequence typing (MLST) revealed the sequence type (ST) to be 558. In case 1, a 6-month-old girl recovered without sequelae after antibiotic therapy comprising cefotaxime and vancomycin, whereas in case 2, a 9-month-old boy was treated with an empirical treatment comprising ceftriaxone and vancomycin administration. However, maintaining the blood concentration of vancomycin within the effective range was difficult, due to which the antibiotics were changed to panipenem/betamipron. During the treatment, he presented with seizures, which were effectively controlled with antiepileptic drugs. The rate of incidence of penicillin-susceptible IPD has been substantially increasing after the introduction of PCV. However, an upsurge in IPD cases due to multidrug-resistant (MDR) serotype 35B has been reported in countries where PCV13 was introduced before introducing in Japan. Moreover, an increase in the proportion of MDR serotype 35B and decrease in the susceptibility to broad-spectrum antimicrobials, including meropenem, have been reported. Hence, the number of meningitis cases caused by MDR serotype 35B/ST558 may increase in the future.

Hemophagocytic lymphohistiocytosis complicating invasive pneumococcal disease: a pediatric case report

Background

Hemophagocytic lymphohistiocytosis (HLH) is an infrequent but life-threatening disease due to excessive immune activation. Secondary HLH can be triggered by infections, autoimmune diseases, and malignant diseases. Streptococcus pneumoniae is a pathogenic bacterium responsible for invasive pneumococcal disease (IPD) such as meningitis and bacteremia. Although the pneumococcal conjugate vaccine (PCV) has led to reductions in IPD incidence, cases of IPD caused by serotypes not included in PCV are increasing. There are few reports of secondary HLH caused by IPD in previously healthy children. We herein report a rare case of a previously healthy boy with secondary HLH complicating IPD of serotype 23A, which is not included in the pneumococcal 13-valent conjugate vaccine (PCV-13).

Case presentation

An 11-month-old boy who had received three doses of PCV-13 was hospitalized with prolonged fever, bilateral otitis media, neutropenia and elevated C-reactive protein (CRP) levels. Blood culture on admission revealed S. pneumoniae, leading to a diagnosis of IPD. HLH was diagnosed based on a prolonged fever, neutropenia, anemia, hepatosplenomegaly, hemophagocytosis in the bone marrow, and elevated serum levels of triglycerides, ferritin, and soluble interleukin-2 receptor. He received broad-spectrum antibiotics and intravenous immunoglobulins for IPD and high-dose steroid pulse therapy and cyclosporine A for HLH; thereafter, his fever resolved, and laboratory findings improved. The serotype of the isolated S. pneumoniae was 23A, which is not included in PCV-13.

Conclusions

It is important to consider secondary HLH as a complication of IPD cases with febrile cytopenia or hepatosplenomegaly, and appropriate treatment for HLH should be started without delay.

Concurrent Bacteremia Due to Non-vaccine Serotype 24F Pneumococcus in Twins: A Rapid Increase in Serotype 24F-invasive Pneumococcal Disease and its High Invasive Potential

Although concurrent bacteremia in siblings is rare, serotype 24F Streptococcus pneumoniae was isolated from the blood of twin 1-year-old girls within a 3-day interval, supporting the high invasive potential of this serotype. As the prevalence of childhood serotype 24F-invasive pneumococcal diseases increases in Europe and the Western Pacific Region, investigation and surveillance of this serotype are necessary.

Epidemiological and molecular characterization of invasive Streptococcus pneumoniae isolated following introduction of 7-valent conjugate vaccine in Kinki region, Japan, 2008-2013

Streptococcus pneumoniae is one of the most common bacteria causing community-acquired pneumonia and meningitis. The use of 7-valent pneumococcal conjugate vaccine (PCV7) has reduced the incidence of pneumococcal disease while changing pneumococcal population through herd immunity and non-vaccine pneumococci replacement. This study investigated molecular epidemiologic characteristics of pneumococcal strains in the Kinki region of Japan from 2008 to 2013. A total of 159 invasive pneumococcal isolates were characterized by serotyping, antibiotic susceptibility testing, PCR analysis of penicillin-binding protein genes, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). In adult populations, pediatric PCV7 introduction decreased isolates expressing PCV7 serotypes via herd immunity and increased isolates expressing non-PCV7 serotypes. The rate of penicillin resistance and isolates with alterations in all three pbp genes was higher in PCV7 type isolates than in non-PCV7 type isolates. In MLST analysis, all of serotype 19F isolates were of the same sequence type, ST236, which is the antimicrobial-resistant clone Taiwan^19F-14, and the majority of serotypes 23F and 19A isolates were of ST1437 and ST3111 respectively, which are the predominant clones of antimicrobial-resistant pneumococci in Japan. In PFGE profiles, serotype 6B-ST2224, serotype 19F-ST236, serotype 19A-ST3111, and serotype 23F-ST1437 formed six separate clusters composed of genetically identical strains, and genetically identical serotype 22F-ST433 formed two different clusters between the pre- and post-PCV7 period. The results of molecular analysis suggest the spread and persistence of these identical antimicrobial resistant clones in the Kinki region and genetic changes of epidemic clone serotype 22F-ST433 before and after pediatric PCV7 introduction.

Nationwide surveillance of paediatric invasive and non-invasive pneumococcal disease in Japan after the introduction of the 13-valent conjugated vaccine, 2015-2017

Streptococcus pneumoniae is still one of the major causes of morbidity and mortality worldwide. In Japan, pneumococcal conjugate vaccine (PCV)7 and PCV13 were licensed in 2010 and 2013, respectively. We conducted a nationwide paediatric invasive pneumococcal disease (IPD) and non-IPD surveillance study in Japan between 2015 and 2017. We collected 498 IPD isolates and 231 non-IPD isolates from a total of 187 medical institutions in Japan. We performed serotyping, antimicrobial susceptibility testing and multi-locus sequencing typing (MLST) for the collected isolates. Among the 498 IPD isolates, the most prevalent serotype was 24F, followed by 12F, 15A and 15B/C. However, 12F increased and 24F significantly decreased during the study period (p < 0.001), resulting in 12F becoming the most prevalent serotype in 2017. Among the IPD isolates, the PCV7 and PCV13 coverage rates were 0.8% and 9.2%, respectively. The most prevalent serotype among the non-IPD isolates was 15A, followed by 35B, 15B/C and 19A. The overall resistance rates to penicillin (PG), cefotaxime (CTX), meropenem (MEM), erythromycin (EM) and levofloxacin (LFX) were 40.5%, 12.2%, 19.4%, 91.8% and 0.5%, respectively. PG, CTX and MEM resistance rates were significantly higher in non-IPD isolates than in IPD isolates (p < 0.001). Serotype 15A-CC63 and serotype 35B-CC558 tended to be multi-drug resistant. In conclusion, the PCV13 coverage rate was significantly lower than that in a previous surveillance study in Japan between 2012 and 2014, and IPD cases attributable to serotype 19A also decreased. We should note the rapid increase in the prevalence of serotype 12F in IPD cases and the spread of the multi-drug resistant serotype 15A-CC63 and 35B-CC558 lineages.

Clonal spread of serotype 12F ST4846 Streptococcus pneumoniae

Introduction. In 2016-2017, there was an increase in the number of paediatric invasive pneumococcal disease (IPD) cases caused by Streptococcus pneumoniae serotype 12F in Chiba Prefecture, Japan. Serotype 12F is one of the major causative serotypes of IPD following the introduction of pneumococcal conjugate vaccine 13 (PCV13), and outbreaks of IPD caused by serotype 12F have recently been reported in several countries.Aim. Our goal here was to clarify the relationship among local outbreak strains and the outbreak strains in other countries, and for this we analysed clinical isolates of S. pneumoniae serotype 12F using several genetic identification methods.Methodology. All reported IPD cases caused by serotype 12F were reviewed and bacterial strains were collected and analysed. We also analysed S. pneumoniae serotype 12F strains isolated from other time periods, geographical areas, cases of adult IPD and respiratory specimens as control strains. Multi-locus sequence typing, PFGE and multi-locus variable number tandem repeat analysis (MLVA) were conducted on all isolates.Results. All 26 S. pneumoniae serotype 12F isolates, including control strains, belonged to a single sequence type (ST4846) that was the specific ST in Japan. All tested strains demonstrated five MLVA patterns and two PFGE patterns.Conclusion. We determined that the 2016-2017 outbreak of IPD in Chiba Prefecture was caused by clonally related isolates of serotype 12F. The continuous monitoring of IPD caused by serotype 12F is important for evaluating the impact of re-emerging pneumococcal serotypes following the PCV13 introduction era, and MLVA could be a useful tool for identification of outbreak strains.

Molecular typing, antibiotic susceptibility, and biofilm production in nonencapsulated Streptococcus pneumoniae isolated from children in Japan

The prevalence of nonencapsulated Streptococcus pneumoniae (NESp) has increased with the introduction of pneumococcal conjugate vaccines in children; however, the bacteriological characteristics of NESp have not been sufficiently clarified. In this study, NESp strains isolated from the nasopharyngeal carriage of children from four nursery schools in Japan were analyzed for molecular type, antibiotic susceptibility, and biofilm productivity. A total of 152 putative S. pneumoniae strains were identified by optochin-susceptibility analysis, of which 21 were not serotypeable by slide agglutination, quellung reaction, or multiplex PCR. Among these 21 strains, three were lytA-negative and, therefore, not S. pneumoniae. The remaining 18 strains were positive for lytA, ply, pspK, and bile solubility and were confirmed as NESp. Therefore, the isolation rate of NESp in the S. pneumoniae strains in this study was 12.0% (18/149). Molecular-typing analyses classified five strains as two existing sequence types (STs; ST7502 and ST7786), and 13 strains formed four novel STs. Horizontal spread was suspected, because strains with the same ST were often isolated from the same nursery school. The NESp isolates were generally susceptible to most antimicrobials, with the exception of macrolides; however, all isolates possessed more than one abnormal penicillin-binding protein gene. Furthermore, NESp strains were more effective than encapsulated counterparts at forming biofilms, which showed obvious differences in morphology. These data indicated that NESp strains should be continuously monitored as emerging respiratory pathogens.

Assessment of the local clonal spread of Streptococcus pneumoniae serotype 12F caused invasive pneumococcal diseases among children and adults

BACKGROUND

We conducted active surveillance to elucidate the distribution of Streptococcus pneumoniae serotypes causing invasive pneumococcal disease (IPD) and clarified the genetic relatedness among the isolates in Kobe City, Japan.

METHODS

Forty-five IPD-causing S. pneumoniae strains were analyzed from March 2016 to May 2018 through active surveillance in Kobe City, Hyogo, Japan. Serotypes were determined by multiplex serotyping PCR and the Quellung reaction with pneumococcal antisera. Fourteen Sp12F strains were subjected to whole-genome sequencing (WGS).

RESULTS

Among 45 isolates, the most frequent serotypes were 12F (n=14, 31%), 24F (n=5, 11%), and 10A (n=4, 9%). Multilocus sequence typing (MLST) analysis of 14 isolates of Sp12F divided them into ST4846 (n=4) and ST6495 (n=10). WGS showed clonality of the 10 isolates of ST6495, with only 13 single nucleotide polymorphisms in the genomes. Meanwhile, ST4846 strains in Kobe differed from only the outbreak strains of Sp12F ST4846 in Tsuruoka, Japan, reported on 2018.

CONCLUSIONS

Serotype monitoring showed Sp12F to be the predominant serotype in Kobe, and WGS revealed the clonal spread of Sp12F ST6495 in this city. Thus, the spread of Sp12F could become a serious public health problem in Japan, warranting thorough monitoring in future.

Whole-Genome Sequencing Analysis of Multidrug-Resistant Serotype 15A Streptococcus pneumoniae in Japan and the Emergence of a Highly Resistant Serotype 15A-ST9084 Clone

Since the introduction of pneumococcal conjugate vaccines (PCVs), an increase in the incidence of disease attributable to serotype 15A-ST63 (sequence type 63) pneumococci has been observed in many regions worldwide. We conducted a nationwide pediatric pneumococcal infection surveillance study between 2012 and 2014 in Japan. In the surveillance study, we detected multidrug-resistant serotype 15A-CC63 (clonal complex 63) strains (resistant to macrolides, penicillin, cefotaxime, and meropenem); in this study, we analyzed these resistant isolates to determine the dynamics and mechanism of resistance using whole-genome sequencing. In most of the penicillin-, cefotaxime-, and meropenem-resistant strains, recombination occurred in the pbp2x region, resulting in the acquisition of cefotaxime resistance in addition to penicillin and meropenem resistance. In the multidrug-resistant serotype 15A-CC63 strains, we identified a specific clone with ST9084, and all of the isolates were recovered from the Yamaguchi prefecture in Japan. All of the serotype 15A-ST9084 isolates had a novel pbp2x type (pbp2x-JP3) that was inserted by recombination events. The conserved amino acid motif profiles of pbp1a, pbp2b, and pbp2x of the strains were identical to those of serotype 19A-ST320. A Bayesian analysis-based date estimation suggested that this clone emerged in approximately 2002 before the introduction of the PCV in Japan. This clone should be monitored because serotype 15A is not contained in the currently used 13-valent PCV (PCV13), and it was resistant to beta-lactams, which are often used in a clinical setting.

The Incidence of Pediatric Invasive Bacterial Diseases in Nippon Medical School Chiba Hokusoh Hospital before and after the Introduction of Conjugate Vaccines

The introduction of the Haemophilus influenzae type b (Hib) vaccine and the 7-valent pneumococcal conjugate vaccine (PCV7) has led to dramatic reductions in cases of invasive H. influenzae disease and invasive pneumococcal disease (IPD). After the introduction of the PCV7 and the 13-valent pneumococcal conjugate vaccine (PCV13), the number of children with IPD markedly decreased in our hospital. However, since 2015, three children with IPD have been admitted to our hospital. We analyzed the serotype, multilocus sequence type, and antimicrobial susceptibility of Streptococcus pneumoniae strains isolated in these newly diagnosed cases. The strains were serotypes 7F and 12F. In addition, we analyzed the incidence of invasive bacterial disease before and after the introduction of conjugate vaccines and found no change in the incidences. We found that cases of IPD and invasive H. influenzae disease clearly decreased following the introduction of the PCV7, the PCV13, and the Hib vaccine, as well as disease caused by antibiotic-resistant strains.

Local outbreak of Streptococcus pneumoniae serotype 12F caused high morbidity and mortality among children and adults

Pneumococcal serotype replacement is an important issue after the introduction of pneumococcal conjugate vaccine (PCV) in children. After the introduction of 13-valent PCV, the incidence of invasive pneumococcal diseases (IPD) caused by Streptococcus pneumoniae serotype 12F (Sp12F) have increased in some countries; however, an outbreak of Sp12F has not reported in the post-13-valent PCV era. We experienced a local outbreak of Sp12F during March through May 2016 in Tsuruoka city, Japan after the introduction of 13-valent PCV in 2013. The IPD patients were two children and seven adults, three of whom died with a rapid disease progress. Although the clear transmission route was not determined, eight of the nine patients (89%) had close contact with children, which suggests that transmitted colonisation of Sp12F among children and adults might be the source of transmission. Continuous monitoring of IPDs, along with the determination of pneumococcal serotypes, is warranted in the post-13-valent PCV era. New IPD control strategies may be needed if this fatal outbreak continues to occur.

Clinical and Bacteriologic Analysis of Nontypeable Haemophilus influenzae Strains Isolated from Children with Invasive Diseases in Japan from 2008 to 2015

Haemophilus influenzae type b (Hib) conjugate vaccines have led to dramatic reductions in Hib disease among young children worldwide. Nontypeable H. influenzae (NTHi) is now the major cause of invasive H. influenzae infections. We investigated the clinical characteristics of invasive NTHi diseases among children in Japan, to clarify the pathogenicity of isolated NTHi strains. The mortality rate was 10.7%, with deaths occurring mainly among children with underlying comorbidities. Biotypes II and III were the most common, and most strains (64.3%) had multiple amino acid substitutions at the Asp-350, Ser-357, Ser-385, and/or Met-377 sites of penicillin-binding protein 3. Two strains were β-lactamase positive and ampicillin-clavulanate resistant. Biofilm indices varied widely, and IS1016 was detected in 10.7% of the strains tested. Moreover, there was wide variation in the characteristics of invasive NTHi strains. NTHi strains, showing great genetic diversity, are responsible for most invasive H. influenzae infections in children in the postvaccine era. Continuous monitoring of NTHi strains responsible for invasive diseases in children is important to detect changes in the epidemiology of invasive H. influenzae infections in the postvaccine era.

Genetic diversity of pneumococcal surface protein A (PspA) in paediatric isolates of non-conjugate vaccine serotypes in Japan

PURPOSE

Among the pneumococcal proteins, pneumococcal surface protein A (PspA) is considered the most promising candidate for a serotype-independent vaccine. This study aimed to investigate the serotype, genetic diversity of PspA, lineage (genotype) and drug resistance traits of pneumococcal isolates from paediatric patients.

METHODOLOGY

A total of 678 non-invasive pneumococcal isolates obtained from June to November 2016 were analysed. All isolates were characterized for PspA families, serotypes and macrolide resistance genes. Seventy-one representative isolates of non-vaccine serotypes (NVTs) were genetically analysed for the clade-defining region (CDR) of PspA, as well as multi-locus sequence typing (MLST).

RESULTS

The detection rate of NVTs was 87.9 % (n=596), including dominant NVTs 15A (14.5 %, n=98), 35B (11.8 %, n=80), 15C (9.3 %, n=63) and 23A (9.0 %, n=61). Most isolates (96.6 %) possessed macrolide resistance genes erm(B) and/or mef(A/E). PspA families 1, 2 and 3 were detected in 42.3, 56.6 and 0.6 % of isolates, respectively. Nucleotide sequences of CDR showed high identity (90-100 %) within the same PspA clade, although the CDR identity among different PspA families ranged from 53 to 69 %. All isolates of NVTs 23A, 10A, 34, 24, 22F/22A, 33F, 23B and 38 were from PspA family 1, while NVTs 35B, 15C, 15B and 11A/11D isolates were from family 2. In contrast, genetically distinct PspAs were found in NVTs 6C and 15A. PspA family 3/clade 6 was detected in only NVT serotype 37 isolates assigned to ST447 and ST7970, showing the mucoid phenotype.

CONCLUSION

The present study revealed the predominance of PspA families 1 and 2 in NVTs, and the presence of family 3 in serotype 37.

Serotype replacement of Streptococcus pneumoniae due to seven-valent pneumococcal conjugate vaccine in Japan

BACKGROUND

This study examined the trends for the serotypes of S. pneumoniae that have caused infections before (2010) and after (2012) the introduction of PCV-7 in Japan.

METHODS

We examined 458 strains of Streptococcus pneumoniae obtained from 22 pediatric institutions throughout Japan from January to June 2010 (immediately after the introduction of the seven-valent pneumococcal conjugate vaccine [PCV-7]), and 370 strains obtained from 19 institutions from January to June 2012 (after PCV-7 became widely used). The samples were collected from children aged 0-14 years with conditions such as respiratory tract infections (upper airway inflammation, bronchitis, and pneumonia), meningitis, and sepsis.

RESULTS

The most frequent serotype in the 2010 strains was 19F (17.3%), followed by 6B (16.8%), and 23F (15.1%). The most frequent serotype in the 2012 strains was 6C (10.0%), followed by 19F (9.7%), 15A (8.9%) and 15B (8.9%), indicating a significant change in the distribution. The serotypes contained in PCV-7 were detected in 280 strains (61.1%) in 2010 and in 81 strains (21.9%) in 2012 (P < 0.01). The serotypes contained in PCV-13 were detected in 356 strains (77.7%) in 2010 and in 146 strains (39.5%) in 2012 (P < 0.01). A total of 129 subjects who had not been vaccinated with PCV-7 and 127 subjects who had been vaccinated with PCV-7 at least once, were compared with regard to the 2012 strains. The serotypes contained in PCV-7 were found in 21 strains (16.5%) in those who had been vaccinated and in 37 strains (28.7%) in those who had not been vaccinated (P < 0.05).

CONCLUSIONS

The increased use of PCV-7 led to decreases in the serotypes contained in PCV-13 and increases in the serotypes not contained in PCV-13, suggesting serotype replacement.

Pneumococcal polysaccharide vaccination in allogeneic hematopoietic stem cell transplantation recipients: a prospective single-center study

Few studies have evaluated the response of allogeneic hematopoietic stem cell transplantation [allo-HSCT] recipients to pneumococcal polysaccharide vaccine-23 [PPSV23] in the modern transplant era when more elderly patients undergo allo-HSCT. We administered a single dose of PPSV23 to 30 allo-HSCT recipients and evaluated serotype-specific antibody responses using IgG measured by enzyme-linked immunosorbent assay and opsonophagocytic assay [OPA] titers in a multiplexed opsonophagocytic killing assay. The median patient age was 54 years [range, 23-68], and the interval from allo-HSCT to vaccination was 756 days [range, 389-1903]. No severe adverse effects were observed. The median positive response rates at 1 month and 1 year post-vaccination for the 7 serotypes measured by IgG were the same at 43% [range, 33-57], while those for 8 serotypes measured by OPA were 72% [range, 55-86] and 55% [range, 52-62], respectively. Peripheral blood stem cell transplantation improved vaccine response based on OPA titers at 1 month post-vaccination. During the median follow-up period of 1135 days post-vaccination, one patient developed pneumococcal bacteremia at 998 days. Our study suggests that PPSV23 vaccination in allo-HSCT recipients is safe and may result in a serological response.

Comparison of traditional culture and molecular qPCR for detection of simultaneous carriage of multiple pneumococcal serotypes in African children

S. pneumoniae is a common colonizer of the human nasopharynx in high income and low-middle income countries. Due to limitations of standard culture methods, the prevalence of concurrent colonization with multiple serotypes is unclear. We evaluated the use of multiplex quantitative PCR (qPCR) to detect multiple pneumococcal serotypes/group colonization in archived nasopharyngeal swabs of pneumococcal conjugate vaccine naive children who had previously been investigated by traditional culture methods. Overall the detection of pneumococcal colonization was higher by qPCR (82%) compared to standard culture (71%; p < 0.001), with a high concordance (kappa = 0.73) of serotypes/groups identified by culture also being identified by qPCR. Also, qPCR was more sensitive in detecting multiple serotype/groups among colonized cases (28.7%) compared to culture (4.5%; p < 0.001). Of the additional serotypes detected only by qPCR, the majority were of lower density (<10⁴ CFU/ml) than the dominant colonizing serotype, with serotype/group 6A/B, 19B/F and 23F being the highest density colonizers, followed by serotype 5 and serogroup 9A/L/N/V being the most common second and third colonizers respectively. The ability of qPCR to detect multiple pneumococcal serotypes at a low carriage density might provide better insight into underlying mechanism for changes in serotype colonization in PCV vaccinated children.

Serotype distribution of Streptococcus pneumoniae causing invasive disease in children in the post-PCV era: A systematic review and meta-analysis

BACKGROUND

Routine immunisation with pneumococcal conjugate vaccines (PCV7/10/13) has reduced invasive pneumococcal disease (IPD) due to vaccine serotypes significantly. However, an increase in disease due to non-vaccine types, or serotype replacement, has been observed. Serotypes' individual contributions to IPD play a critical role in determining the overall effects of PCVs. This study examines the distribution of pneumococcal serotypes in children to identify leading serotypes associated with IPD post-PCV introduction.

METHODS

A systematic search was performed to identify studies and surveillance reports (published between 2000 and December 2015) of pneumococcal serotypes causing childhood IPD post-PCV introduction. Serotype data were differentiated based on the PCV administered during the study period: PCV7 or higher valent PCVs (PCV10 or PCV13). Meta-analysis was conducted to estimate the proportional contributions of the most frequent serotypes in childhood IPD in each period.

RESULTS

We identified 68 studies reporting serotype data among IPD cases in children. We analysed data from 38 studies (14 countries) where PCV7 was administered and 20 (24 countries) where PCV10 or PCV13 have been introduced. Studies reported early and late periods of PCV7 administration (range: 2001∓13). In these settings, serotype 19A was the most predominant cause of childhood IPD, accounting for 21.8% (95%CI 18.6∓25.6) of cases. In countries that have introduced higher valent PCVs, study periods were largely representative of the transition and early years of PCV10 or PCV13. In these studies, the overall serotype-specific contribution of 19A was lower (14.2% 95%CI 11.1∓18.3). Overall, non-PCV13 serotypes contributed to 42.2% (95%CI 36.1∓49.5%) of childhood IPD cases. However, regional differences were noted (57.8% in North America, 71.9% in Europe, 45.9% in Western Pacific, 28.5% in Latin America, 42.7% in one African country, and 9.2% in one Eastern Mediterranean country). Predominant non-PCV13 serotypes overall were 22F, 12F, 33F, 24F, 15C, 15B, 23B, 10A, and 38 (descending order), but their rank order varied by region.

CONCLUSION

Childhood IPD is associated with a wide number of serotypes. In the early years after introduction of higher valent PCVs, non-PCV13 types caused a considerable proportion of childhood IPD. Serotype data, particularly from resource-limited countries with high burden of IPD, are needed to assess the importance of serotypes in different settings. The geographic diversity of pneumococcal serotypes highlights the importance of continued surveillance to guide vaccine design and recommendations.

Pediatric bacterial meningitis in Japan, 2013-2015 - 3-5 years after the wide use of Haemophilus influenzae type b and Streptococcus pneumoniae conjugated vaccines

BACKGROUND

Haemophilus influenzae type b (Hib) vaccine and pneumococcal conjugated vaccine (PCV) have been widely used since 2010 in Japan when both vaccines were supported by the regional governments, and they were covered as routine recommended vaccines in 2013. The incidence of bacterial meningitis due to these organisms decreased in 2011 and 2012, but meningitis due to Streptococcus agalactiae and Escherichia coli remained unchanged.

OBJECTIVES

We planned to confirm whether the incidence also decreased in subsequent years.

METHODS

We analyzed the epidemiological and clinical data for 2013-2015, and compared the information obtained in the previous nationwide survey database and our previous reports. We also investigated the risk factors for disease outcome.

RESULTS

In the 2013-2015 surveys, 407 patients from 366 hospitals from all prefectures were evaluated. S. agalactiae (33%), Streptococcus pneumoniae (25%), and E. coli (10%) were the main organisms. The total number of patients hospitalized with bacterial meningitis per 1000 admissions decreased from 1.19 in 2009-2010 to 0.37 in 2013-2015 (p < 0.001). The incidence of H. influenzae and S. pneumoniae meningitis significantly decreased from 0.66 in 2009-2010 to 0.01 in 2013-2015, and from 0.30 to 0.09, respectively (p < 0.001). Only 0-2 cases with Neisseria meningitidis were reported each year throughout 2001-2015. The fatality rates for H. influenzae, S. pneumoniae, S. agalactiae, and E. coli in 2013-2015 were 0.0, 4.1, 3.1, and 2.6%, respectively. Risk factors for death and sequelae were consciousness disturbance, convulsion, low CSF glucose, and Staphylococcus sp. as a causative organism (p < 0.01).

CONCLUSIONS

Hib vaccine and PCV have decreased the rate of bacterial meningitis. S. agalactiae has subsequently become the most common cause of bacterial meningitis in Japan.

Rise of multidrug-resistant non-vaccine serotype 15A Streptococcus pneumoniae in the United Kingdom, 2001 to 2014

Conjugate vaccines have reduced pneumococcal disease in vaccinated children and unvaccinated adults, but non-vaccine serotypes are of concern, particularly if antibiotic resistant. We reviewed Streptococcus pneumoniae collected via: (i) the British Society for Antimicrobial Chemotherapy (BSAC) surveillances from 2001–2014; (ii) Public Health England’s (PHE) invasive isolate surveillance from 2005–2014 and (iii) referral to PHE for resistance investigation from 2005–2014. Serotype 15A increased in all series, with many representatives showing triple resistance to macrolides, tetracyclines and penicillin. 15A was consistently among the 10 most prevalent serotypes from 2011 in PHE and BSAC invasive isolate/bacteraemia surveillance but never previously; 26–33% of these invasive 15A isolates had triple resistance. BSAC respiratory isolates were only serotyped in 2013/14 and 2014/15 (October to September); 15A was most prevalent serotype in both periods, comprising 9–11% of isolates, 38–48% of them with triple resistance. Serotype 15A represented 0–4% of S. pneumoniae referred to PHE for reference investigation annually until 2008 but rose to 29% (2013) and 32% (2014). Almost all multidrug-resistant 15A isolates were sequence type (ST) 63 variants, whereas susceptible 15A isolates were clonally diverse. The rise of serotype 15A suggests that pneumococcal conjugate vaccines will need ongoing adaptation.

First report of serotype 23B Streptococcus pneumoniae isolated from an adult patient with invasive infection in Japan

Serotype 23B Streptococcus pneumoniae was isolated from a 67-year-old Japanese patient with meningitis. This isolate was susceptible to penicillin G, while genotyped as gPISP with a mutation in a penicillin-binding motif in PBP2b. The 23B isolate was assigned to ST11996 that is related to CC439, a dominant group among serotype 23B.

Pneumococcal vaccination reduces the risk of community-acquired pneumonia in children

BACKGROUND

The seven-valent pneumococcal conjugate vaccine (PCV7) was introduced to Japan in 2009, after which there was a rapid decline in invasive pneumococcal disease. There are few data, however, on the effectiveness of PCV7 against community-acquired pneumonia (CAP). We conducted an ambispective cohort study among children aged 0-6 years old who attended day-care centers.

METHODS

A total of 624 children at 10 day-care centers in Sapporo, Japan participated in the study. The parents reported whether their child had received PCV7 one or more times, as well as the exact dates of vaccination from records in maternal and child health handbooks marked by pediatricians. Each CAP event was reported by parents according to doctor diagnosis. A Cox proportional hazards regression model was used to calculate the hazard ratio (HR) and 95%CI of CAP incidence reduced by PCV7 inoculation.

RESULTS

During the observational period, 94 subjects contracted CAP. After adjusting for potentially confounding variables, inoculation with PCV7 was significantly associated with a reduced risk of CAP (HR, 0.22; 95%CI: 0.13-0.34). On stratified analysis by age, PCV7 was significantly associated with a reduced risk of CAP in both children aged <3 years (HR, 0.31; 95%CI: 0.14-0.71), and those ≥3 years (HR, 0.20; 95%CI: 0.09-0.43).

CONCLUSION

PCV7 is highly effective in reducing the risk of CAP in children attending day-care centers.