Epidemiology of childhood invasive pneumococcal disease in Australia: a prospective cohort study

BACKGROUND

The widespread use of pneumococcal conjugate vaccines (PCV) has changed the epidemiology of invasive pneumococcal disease (IPD) in children globally.

METHODS

Multicentre prospective audit of IPD episodes from five paediatric hospitals in Australia over 5.5 years between 2016 and June 2021. Children (<18 years) with Streptococcus pneumoniae isolated from a sterile site were included.

RESULTS

There were 377 IPD episodes in 375 children: 338 (90%) had received ≥3 PCV doses; 42 (11%) had IPD risk factors. The most common presentations were complicated pneumonia (254, 67%), bacteraemia (65, 17%) and meningitis (29, 8%). Five (1%) children died.Serotype information was available for 230 (61%) episodes; 140 (61%) were 13vPCV vaccine serotypes (VTs). The majority (85%) of episodes of complicated pneumonia were due to a VT; predominantly 3, 19A, 19F. Children with risk factors were more likely to present with bacteraemia ± sepsis (42% vs 12%) and to have a non-vaccine serotype (NVT) (74% vs 32%). Resistance to ceftriaxone (meningitis cut-off) occurred in 17% of 23B isolates (n=12) and accounted for 22% (5/23) of meningitis cases.

CONCLUSIONS

Complicated pneumonia is the most common IPD presentation. NVTs account for the majority of bacteraemia and meningitis episodes. High rates of ceftriaxone resistance for NVT 23B support the addition of vancomycin for empiric treatment of suspected meningitis.

Estimated impact of revising the 13-valent pneumococcal conjugate vaccine schedule from 2+1 to 1+1 in England and Wales: A modelling study

BACKGROUND

In October 2017, the United Kingdom Joint Committee on Vaccination and Immunisation (JCVI) recommended removal of one primary dose of the 13-valent pneumococcal conjugate vaccine (PCV13) from the existing 2+1 schedule (2, 4, 12 months). We conducted a mathematical modelling study to investigate the potential impact of a 1+1 (3, 12 month) schedule on invasive pneumococcal disease (IPD) and pneumococcal community-acquired pneumonia (CAP). Our results and those from a 1+1 immunogenicity study formed the key evidence reviewed by JCVI.

METHODS AND FINDINGS

We developed age-structured, dynamic, deterministic models of pneumococcal transmission in England and Wales to describe the impact on IPD of 7-valent PCV (PCV7; introduced in 2006) and PCV13 (introduced in 2010). Key transmission and vaccine parameters were estimated by fitting to carriage data from 2001/2002 and post-PCV IPD data to 2015, using vaccine coverage, mixing patterns between ages, and population data. We considered various models to investigate potential reasons for the rapid increase in non-PCV13 (non-vaccine serotype [NVT]) IPD cases since 2014. After searching a large parameter space, 500 parameter sets were identified with a likelihood statistically close to the maximum and these used to predict future cases (median, prediction range from 500 parameter sets). Our findings indicated that the emergence of individual NVTs with higher virulence resulting from ongoing replacement was likely responsible; the NVT increase was predicted to plateau from 2020. Long-term simulation results suggest that changing to a 1+1 schedule would have little overall impact, as the small increase in vaccine-type IPD would be offset by a reduction in NVT IPD. Our results were robust to changes in vaccine assumptions in a sensitivity analysis. Under the base case scenario, a change to a 1+1 schedule in 2018 was predicted to produce 31 (6, 76) additional IPD cases over five years and 83 (-10, 242) additional pneumococcal-CAP cases, with together 8 (-2, 24) additional deaths, none in children under 15 years. Long-term continuation with the 2+1 schedule, or changing to a 1+1, was predicted to sustain current reductions in IPD cases in under-64-year-olds, but cases in 65+-year-olds would continue to increase because of the effects of an aging population. Limitations of our model include difficulty in fitting to past trends in NVT IPD in some age groups and inherent uncertainty about future NVT behaviour, sparse data for defining the mixing matrix in 65+-year-olds, and the methodological challenge of defining uncertainty on predictions.

CONCLUSIONS

Our findings suggest that, with the current mature status of the PCV programme in England and Wales, removing one primary dose in the first year of life would have little impact on IPD or pneumococcal CAP cases or associated deaths at any age. A reduction in the number of priming doses would improve programmatic efficiency and facilitate the introduction of new vaccines by reducing the number of coadministered vaccines given at 2 and 4 months of age in the current UK schedule. Our findings should not be applied to other settings with different pneumococcal epidemiology or with immature programmes and poor herd immunity.

Comparative incidence dynamics and serotypes of meningitis, bacteremic pneumonia and other-IPD in young children in the PCV era: Insights from Israeli surveillance studies

INTRODUCTION

Widespread introduction of pneumococcal conjugated vaccines (PCVs) impacted on invasive pneumococcal disease (IPD). However, IPD reduction may not be similar in all outcomes within IPD. We assessed PCV7/PCV13 impact on pneumococcal meningitis, bacteremic pneumonia (BP) and other (non-meningitis, non-pneumonia) IPD episodes in children <5years in Israel.

METHODS

A prospective, population-based, active nationwide surveillance. All pneumococcal invasive episodes with positive blood/CSF cultures, July 2000 through June 2016, were included. Three sub-periods were defined: pre-PCV (2000-2008), PCV7 (2009-2011) and PCV13 (2014-2016). Incidence rate ratios (IRRs) were calculated.

RESULTS

Overall, 4321 episodes were recorded; 456 (10.6%) meningitis, 1478 (34.2%) pneumonia and 2387 (55.2%) other-IPD. In the pre-PCV period, proportion of serotypes in PCV13, but not in PCV7 (mainly serotypes 1, 5 and 19A) was higher in BP (43.3%) compared with other-IPD episodes (32.8%, p<0.001) and similar to that of meningitis (37.6%, p=0.1). The proportion of episodes in children <12months was higher in meningitis (52.1%) compared with pneumonia (23.2%) and other-IPD episodes (39.5%; p<0.001 for both). The declines of the 3 entities were not similar; Meningitis rate non-significantly declined by 24% (IRR=0.76; 95% CI 0.57-1.01), while BP and other-IPD rates significantly declined by 57% and 70%, respectively. In contrast to other entities, BP did not decline significantly after PCV7 introduction but started to decline only after PCV13 introduction. Rates of meningitis, pneumonia and other-IPD caused by PCV13-serotypes (VT13) substantially declined by 88%, 95% and 97%, respectively, comparing PCV13 and the pre-PCV periods. However, diseases caused by non-VT13 increased by 256%, 302% in meningitis and pneumonia, respectively, but only 116% in other-IPD.

CONCLUSIONS

Following PCV7/PCV13 introduction, rates of episodes caused by VT13 were substantially reduced in all 3 groups. However, differences in age distribution, serotype replacement and specific serotype decrease suggest different pathogenesis and host susceptibility between the 3 entities.

Pneumococcal Disease in the Era of Pneumococcal Conjugate Vaccine

Universal immunization of infants and toddlers with pneumococcal conjugate vaccines over the last 15 years has dramatically altered the landscape of pneumococcal disease. Decreases in invasive pneumococcal disease, all-cause pneumonia, empyema, mastoiditis, acute otitis media, and complicated otitis media have been reported from multiple countries in which universal immunization has been implemented. Children with comorbid conditions have higher rates of pneumococcal disease and increased case fatality rates compared with otherwise healthy children, and protection for the most vulnerable pediatric patients will require new strategies to address the underlying host susceptibility and the expanded spectrum of serotypes observed.

Comparative impact of pneumococcal conjugate vaccines on pneumococcal meningitis according to underlying conditions

BACKGROUND

Several underlying conditions increase the risk of pneumococcal meningitis (PM) in childhood. Patients with these diseases are initially considered as an important target of pneumococcal conjugate vaccines (PCVs). Limited data are available for PM in children with underlying conditions. To understand the benefits of PCV7 followed by PCV13 in this vulnerable population, we analyzed the data for a large cohort of pediatric patients with PM in France from 2001 to 2014.

METHODS

We conducted hospital-based active surveillance with 227 pediatric wards working with 168 microbiology departments throughout France. Standardized inclusion criteria for PM were used and data were analyzed by a pre-PCV7, post-PCV7 and post-PCV13 period.

RESULTS

From 2001 to 2014, among the 1582 cases of PM, 62.5% were reported in children less than 2years old. Underlying conditions (n=255, 16.1%) accounted for 7.3% of the cases in these young children versus 30.8% for children ⩾2-18years old (p<0.001). After PCV13 implementation, PM cases decreased by 44.0% from 2009 to 2014, mainly in children without underlying conditions. Though the number of children with underlying conditions remained stable, their proportion among overall PM cases increased by 79.1%. Among children with underlying conditions, PCV7 serotypes, 6 additional PCV13 serotypes, additional 11 serotypes in PPV23 and other serotypes accounted for 24.5%, 14.7%, 25.0% and 35.8%, respectively (p<0.001). After PCV13 implementation, 50.0% of PM cases with underlying conditions and 37.9% without underlying conditions were caused by serotypes included in neither PCV13 nor PPV23.

CONCLUSION

Besides the reduced numbers of PM, its profile has changed, with an increase in cases in proportion of children with underlying conditions accompanied by a striking change in serotype distribution. This underlines the importance of detecting underlying conditions in children with PM in the PCV13 era.

Immunisation of the immunocompromised child

Immunocompromised children have a higher risk of developing infections and associated higher rates of mortality and morbidity. Although this group could benefit the most from vaccine administration, specific considerations regarding immunisations are required. This review is a summary of the vaccines that are relevant to the immunocompromised host, covering both live and non-live vaccines. The burden of disease, safety, immunogenicity/effectiveness and specific recommendations for each vaccine are described as well as specific guidelines from different organisations.

Incidence of invasive pneumococcal disease in 5-15 year old children with and without comorbidities in Germany after the introduction of PCV13: Implications for vaccinating children with comorbidities

OBJECTIVE

To describe the burden of suffering from IPD in children aged 5-15 years with and without comorbidities up to 5 years after the introduction of PCV13 in Germany and to identify the potential benefit for PCV13 and PPV23 vaccination.

METHODS

The surveillance of IPD for children <16 years was based on two independently reporting sources: active surveillance in pediatric hospitals and a laboratory-based sentinel surveillance system.

CASE DEFINITION

IPD with cultural detection of pneumococci at a physiologically sterile site in children from 2010 to 2014 in Germany. Incidence was estimated by capture-recapture analysis with stratification by absence/presence of comorbidities. Coverage of the observed serotypes by different vaccines was assessed.

RESULTS

142 (Capture recapture-corrected: 437) cases were reported: 72.5% were healthy children and 27.5% had a comorbidity. The incidence of IPD related to children with comorbidities was 0.2 per 100,000. One third of these cases had serotypes not included in either vaccine. The remaining cases might benefit from pneumococcal vaccination but one third of all cases was not vaccinated. The additional potential benefit of PPV23 compared to PCV13 with respect to coverage was 10%.

CONCLUSION

The incidence of IPD in children with comorbidities in Germany is low. Pneumococcal vaccination uptake in children with comorbidities should be increased, although only about two-thirds of the cases might be preventable by presently available vaccines.

PHiD-CV induces anti-Protein D antibodies but does not augment pulmonary clearance of nontypeable Haemophilus influenzae in mice

BACKGROUND

A recently-licensed 10-valent pneumococcal conjugate vaccine (PHiD-CV; Synflorix, GSK) uses Protein D from Haemophilus influenzae as a carrier protein. PHiD-CV therefore has the potential to provide additional protection against nontypeable H. influenzae (NTHi). NTHi frequently causes respiratory tract infections and is associated with significant morbidity and mortality worldwide and there is currently no vaccine.

METHODS

We developed mouse models of NTHi infection and influenza/NTHi superinfection. Mice were immunized with PHiD-CV, heat-killed NTHi, or a 13-valent pneumococcal conjugate vaccine that did not contain Protein D (PCV13; Prevenar, Pfizer) and then infected intranasally with NTHi.

RESULTS

Infection with NTHi resulted in weight loss, inflammation and airway neutrophilia. In a superinfection model, prior infection with pandemic H1N1 influenza virus (strain A/England/195/2009) augmented NTHi infection severity, even with a lower bacterial challenge dose. Immunization with PHiD-CV produced high levels of antibodies that were specific against Protein D, but not heat-killed NTHi. Immunization with PHiD-CV led to a slight reduction in bacterial load, but no change in disease outcome.

CONCLUSIONS

PHiD-CV induced high levels of Protein D-specific antibodies, but did not augment pulmonary clearance of NTHi. We found no evidence to suggest that PHiD-CV will offer added benefit by preventing NTHi lung infection.

Vaccination, underlying comorbidities, and risk of invasive pneumococcal disease

OBJECTIVES

Children with underlying conditions remain at increased risk for invasive pneumococcal diseases (IPD). This study describes the epidemiology, serotype distribution, clinical presentations, and outcomes of IPD in children with and without comorbidity.

METHODS

Cases of childhood IPD in Massachusetts were identified via enhanced surveillance from 2002 through 2014. Demographic and clinical data were collected via follow-up telephone interviews with parents and/or primary care providers. Underlying conditions were classified according to the 2012 Report of the Committee on Infectious Diseases and 2013 recommendations by the Advisory Committee on Immunization Practices.

RESULTS

Among 1052 IPD cases in Massachusetts children <18 years old, 22.1% had at least 1 comorbidity. Immunocompromising conditions (32.7%) and chronic respiratory diseases (22.4%) were most common. Children with comorbidities were older at the time of IPD diagnosis (median 54 vs 23 months, P < .001), had higher hospitalization (odds ratio 2.5; 95% confidence interval 1.7-3.6) and case-fatality rates (odds ratio 3.7; 95% confidence interval 1.5-8.9) compared with children without known underlying conditions after adjusting for age, gender, year of diagnosis, and pneumococcal vaccination status. During the last 2 years of the study, IPD among children with comorbidities was caused by non-pneumococcal conjugate vaccine 13 serotypes in 23-valent polysaccharide pneumococcal vaccine (6/12, 50%) or serotypes that are not included in any of the vaccines (6/12; 50%).

CONCLUSIONS

In children with comorbidity, IPD results in higher mortality, and a large proportion of disease is due to serotypes not included in current conjugate vaccines. Further research is needed, specifically to develop and evaluate additional strategies for prevention of IPD in the most vulnerable children.

Invasive pneumococcal disease after implementation of 13-valent conjugate vaccine

OBJECTIVE

To examine whether there is a different clinical profile and severity of invasive pneumococcal disease (IPD) in children caused by nonvaccine types in the era of 13-valent pneumococcal conjugate vaccine (PCV13).

METHODS

Observational study of childhood IPD in Massachusetts based on state public health surveillance data comparing pre-PCV13 (2007-2009) and post-PCV13 (2010-2012) eras.

RESULTS

There were 168 pre-PCV13 cases of IPD and 85 post-PCV13 cases of IPD in Massachusetts children ≤5 years of age. PCV13 serotypes declined by 18% in the first 2 years after PCV13 use (P = .011). In the post-PCV13 phase, a higher proportion of children were hospitalized (57.6% vs. 50.6%), and a higher proportion of children had comorbidity (23.5% vs. 19.6%). Neither difference was statistically significant, nor were comparisons of IPD caused by vaccine and nonvaccine types. Children with comorbidities had higher rates of IPD caused by a nonvaccine type (27.6% vs. 17.2%; P = .085), were more likely to be hospitalized (80.4% vs. 50%; P < .0001), and were more likely to have a longer hospital stay (median of 3 days vs. 0.5 days; P = .0001).

CONCLUSIONS

Initial data suggest that nonvaccine serotypes are more common in children with underlying conditions, who have greater morbidity from disease. In the post-PCV13 era, a larger proportion of patients are hospitalized, but mortality rates are unchanged. Routine vaccination with PCV13 may not be enough to reduce the risk in patients with comorbidity.