Long-term Impact of a "3 + 0" Schedule for 7- and 13-Valent Pneumococcal Conjugate Vaccines on Invasive Pneumococcal Disease in Australia, 2002-2014

Assessing the Impact of Pneumococcal Conjugate Vaccine Immunization Schedule Change From 3+0 to 2+1 in Australian Children: A Retrospective Observational Study

BACKGROUND

In mid-2018, the Australian childhood 13-valent pneumococcal conjugate vaccine schedule changed from 3+0 to 2+1, moving the third dose to 12 months of age, to address increasing breakthrough cases of invasive pneumococcal disease (IPD), predominantly in children aged >12 months. This study assessed the impact of this change using national IPD surveillance data.

METHODS

Pre- and postschedule change 3-dose 13-valent pneumococcal conjugate vaccine breakthrough cases were compared by age group, serotype, and clinical syndrome. Annual rates of breakthrough cases were calculated (per 100 000) using respective birth cohort sizes and 3-dose vaccine coverage. Using time-series modelling, observed IPD rates in children aged <12 years were compared to that expected if the 3+0 schedule were continued.

FINDINGS

Over 2012-2022, rate of 3-dose breakthrough cases in children aged >12 months was 2.8 per 100 000 (n = 557; 11 birth cohorts). Serotype 3 replaced 19A as predominant breakthrough serotype (respectively, 24% and 65% in 2013 to 60% and 20% in 2022) followed by 19F. In breakthrough cases, the most frequent clinical phenotype was bacteremic pneumonia (69%), with meningitis accounting for 3%-4%. In cohorts eligible for 2+1 versus 3+0 schedules, rate of breakthrough cases was lower for all vaccine serotypes, except type 3 (incidence rate ratio, 0.50 [95% confidence interval, .28-.84] and 1.12 [0.71-1.76], respectively). Observed compared to expected IPD was 51.7% lower (95% confidence interval, -60.9 to -40.7%) for vaccine serotypes, but the change for nonvaccine types was not significant 12% (-9.6 to 39.7).

INTERPRETATIONS

The 2+1 schedule is likely superior to 3+0 for overall IPD control, a finding that may be worth consideration for other countries considering or using 3+0 PCV schedules.

Effects of PCV10 and PCV13 on pneumococcal serotype 6C disease, carriage, and antimicrobial resistance

BACKGROUND

The cross-protection of pneumococcal conjugate vaccines (PCV) against serotype 6C is not clearly documented, although 6C represents a substantial burden of pneumococcal disease in recent years. A systematic review by the World Health Organization that covered studies through 2016 concluded that available data were insufficient to determine if either PCV10 (which contains serotype 6B but not 6A) or PCV13 (containing serotype 6A and 6B) conferred protection against 6C.

METHODS

We performed a systematic review of randomized controlled trials and observational studies published between January 2010 - August 2022 (Medline/Embase), covering the direct, indirect, and overall effect of PCV10 and PCV13 against 6C invasive pneumococcal disease (IPD), non-IPD, nasopharyngeal carriage (NPC), and antimicrobial resistance (AMR).

RESULTS

Of 2548 publications identified, 112 were included. Direct vaccine effectiveness against 6C IPD in children ranged between 70 and 85 % for ≥ 1 dose PCV13 (n = 3 studies), was 94 % in fully PCV13 vaccinated children (n = 2), and -14 % for ≥ 1 dose of PCV10 (n = 1). Compared to PCV7, PCV13 efficacy against 6C NPC in children was 66 % (n = 1). Serotype 6C IPD rates or NPC prevalence declined post-PCV13 in most studies in children (n = 5/6) and almost half of studies in adults (n = 5/11), while it increased post-PCV10 for IPD and non-IPD in all studies (n = 6/6). Changes in AMR prevalence were inconsistent.

CONCLUSIONS

In contrast to PCV10, PCV13 vaccination consistently protected against 6C IPD and NPC in children, and provided some level of indirect protection to adults, supporting that serotype 6A but not 6B provides cross-protection to 6C. Vaccine policy makers and regulators should consider the effects of serotype 6A-containing PCVs against serotype 6C disease in their decisions.

Impact of pneumococcal conjugate vaccination on pneumococcal nasopharyngeal carriage in the Gambia: Population-based cross-sectional surveys

BACKGROUND

The introduction of pneumococcal conjugate vaccines (PCV) has reduced carriage of vaccine-type (VT) pneumococci in many settings. We determined the impact of The Gambia's national PCV programme on carriage of VT pneumococci in the population.

METHODS

Seven-valent PCV (PCV7) was introduced in August 2009 without catch-up and with doses scheduled at 2, 3, 4 months of age; it was replaced by PCV13 in May 2011. We did cross-sectional carriage surveys in 2009, 2015, and 2017 in age-stratified, population-based samples. Nasopharyngeal specimens were collected and processed according to WHO guidelines. We calculated observed and adjusted prevalence ratios (PR) of VT carriage before and after PCV introduction.

FINDINGS

We enrolled 2988, 3162, and 2709 participants in 2009, 2015, and 2017 respectively. The baseline (2009) prevalence of VT pneumococcal carriage among children aged 0-4 years was 42.6 %, which declined to 14.9 % and 17.5 % in 2015 and 2017 respectively (adjPR 0.32 [95 % CI 0.27, 0.38] and 0.38 [0.31, 0.46] respectively). VT prevalence among children aged 5-14 years was 16.6 %, 15.1 %, and 15.8 % in the three surveys (2017 vs 2009, adjPR 0.70 [0.58, 0.83]). VT prevalence among 15-44 year-olds was 6.4 %, 5.7 %, and 7.1 % in the three surveys (2017 vs 2009, adjPR 0.59 [0.46, 0.75]), while in those aged ≥ 45 years it was 4.5 %, 6.5 %, and 4.5 % respectively. Non-VT carriage increased in all age-groups. Prevalent residual serotypes were 34 and 15B (age 0-4 years), 3 and 34 (age 5-14 years), and 3 and 16F (age ≥ 15 years).

CONCLUSIONS

Introduction of PCV was associated with reduced VT pneumococcal carriage in young, and older children, although with substantial residual prevalence. Persisting VT, and non-VT, carriage indicate significant, persistent transmission of pneumococci in the population.

A randomized, open-label, phase 3 study evaluating safety and immunogenicity of 13-valent pneumococcal conjugate vaccine in Chinese infants and children under 6 years of age

Streptococcus pneumoniae causes a considerable disease burden among children in China. Many isolates exhibit antimicrobial resistance but are often serotypes covered by the 13-valent pneumococcal conjugate vaccine (PCV13). Because the approved infant immunization schedule in China allows PCV13 vaccination only for those 6 weeks to 15 months of age, this phase 3 study was conducted to evaluate PCV13 immunogenicity and safety in unvaccinated older infants and children. Eligible participants were stratified by age into four cohorts: Cohort 1 (n = 125), 6 weeks-2 months; Cohort 2 (n = 354), 7-<12 months; Cohort 3 (n = 250), 1 -<2 years; Cohort 4 (n = 207), 2-<6 years. Cohort 1 received PCV13 at ages 2, 4, and 6 months; older cohorts were randomized 2:1 to PCV13 or Haemophilus influenzae type b (Hib) vaccine using age-appropriate schedules. Within-group immune responses were assessed by immunoglobulin G (IgG) concentrations and opsonophagocytic activity (OPA) titers. Safety evaluations included solicited reactogenicity events and adverse events (AEs). IgG geometric mean concentrations and OPA geometric mean titers for all 13 PCV13 serotypes increased for all participants vaccinated with PCV13, but not those vaccinated with Hib. Immune responses in Cohorts 2-4 were generally comparable with those in Cohort 1 (the infant series) for most serotypes. PCV13 was well tolerated across cohorts, with reported AEs consistent with expectations in these age groups; no new safety signals were identified. These results suggest that PCV13 administered as a catch-up regimen to infants and children 7 months-<6 years of age in China will effectively reduce vaccine-type pneumococcal disease in this population. NCT03574389.

Coverage of 13-Valent Pneumococcal Conjugate Vaccine Among Children 0-15 Months of Age - 9 Provinces, China, 2019-2021

What is already known on this topic?

Limited data exist regarding the coverage of the 13-valent pneumococcal conjugate vaccine (PCV13) in China. A lack of official statistics, coupled with an insufficient body of published literature, hinders the accurate depiction of the current situation.

What is added by this report?

This study investigated the utilization of PCV13 and estimated its coverage in nine provinces across eastern, central, and western China between 2019 and 2021. Despite an annual increase in PCV13 usage during this period, the overall coverage remained suboptimal.

What are the implications for public health practice?

Consideration should be given to incorporating vaccines into the Expanded Program of Immunization, reducing vaccine prices, and addressing the vaccination coverage gap between eastern and western regions when there is an adequate supply of PCV13, particularly with domestic vaccines.

Waning of antibody levels induced by a 13-valent pneumococcal conjugate vaccine, using a 3 + 0 schedule, within the first year of life among children younger than 5 years in Blantyre, Malawi: an observational, population-level, serosurveillance study

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) induce serotype-specific IgG antibodies, effectively reducing vaccine-serotype carriage and invasive pneumococcal disease (IPD). IgG production wanes approximately 1 month after vaccination in absence of serotype-specific exposure. With uncertainty surrrounding correlate of protection (CoP) estimates and with persistent vaccine-serotype carriage and vaccine-serotype IPD after PCV13 introduction, we aimed to profile population-level immunogenicity among children younger than 5 years in Blantyre, Malawi.

METHODS

For this serosurveillance study, we used a random subset of samples from a prospective population-based serosurvey in Blantyre, Malawi, done between Dec 16, 2016, and June 27, 2018. Sample selection was based on age category optimisation among children younger than 5 years, adequate sample volume, and available budget. We measured serotype-specific IgGs against the 13 vaccine serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) and two non-vaccine serotypes (12F and 33F), as well as IgGs against three pneumococcal proteins (PsaA, NanA, and Ply), using ELISA and a direct-binding electrochemiluminescence-based multiplex assay. We estimated population-level, serotype-specific immunogenicity profiles using a linear spline regression model. Analyses included samples stratified to 20 3-month age strata (eg, age <3 months to 57-59 months).

FINDINGS

We evaluated 638 plasma samples: 556 primary samples and 82 unique secondary samples (each linked to one primary sample). Immunogenicity profiles revealed a consistent pattern among vaccine serotypes except serotype 3: a vaccine-induced IgG peak followed by waning to a nadir and subsequent increase in titre. For serotype 3, we observed no apparent vaccine-induced increase. Heterogeneity in parameters included age range at post-vaccination nadir (from 11·2 months [19A] to 27·3 months [7F]). The age at peak IgG titre ranged from 2·69 months (5) to 6·64 months (14). Titres dropped below CoPs against IPD among nine vaccine serotypes (1, 3, 4, 5, 6B, 7F, 9V, 18C, and 23F) and below CoPs against carriage for ten vaccine serotypes (1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F, and 23F). Increasing antibody concentrations among older children and seroincident events were consistent with ongoing vaccine-serotype exposure.

INTERPRETATION

A 3 + 0 PCV13 schedule with high uptake has not led to sustained population-level antibody immunity beyond the first year of life. Indeed, post-vaccine antibody concentrations dropped below putative CoPs for several vaccine serotypes, potentially contributing to persistent vaccine-serotype carriage and residual vaccine-serotype IPD in Malawi and other similar settings. Policy decisions should consider alternative vaccine strategies, including a booster dose, to achieve sustained vaccine-induced antibody titres, and thus control.

FUNDING

Bill & Melinda Gates Foundation, Wellcome UK, and National Institute for Health and Care Research.

Changing Trends of Invasive Pneumococcal Disease in the Era of Conjugate Pneumococcal Vaccination in Olmsted County: A Population-Based Study

OBJECTIVE

To estimate the incidence of invasive pneumococcal disease (IPD) in the pre-13-valent pneumococcal conjugate vaccine (pre-PCV13; 7-valent pneumococcal conjugate vaccine era, 2002-2010) and post-PCV13 (2011-2018) time periods.

PATIENTS AND METHODS

Using the Rochester Epidemiology Project, we conducted a population-based cohort study of all IPD cases in Olmsted County, Minnesota, from January 1, 2002, to December 31, 2018.

RESULTS

Overall, 187 cases of IPD were identified. The incidence of IPD decreased significantly from 11.1 (95% CI, 9.1 to 13.2) to 5.6 (95% CI, 4.3 to 6.9) per 100,000 person-years when the pre- and post-PCV13 periods (2002-2010 vs 2011-2018) were compared (P<.001). Of the 187 patients with IPD, 112 (59.9%) had previously received at least 1 dose of pneumococcal vaccine. Among the IPD cases in the post-PCV13 period, there was an increase in non-PCV13 serotypes, mainly 11A (from 1.0% [1 of 105] to 6.2% [4 of 64]) and 33F (from 2.9% [3 of 105] to 15.6% [10 of 64]), while PCV13/non-7-valent pneumococcal conjugate vaccine serotypes declined from 38.1% (40 of 105) to 15.6% (10 of 64). At 30 days after an IPD diagnosis, the survival rate was 88.8% (95% CI, 84.4% to 93.4%).

CONCLUSION

A marked decline in IPD incidence occurred during the post-PCV13 era. Because of the observed increase in non-PCV13 serotypes, coupled with multiple factors that impact the epidemiology of IPD, ongoing surveillance of patients with IPD, particularly due to non-PCV13 serotypes, is warranted.

Kinetics of pneumococcal antibodies among HIV-exposed, uninfected infants in Botswana

BACKGROUND

Streptococcus pneumoniae is a leading cause of severe infections among children. Despite vaccination, HIV-exposed, uninfected (HEU) children have a higher incidence of invasive pneumococcal disease than HIV-unexposed, uninfected (HUU) children. We sought to compare the immunogenicity of 13-valent pneumococcal conjugate vaccine (PCV-13) in HEU and HUU infants.

METHODS

We conducted a prospective cohort study of 134 mother-infant dyads in Botswana. Infants received PCV-13 doses at 2, 3, and 4 months through routine clinical care. We measured IgG antibodies specific to vaccine serotypes in sera collected from infants at 0, 5, and 12 months of age. We calculated the proportion of infants with protective IgG levels (≥0.35 µg/mL) to specific pneumococcal serotypes.

RESULTS

At birth, fewer than half of infants had protective IgG levels to serotypes 1 (38%), 3 (46%), 4 (33%), 5 (23%), 6B (40%), 7F (44%), 9 V (44%), and 23F (46%). Compared to HUU infants (n = 97), HEU infants (n = 37) had lower antibody concentrations at birth to serotypes 5 (p = 0.046) and 19A (p = 0.008) after adjustment for maternal age and infant birth weight. More than 80% of HEU and HUU infants developed protective antibody levels to each of the 13 vaccine serotypes following PCV-13 vaccination. Median concentrations of antibodies to pneumococcal serotypes declined by 55-93% between 5 and 12 months of age, with fewer than half of infants having protective antibody levels to serotypes 1 (47%), 3 (28%), 9 V (44%), 18C (24%), and 23F (49%) at 12 months of age.

CONCLUSIONS

Both HEU and HUU infants developed protective antibody responses to PCV-13 administered in a 3 + 0 schedule. However, antibody concentrations to many pneumococcal serotypes waned substantially by 12 months of age, suggesting that a PCV-13 booster dose in the second year of life may be needed to maintain protective pneumococcal antibody levels in older infants and young children.

A cluster-randomised, non-inferiority trial of the impact of a two-dose compared to three-dose schedule of pneumococcal conjugate vaccination in rural Gambia: the PVS trial

BACKGROUND

Pneumococcal conjugate vaccines (PCV) effectively prevent pneumococcal disease but the global impact of pneumococcal vaccination is hampered by the cost of PCV. The relevance and feasibility of trials of reduced dose schedules is greatest in middle- and low-income countries, such as The Gambia, where PCV has been introduced with good disease control but where transmission of vaccine-type pneumococci persists. We are conducting a large cluster-randomised, non-inferiority, field trial of an alternative reduced dose schedule of PCV compared to the standard schedule, the PVS trial.

METHODS

PVS is a prospective, cluster-randomised, non-inferiority, real-world field trial of an alternative schedule of one dose of PCV scheduled at age 6 weeks with a booster dose at age 9 months (i.e. the alternative '1 + 1' schedule) compared to the standard schedule of three primary doses scheduled at 6, 10, and 14 weeks of age (i.e. the standard '3 + 0' schedule). The intervention will be delivered for 4 years. The primary endpoint is the population-level prevalence of nasopharyngeal vaccine-type pneumococcal carriage in children aged 2 weeks to 59 months with clinical pneumonia in year 4 of the trial. Participants and field staff are not masked to group allocation while measurement of the laboratory endpoint will be masked. Sixty-eight geographic population clusters have been randomly allocated, in a 1:1 ratio, to each schedule and all resident infants are eligible for enrolment. All resident children less than 5 years of age are under continuous surveillance for clinical safety endpoints measured at 11 health facilities; invasive pneumococcal disease, radiological pneumonia, clinical pneumonia, and hospitalisations. Secondary endpoints include the population-level prevalence of nasopharyngeal vaccine-type pneumococcal carriage in years 2 and 4 and vaccine-type carriage prevalence in unimmunised infants aged 6-12 weeks in year 4. The trial includes components of mathematical modelling, health economics, and health systems research.

DISCUSSION

Analysis will account for potential non-independence of measurements by cluster, comparing the population-level impact of the two schedules with interpretation at the individual level. The non-inferiority margin is informed by the 'acceptable loss of effect' of the alternative compared to the standard schedule. The secondary endpoints will provide substantial evidence to support the interpretation of the primary endpoint. PVS will evaluate the effect of transition from a standard 3+ 0 schedule to an alternative 1 + 1 schedule in a setting of high pneumococcal transmission. The results of PVS will inform global decision-making concerning the use of reduced-dose PCV schedules.

TRIAL REGISTRATION

International Standard Randomised Controlled Trial Number 15056916 . Registered on 15 November 2018.

Pneumococcal conjugate vaccination schedules in infants-acquisition, immunogenicity, and pneumococcal conjugate and yellow fever vaccine co-administration study

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) effectively prevent pneumococcal disease, but the global impact of pneumococcal vaccination is hampered by its cost. The evaluation of reduced dose schedules of PCV includes measurement of effects on immunogenicity and carriage acquisition compared to standard schedules. The relevance and feasibility of trials of reduced dose schedules is greatest in middle- and low-income countries, such as The Gambia, where the introduction of PCV resulted in good disease control but where transmission of vaccine-type pneumococci persists. We designed a large cluster-randomised field trial of an alternative reduced dose schedule of PCV compared to the standard schedule, the PVS trial. We will also conduct a sub-study to evaluate the individual-level effect of the two schedules on carriage acquisition, immunogenicity, and co-administration of PCV with yellow fever vaccine, the PVS-AcqImm trial.

METHODS

PVS-AcqImm is a prospective, cluster-randomised trial of one dose of PCV scheduled at age 6 weeks with a booster dose at age 9 months (i.e. alternative '1+1' schedule) compared to three primary doses scheduled at 6, 10, and 14 weeks of age (i.e. standard '3+0' schedule). Sub-groups within the alternative schedule group will receive yellow fever vaccine separately or co-administered with PCV at 9 months of age. The primary endpoints are (a) rate of nasopharyngeal vaccine-type pneumococcal acquisition from 9 to 14 months of age, (b) geometric mean concentration of vaccine-type pneumococcal IgG at 18 months of age, and (c) proportions with yellow fever neutralising antibody titre ≥8 four weeks after administration of yellow fever vaccine. Participants and field staff will not be masked to group allocation while the measurement of laboratory endpoints will be masked. Approximately equal numbers of participants will be resident in each of 28 geographic clusters (14 clusters in alternative and standard schedule groups); 784 enrolled for acquisition measurements and 336 for immunogenicity measurements.

DISCUSSION

Analysis will account for potential non-independence of measurements by cluster and so interpretation of effects will be at the individual level (i.e. a population of individuals). PVS-AcqImm will evaluate whether acquisition of vaccine-type pneumococci is reduced by the alternative compared to the standard schedule, which is required if the alternative schedule is to be effective. Likewise, evidence of superior immune response at 18 months of age and safety of PCV co-administration with yellow fever vaccine will support decision-making regarding the use of the alternative 1+1 schedule. Acquisition and immunogenicity outcomes will be essential for the interpretation of the results of the large field trial comparing the two schedules.

TRIAL REGISTRATION

International Standard Randomised Controlled Trial Number 72821613 .

Pneumococcal Immunization Strategies for High-Risk Pediatric Populations Worldwide: One Size Does Not Fit All

Despite the significant reduction in pneumococcal disease due to pneumococcal vaccines, protection of vulnerable high-risk individuals, especially pediatric populations, remains a great challenge. In an effort to maximize the protection of high-risk children against pneumococcal disease, a combined schedule that includes both conjugate and polysaccharide vaccines is recommended by several countries in the developed world. On the other hand, middle- and low-income countries do not have in place established policies for pneumococcal immunization of children at risk. Pneumococcal conjugate vaccines, despite their benefits, have several limitations, mainly associated with serotype replacement and the wide range of serotype coverage worldwide. In addition, PPV23-impaired immunogenicity and the hyporesponsiveness effect among populations at risk have been well-documented. Therefore, the added value of continuing to include PPV23 in vaccination schedules for high-risk individuals in the years to come remains to be determined by monitoring whether the replacing/remaining serotypes causing IPD are covered by PPV23 to determine whether its benefits outweigh its limitations. In this review, we aim to describe serotype distribution and vaccine efficacy data on pneumococcal disease in the pre- and post-PCV implementation era among high-risk children in both developed and developing countries, assessing the optimization of current recommendations for their vaccination against pneumococcal disease.

Estimating the risk of recurrent invasive pneumococcal disease in Australia, 1991-2016

BACKGROUND

Individuals who experience an initial episode of invasive pneumococcal disease (IPD) are at increased risk of recurrent episodes. However, the magnitude of risk has not been well-quantified in the pneumococcal conjugate vaccine era. Individuals with a previous episode of IPD are not commonly identified as a high-risk group in vaccination guidelines.

METHODS

Australian residents with at least one case of IPD between 1991 and 2016 were identified using routine public health surveillance data which included identified IPD risk factors. Incidence of recurrent IPD was calculated from 2001 onwards (after IPD became nationally notifiable) using time-to-event analyses with individuals contributing person-time at risk of recurrence if they survived greater than 14 days after initial episode onset.

RESULTS

From 1991 to 2016 there were 28,809 IPD episodes in 28,218 individuals. A total of 512 (1.8%) persons experienced 591 recurrent episodes. From 2001 to 2016 the incidence of recurrent IPD was 216.2 per 100,000 person-years, 27 times greater than the population rate of primary IPD during this period (8.0 per 100,000 population per year). Between 2011 and 2016, more than one-quarter of individuals experiencing recurrence had no IPD risk factors identified at first episode.

CONCLUSIONS

There is substantially increased risk of recurrent IPD after an initial episode. At least one-quarter of those with recurrent episodes have no identified risk factors at the initial episode. Given the potential preventability of future episodes, those with a previous IPD episode should be identified as a high-risk group and receive pneumococcal vaccination.

Paediatric pneumonia in high-income countries: Defining and recognising cases at increased risk of severe disease

World Health Organisation definitions of pneumonia severity are routinely used in research. In high income health care settings with high rates of pneumococcal vaccination and low rates of mortality, malnutrition and HIV infection, these definitions are less applicable. National guidelines from leading thoracic and infectious disease societies describe 'severe pneumonia' according to criteria derived from expert consensus rather than a robust evidence base. Contemporary cohort studies have used clinical outcomes such as intensive care therapy or invasive procedures for complicated pneumonia, to define severe disease. Describing severe pneumonia in such clinically relevant terms facilitates the identification of risk factors associated with worsened disease and the subsequently increased morbidity, and need for tertiary level care. The early recognition of children at higher risk of severe pneumonia informs site of care decisions, antibiotic treatment decisions as well as guiding appropriate investigations. Younger age, malnutrition, comorbidities, tachypnoea, and hypoxia have been identified as important associations with 'severe pneumonia' by WHO definition. Most studies have been performed in low-middle income countries and whilst they provide some insight into those at risk of mortality or treatment failure, their generalisability to the high-income setting is limited. There is a need to determine more precise definitions and criteria for severe disease in well-resourced settings and to validate factors associated with intensive care admission or invasive procedures to enhance the early recognition of those at risk.

Levels of pneumococcal conjugate vaccine coverage and indirect protection against invasive pneumococcal disease and pneumonia hospitalisations in Australia: An observational study

BACKGROUND

There is limited empiric evidence on the coverage of pneumococcal conjugate vaccines (PCVs) required to generate substantial indirect protection. We investigate the association between population PCV coverage and indirect protection against invasive pneumococcal disease (IPD) and pneumonia hospitalisations among undervaccinated Australian children.

METHODS AND FINDINGS

Birth and vaccination records, IPD notifications, and hospitalisations were individually linked for children aged <5 years, born between 2001 and 2012 in 2 Australian states (New South Wales and Western Australia; 1.37 million children). Using Poisson regression models, we examined the association between PCV coverage, in small geographical units, and the incidence of (1) 7-valent PCV (PCV7)-type IPD; (2) all-cause pneumonia; and (3) pneumococcal and lobar pneumonia hospitalisation in undervaccinated children. Undervaccinated children received <2 doses of PCV at <12 months of age and no doses at ≥12 months of age. Potential confounding variables were selected for adjustment a priori with the assistance of a directed acyclic graph. There were strong inverse associations between PCV coverage and the incidence of PCV7-type IPD (adjusted incidence rate ratio [aIRR] 0.967, 95% confidence interval [CI] 0.958 to 0.975, p-value < 0.001), and pneumonia hospitalisations (all-cause pneumonia: aIRR 0.991 95% CI 0.990 to 0.994, p-value < 0.001) among undervaccinated children. Subgroup analyses for children <4 months old, urban, rural, and Indigenous populations showed similar trends, although effects were smaller for rural and Indigenous populations. Approximately 50% coverage of PCV7 among children <5 years of age was estimated to prevent up to 72.5% (95% CI 51.6 to 84.4) of PCV7-type IPD among undervaccinated children, while 90% coverage was estimated to prevent 95.2% (95% CI 89.4 to 97.8). The main limitations of this study include the potential for differential loss to follow-up, geographical misclassification of children (based on residential address at birth only), and unmeasured confounders.

CONCLUSIONS

In this study, we observed substantial indirect protection at lower levels of PCV coverage than previously described-challenging assumptions that high levels of PCV coverage (i.e., greater than 90%) are required. Understanding the association between PCV coverage and indirect protection is a priority since the control of vaccine-type pneumococcal disease is a prerequisite for reducing the number of PCV doses (from 3 to 2). Reduced dose schedules have the potential to substantially reduce program costs while maintaining vaccine impact.

Impact of the introduction of pneumococcal conjugate vaccination on invasive pneumococcal disease and pneumonia in The Gambia: 10 years of population-based surveillance

Background

The Gambia introduced seven-valent pneumococcal conjugate vaccine (PCV7) in August 2009, followed by PCV13 in May, 2011, using a schedule of three primary doses without a booster dose or catch-up immunisation. We aimed to assess the long-term impact of PCV on disease incidence.

Methods

We did 10 years of population-based surveillance for invasive pneumococcal disease (IPD) and WHO defined radiological pneumonia with consolidation in rural Gambia. The surveillance population included all Basse Health and Demographic Surveillance System residents aged 2 months or older. Nurses screened all outpatients and inpatients at all health facilities using standardised criteria for referral. Clinicians then applied criteria for patient investigation. We defined IPD as a compatible illness with isolation of Streptococcus pneumoniae from a normally sterile site (cerebrospinal fluid, blood, or pleural fluid). We compared disease incidence between baseline (May 12, 2008–May 11, 2010) and post-vaccine years (2016–2017), in children aged 2 months to 14 years, adjusting for changes in case ascertainment over time.

Findings

We identified 22 728 patients for investigation and detected 342 cases of IPD and 2623 cases of radiological pneumonia. Among children aged 2–59 months, IPD incidence declined from 184 cases per 100 000 person-years to 38 cases per 100 000 person-years, an 80% reduction (95% CI 69–87). Non-pneumococcal bacteraemia incidence did not change significantly over time (incidence rate ratio 0·88; 95% CI, 0·64–1·21). We detected zero cases of vaccine-type IPD in the 2–11 month age group in 2016–17. Incidence of radiological pneumonia decreased by 33% (95% CI 24–40), from 10·5 to 7·0 per 1000 person-years in the 2–59 month age group, while pneumonia hospitalisations declined by 27% (95% CI 22–31). In the 5–14 year age group, IPD incidence declined by 69% (95% CI −28 to 91) and radiological pneumonia by 27% (95% CI −5 to 49).

Interpretation

Routine introduction of PCV13 substantially reduced the incidence of childhood IPD and pneumonia in rural Gambia, including elimination of vaccine-type IPD in infants. Other low-income countries can expect substantial impact from the introduction of PCV13 using a schedule of three primary doses.

Funding

Gavi, The Vaccine Alliance; Bill & Melinda Gates Foundation; UK Medical Research Council; Pfizer Ltd.

Streptococcus Pneumoniae septic arthritis in adults in Bristol and Bath, United Kingdom, 2006-2018: a 13-year retrospective observational cohort study

Few studies on adult pneumococcal septic arthritis are sufficiently large enough to assess both epidemiological trends following routine pneumococcal immunization and clinical disease. With major shifts in serotypes causing invasive pneumococcal disease (IPD), we wanted to determine the clinical phenotype of adult septic arthritis caused by Streptococcus pneumoniae. We conducted a retrospective cohort study of pneumococcal infections in Bristol and Bath, UK, 2006–2018. We defined pneumococcal septic arthritis as adults with clinically-confirmed septic arthritis, with pneumococcus isolated from sterile-site culture or urinary antigen test positivity. Clinical records were reviewed for each patient in the cohort. Septic arthritis accounted for 1.7% of all IPD cases. 45 cases of adult pneumococcal septic arthritis occurred, with disease typically affecting older adults and those with underlying comorbidity. 67% patients had another focus of infection during their illness. 66% patients required increased care on discharge and 43% had reduced range of movement. In-hospital case fatality rate was 6.7%. One-year patient mortality was 31%. Currently most cases of adult pneumococcal septic arthritis are due to non-PCV13 serotypes which are associated with more severe disease. Non-PCV-13 serotypes had higher prevalence of concomitant pneumococcal infection at another site (73.7% versus 36.6%), increased intensive care or high-dependency unit requirement (32.4% versus 0%), and increased inpatient and 1-year case fatality rate (8.8% versus 0%, and 32.4% versus 27.4% respectively) compared to PCV-13 serotypes. Pneumococcal septic arthritis remains a small proportion of IPD. However, there is significant associated morbidity and mortality, and pneumococcal septic arthritis requires monitoring in coming years.

A pragmatic health centre-based evaluation comparing the effectiveness of a PCV13 schedule change from 3+0 to 2+1 in a high pneumococcal carriage and disease burden setting in Malawi: a study protocol

INTRODUCTION

Streptococcus pneumoniae (the pneumococcus) is commonly carried as a commensal bacterium in the nasopharynx but can cause life-threatening disease. Transmission occurs by human respiratory droplets and interruption of this process provides herd immunity. A 2017 WHO Consultation on Optimisation of pneumococcal conjugate vaccines (PCV) Impact highlighted a substantial research gap in investigating why the impact of PCV vaccines in low-income countries has been lower than expected. Malawi introduced the 13-valent PCV (PCV13) into the national Expanded Programme of Immunisations in 2011, using a 3+0 (3 primary +0 booster doses) schedule. With evidence of greater impact of a 2+1 (2 primary +1 booster dose) schedule in other settings, including South Africa, Malawi's National Immunisations Technical Advisory Group is seeking evidence of adequate superiority of a 2+1 schedule to inform vaccine policy.

METHODS

A pragmatic health centre-based evaluation comparing impact of a PCV13 schedule change from 3+0 to 2+1 in Blantyre district, Malawi. Twenty government health centres will be randomly selected, with ten implementing a 2+1 and 10 to continue with the 3+0 schedule. Health centres implementing 3+0 will serve as the direct comparator in evaluating 2+1 providing superior direct and indirect protection against pneumococcal carriage. Pneumococcal carriage surveys will evaluate carriage prevalence among children 15-24 months, randomised at household level, and schoolgoers 5-10 years of age, randomly selected from school registers. Carriage surveys will be conducted 18 and 33 months following 2+1 implementation.

ANALYSIS

The primary endpoint is powered to detect an effect size of 50% reduction in vaccine serotype (VT) carriage among vaccinated children 15-24 months old, expecting a 14% and 7% VT carriage prevalence in the 3+0 and 2+1 arms, respectively.

ETHICS AND DISSEMINATION

The study has been approved by the Malawi College of Medicine Research Ethics Committee (COMREC; Ref: P05.19.2680), the University College London Research Ethics Committee (Ref: 8603.002) and the University of Liverpool Research Ethics Committee (Ref: 5439). The results from this study will be actively disseminated through manuscript publications and conference presentations.

TRIAL REGISTRATION NUMBER

NCT04078997.

Characteristics of Invasive Pneumococcal Disease Caused by Emerging Serotypes After the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine in England: A Prospective Observational Cohort Study, 2014-2018

BACKGROUND

England is experiencing a rapid increase in invasive pneumococcal disease (IPD) caused by serotypes 8, 12F, and 9N; their clinical characteristics and outcomes have not been described.

METHODS

Public Health England conducts national IPD surveillance. Cases due to emerging serotypes were compared with those included in the 13-valent pneumococcal conjugate vaccine (PCV13) and the remaining non-PCV13 serotypes.

RESULTS

There were 21 592 IPD cases during 2014-15 to 2017-18, including 20 108 (93.1%) with serotyped isolates and 17 450 (86.8%) with completed questionnaires. PCV13 serotypes were responsible for 20.1% (n = 4033), while serotype 8 (3881/20 108 [19.3%]), 12F (2365/20 108 [11.8%]), and 9N (1 296/20 108 [6.4%]) were together responsible for 37.5% of cases. Invasive pneumonia was the most common presentation (11 424/16 346 [69.9%]) and, overall, 67.0% (n = 11 033) had an underlying comorbidity. The median age (interquartile range) at IPD due to serotypes 8 (59 [45-72] years) and 12F (56 [41-70] years) was lower than serotype 9N (67 [53-80] years), PCV13 serotypes (68 [52-81] years), and remaining non-PCV13 serotypes (70 [53-82] years). Serotype 9N IPD cases also had higher comorbidity prevalence (748/1087 [68.8%]) compared to serotype 8 (1901/3228 [58.9%]) or 12F (1042/1994 [52.3%]), and higher case fatality (212/1128 [18.8%]) compared to 8.6% (291/3365) or 10.0% (209/2086), respectively.

CONCLUSIONS

Serotypes 8 and 12F were more likely to cause IPD in younger, healthier individuals and less likely to be fatal, while serotype 9N affected older adults with comorbidities and had higher case fatality.

Vaccination with LytA, LytC, or Pce of Streptococcus pneumoniae Protects against Sepsis by Inducing IgGs That Activate the Complement System

The emergence of non-vaccine serotypes of Streptococcus pneumoniae after the use of vaccines based in capsular polysaccharides demonstrates the need of a broader protection vaccine based in protein antigens and widely conserved. In this study, we characterized three important virulence factors of S. pneumoniae namely LytA, LytC, and Pce as vaccine candidates. These proteins are choline-binding proteins that belong to the cell wall hydrolases’ family. Immunization of mice with LytA, LytC, or Pce induced high titers of immunoglobulins G (IgGs) of different subclasses, with IgG1, IgG2a, and IgG2b as the predominant immunoglobulins raised. These antibodies activated the classical pathway of the complement system by increasing the recognition of C1q on the surface of pneumococcal strains of different serotypes. Consequently, the key complement component C3 recognized more efficiently these strains in the presence of specific antibodies elicited by these proteins, activating, therefore, the phagocytosis. Finally, a mouse sepsis model of infection was established, confirming that vaccination with these proteins controlled bacterial replication in the bloodstream, increasing the survival rate. Overall, these results demonstrate that LytA, LytC, and Pce can be protein antigens to be contained in a future universal vaccine against S. pneumoniae.

Retrospective Impact Analysis and Cost-Effectiveness of the Pneumococcal Conjugate Vaccine Infant Program in Australia

Australia introduced the 7-valent pneumococcal conjugate vaccine (7vPCV) on the universal infant National Immunisation Program (NIP) in 2005 and replaced it with the 13-valent pneumococcal conjugate vaccine (13vPCV) in 2011, both under a 3 + 0 schedule. The objective of this analysis was to quantify the clinical and economic impact of the universal infant PCV program in Australia from its introduction. A decision-analytic model was developed to estimate the historical impact of pneumococcal conjugate vaccine (PCV) programs in Australia from a direct health care perspective. Historical incidence of invasive pneumococcal disease (IPD), pneumonia, and otitis media (OM) were obtained from available Australian epidemiologic databases supplemented with published data. Costs were from Medicare Benefits Schedule in 2018 Australian dollars and utility weights from published sources. Historical observed changes in disease for the universal PCV NIP era (2005–2017) were compared against a “no-vaccine” scenario. The expected incidence for the no-vaccine scenario in years 2005–2017 was calculated using pre-universal PCV NIP era (2001–2004) data. Averted cases, deaths, incremental costs, and quality-adjusted life years (QALYs) were obtained by subtracting the vaccine scenario totals from the no-vaccine scenario totals. From the inclusion in the universal infant NIP, 7vPCV and 13vPCV are estimated to have prevented 1,770,024 cases of pneumococcal disease (IPD = 16,392; OM = 1,575,491; pneumonia = 102,059) and 1195 associated deaths. Over this period, there was a total 24,335 QALYs gained. Costs for the universal infant NIP were offset by $733 million direct costs saved, resulting in an incremental cost-effectiveness ratio of $3347 per QALY gained. PCVs have provided substantial public health and economic value from sustained use in Australia. Results are conservative, since long-term pneumococcal disease consequences and broader socioeconomic benefits were not considered. Maintaining 13vPCV on the Australian infant NIP under the newly implemented 2 + 1 schedule will likely provide more return on investment and sustained reductions in pneumococcal disease.

Assessing the impact of the 13 valent pneumococcal vaccine on childhood empyema in Australia

BACKGROUND

Empyema is a serious complication of pneumonia frequently caused by Streptococcus pneumoniae (SP). We assessed the impact of the 13-valent pneumococcal conjugate vaccine (13vPCV) on childhood pneumonia and empyema after inclusion in the Australian National Immunisation Program.

METHODS

For bacterial pneumonia and empyema hospitalisations, we ascertained incidence rates (IRs) using the National Hospital Morbidity Database International Statistical Classification of Disease discharge codes and relevant population denominators, and calculated incidence rate ratios (IRR) comparing the 13vPCV period (June 2012-May 2017) with the 7vPCV period (June 2007-May 2011). Blood and pleural fluid (PF) cultures and PF PCR of 401 children with empyema from 11 Australian hospitals during the 13vPCV period were compared with our previous study in the 7vPCV period.

FINDINGS

Across 7vPCV and 13vPCV periods, IRs per million children (95% CIs) were 1605 (1588 to 1621) and 1272 (1259 to 1285) for bacterial pneumonia, and 14.23 (12.67 to 15.79) and 17.89 (16.37 to 19.42) for empyema hospitalisations. IRRs were 0.79 (0.78 to 0.80) for bacterial pneumonia and 1.25 (1.09 to 1.44) for empyema. Of 161 empyema cases with SP serotypes, 147 (91.3%) were vaccine types. ST3 accounted for 76.4% of identified serotypes in the 13vPCV period, more than double than the 7vPCV period (p<0.001); ST19A decreased from 36.4% to 12.4%. No cases of ST1 empyema were identified in the 13vPCV period versus 14.5% in the 7vPCV period.

INTERPRETATION

13vPCV resulted in a significant reduction in all-cause hospitalisations for bacterial pneumonia but empyema hospitalisations significantly increased, with emergence of pneumococcal ST3 as the dominant serotype in empyema.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trial Registry ACTRN 12614000354684.

Long-term Impact of Pneumococcal Conjugate Vaccines on Invasive Disease and Pneumonia Hospitalizations in Indigenous and Non-Indigenous Australians

BACKGROUND

Universal pneumococcal conjugate vaccine (PCV) programs began in Indigenous Australian children in 2001 and all children in 2005, changing to 13-valent PCV (PCV13) in 2011. We used laboratory data for invasive pneumococcal disease (IPD) and coded hospitalizations for noninvasive pneumococcal community-acquired pneumonia (PnCAP) to evaluate long-term impact.

METHODS

Annual incidence (per 100 000 population) was calculated for age-specific total IPD, PCV13 non-7-valent PCV (PCV7) serotypes, and PnCAP by Indigenous status. Incidence in the pre-universal PCV7 (2002-2004), early PCV7 (2005-2007), pre-PCV13 (2008 to mid-2011), and post-PCV13 (mid-2011 to 2016) periods was used to calculate incidence rate ratios (IRRs).

RESULTS

In the total population, all-age incidence of IPD declined from 11.8 pre-PCV7 to 7.1 post-PCV13 (IRR, 0.61 [95% confidence interval {CI}, .59-.63]) but for PnCAP declined among ages <1 year (IRR, 0.34 [95% CI, .25-.45]) and 1-4 years (IRR, 0.50 [95% CI, .43-.57]) but increased significantly among age ≥5 years (IRRs, 1.08-1.14). In Indigenous people, baseline PCV13 non-PCV7 IPD incidence was 3-fold higher, amplified by a serotype 1 epidemic in 2011. By 2015-2016, although incidence of IPD and PnCAP in children aged <5 years decreased by 38%, neither decreased in people aged ≥5 years.

CONCLUSIONS

Fifteen years post-PCV and 5 years post-PCV13, direct and indirect impact on IPD and PnCAP differed by age and between Indigenous and non-Indigenous people, with potential implications for long-term PCV impact in comparable settings.Fifteen years after pneumococcal conjugate vaccine (PCV) introduction and 5 years post-PCV13, direct and indirect impact on invasive pneumococcal disease and pneumococcal community-acquired pneumonia differed by age and between Indigenous and non-Indigenous people, with potential implications for long-term PCV impact in comparable settings.

A Rationale for Change: An Increase in Invasive Pneumococcal Disease in Fully Vaccinated Children

Increasing numbers of cases of invasive pneumococcal disease in fully vaccinated children have occurred in Australia since 2013. A review of cases informed a change from a "3 + 0" infant schedule (13-valent pneumococcal conjugate vaccine at 2, 4, and 6 months) to a "2 + 1" schedule (2, 4, and 12 months).

Early Impact of 13-Valent Pneumococcal Conjugate Vaccine Use on Invasive Pneumococcal Disease Among Adults With and Without Underlying Medical Conditions-United States

BACKGROUND

The 13-valent pneumococcal vaccine (PCV13) was introduced for US children in 2010 and for immunocompromised adults ≥19 years old in series with the 23-valent polysaccharide vaccine (PPSV23) in 2012. We evaluated PCV13 indirect effects on invasive pneumococcal disease (IPD) among adults with and without PCV13 indications.

METHODS

Using Active Bacterial Core surveillance and the National Health Survey, using Active Bacterial Core surveillance and the National Health Interview Survey, we estimated and compared IPD incidence in 2013-2014 and 2007-2008, by age and serotype group (PCV13, PPSV23-unique, or nonvaccine types [NVTs]), among adults with and without PCV13 indications.

RESULTS

IPD incidence declined among all adults. Among adults 19-64 years, PCV13-type IPD declined 57% (95% confidence interval [CI], -68% to -43%) in adults with immunocompromising conditions (indication for PCV13 use), 57% (95% CI, -62% to -52%) in immunocompetent adults with chronic medical conditions (CMCs, indications for PPSV23 use alone), and 74% (95% CI, -78% to -70%) in adults with neither vaccine indication. Among adults aged ≥65 years, PCV13-type IPD decreased 68% (95% CI, -76% to -60%) in those with immunocompromising conditions, 68% (95% CI, -72% to -63%) in those with CMCs, and 71% (95% CI, -77% to -64%) in healthy adults. PPSV23-unique types increased in adults 19‒64 years with CMCs, and NVTs did not change among adults with or without PCV13 indications. From 2013 to 2014, non-PCV13 serotypes accounted for 80% of IPD.

CONCLUSIONS

IPD incidence among US adults declined after PCV13 introduction in children. Similar reductions in PCV13-type IPD in those with and without PCV13 indications suggest that observed benefits are largely due to indirect effects from pediatric PCV13 use rather than direct use among adults.

The impact of the changing pneumococcal national immunisation program among older Australians

Australia has a universal infant pneumococcal conjugate vaccination program and until recently a universal pneumococcal polysaccharide vaccine program for non-Indigenous adults aged ≥65 years and Indigenous adults aged ≥50 years. We documented the impacts of infant and adult vaccination programs on the epidemiology of invasive pneumococcal disease (IPD) in Indigenous and non-Indigenous adults. IPD notifications from the National Notifiable Disease Surveillance System were analysed from 2002 to 2017, grouped by age, vaccine serotype group and Indigenous status. Since the universal funding of infant and elderly pneumococcal vaccination programs in January 2005, total IPD decreased by 19% in non-Indigenous adults aged ≥65 years but doubled in Indigenous adults aged ≥50 years. Vaccine uptake was suboptimal in both groups but lower in Indigenous adults. IPD due to the serotypes contained in the pneumococcal conjugate vaccines (PCV) except for serotype 3 declined markedly over the study period but were replaced by non-PCV serotypes. Serotype 3 is currently the most common in older adults. In the populations eligible for the adult 23-valent pneumococcal polysaccharide vaccine (23vPPV) program, IPD rates due to its exclusive serotypes increased to a lower extent than non-vaccine types. In 2017, non-vaccine serotypes accounted for most IPD in the older population eligible for the 23vPPV program, while it's eleven exclusive serotypes accounted for the majority of IPD in younger adults. Infant and adult pneumococcal vaccination programs in Australia have shaped the serotype-specific epidemiology of IPD in older adults. IPD remains a significant health burden for the Indigenous population. Herd immunity impact is clear for PCV serotypes excluding serotype 3 and serotype replacement is evident for non-PCV serotypes. The adult 23vPPV immunisation program appears to have partially curbed replacement with IPD due to its eleven exclusive serotypes, highlighting a potential benefit of increasing adult 23vPPV coverage in Australia.

Vaccine strategies to reduce the burden of pneumococcal disease in HIV-infected adults in Africa

INTRODUCTION

Streptococcus pneumoniae is the leading cause of invasive bacterial disease, globally. Despite antiretroviral therapy, adults infected with human immunodeficiency virus (HIV) are also at high risk of pneumococcal carriage and disease. Pneumococcal conjugate vaccines (PCVs) provide effective protection against vaccine serotype (VT) carriage and disease in children, and have been introduced worldwide, including most HIV-affected low- and middle-income countries. Unlike high-income countries, the circulation of VT persists in the PCV era in some low-income countries and results in a continued high burden of pneumococcal disease in HIV-infected adults. Moreover, no routine vaccination that directly protects HIV-infected adults in such settings has been implemented.

AREAS COVERED

Nonsystematic review on the pneumococcal burden in HIV-infected adults and vaccine strategies to reduce this burden.

EXPERT OPINION

We propose and discuss the relative merit of changing the infant PCV program to use (1a) a two prime plus booster dose schedule, (1b) a two prime plus booster dose schedule with an additional booster dose at school entry, to directly vaccinate (2a) HIV-infected adults or vaccinating (2b) HIV-infected pregnant women for direct protection, with added indirect protection to the high-risk neonates. We identify key knowledge gaps for such an evaluation and propose strategies to overcome them.

Trends in Bacteremia Over 2 Decades in the Top End of the Northern Territory of Australia

Background

Information on the local distribution of bloodstream pathogens helps to guide empiric antibiotic selection and can generate hypotheses regarding the effectiveness of infection prevention practices. We assessed trends in bacterial blood culture isolates at Royal Darwin Hospital (RDH) in the Northern Territory of Australia between 1999 and 2019.

Methods

 Species identification was extracted for all blood cultures first registered at RDH. Thirteen organisms were selected for focused analysis. Trends were examined graphically and using univariable linear regression.

Results

 Between 1999 and 2019, 189 577 blood cultures from 65 276 patients were processed at RDH. Overall, 6.72% (12 747/189 577) of blood cultures contained a bacterial pathogen. Staphylococcus aureus was the most common cause of bacteremia during the first decade, with an estimated incidence of 96.6 episodes per 100 000 person-years (py; 95% CI, 72.2-121/100 000 py) in 1999. Since 2009, S. aureus bacteremia has declined markedly, whereas there has been an inexorable rise in Escherichia coli bacteremia (30.1 to 74.7/100 000 py between 1999 and 2019; P < .001), particularly in older adults. Since 2017, E. coli has been more common than S. aureus. Rates of Streptococcus pneumoniae bacteremia have reduced dramatically in children, while Burkholderia pseudomallei remained the fourth most common bloodstream isolate overall.

Conclusions

 The incidence of S. aureus bacteremia, though high by international standards, is declining at RDH, possibly in part due to a sustained focus on both community and hospital infection prevention practices. Gram-negative bacteremia, particularly due to E. coli, is becoming more common, and the trend will likely continue given our aging population.

Incidence of invasive pneumococcal disease after introduction of the 13-valent conjugate pneumococcal vaccine in British Columbia: A retrospective cohort study

BACKGROUND

A significant reduction in invasive pneumococcal disease (IPD) has been reported, across all ages, following the implementation of 7-valent conjugate pneumococcal vaccine (PCV7) globally, as part of infant immunization programs. We explored the additional impact of PCV13 on IPD over a 14-year period.

METHODS

Using provincial laboratory surveillance and hospitalization data (N = 5791), we calculated the annual incidence of IPD following the implementation of PCV13 vaccine. Poisson regression was used to evaluate changes in the overall incidence of IPD, and serotype-specific IPD between PCV7 (2004-10) and PCV13 (2011-2015) eras.

RESULTS

Overall, IPD rates have seen a modest decline in the PCV13 compared to the PCV7 era (IRR 0.84; 95% CI: 0.79-0.89); this was seen in children ≤2 years of age, and the majority of the adult cohort. Rates of vaccine-type IPD (PCV7 and PCV13) also decreased in the PCV13 era. In contrast, IPD incidence related to non-PCV13 (IRR: 1.56; 95%CI:1.43-1.72) and non-vaccine serotypes (IRR: 2.12; 95%CI:1.84-2.45) increased in the PCV13 era compared to the PCV7 era.

CONCLUSIONS

A modest reduction in IPD from the PCV13 vaccine was observed, with gains limited to the immunized cohort and adults. However, a significant increase in non-vaccine serotypes emphasizes the need for continued surveillance.

Nationwide Trends of Invasive Pneumococcal Disease in Spain From 2009 Through 2019 in Children and Adults During the Pneumococcal Conjugate Vaccine Era

Background

Introduction of pneumococcal conjugate vaccines (PCVs) has reduced the disease caused by vaccine serotypes in children, providing herd protection to adults. However, the emergence of nonvaccine serotypes is of great concern worldwide.

Methods

This study includes national laboratory data from invasive pneumococcal disease (IPD) cases that affected pediatric and adult populations during 2009–2019. The impact of implementing different vaccine strategies for immunocompetent adults by comparing Spanish regions that used the 13-valent PCV (PCV13) vs regions that used the 23-valent pneumococcal polysaccharide vaccine (PPV23) was also analyzed for 2017−2019.

Results

The overall reductions in IPD cases by PCV13 serotypes in children and adults were 88% and 59%, respectively, during 2009–2019, with a constant increase in serotype 8 in adults since 2015. IPD cases by additional serotypes covered by PPV23 increased from 20% in 2009 to 52% in 2019. In children, serotype 24F was the most frequent in 2019, whereas serotypes 3 and 8 accounted for 36% of IPD cases in adults. Introduction of PCV13 or PPV23 in the adult calendar of certain Spanish regions reduced the IPD cases by PCV13 serotypes by up to 25% and 11%, respectively, showing a decrease of serotype 3 when PCV13 was used.

Conclusions

Use of PCV13 in children has affected the epidemiology, reducing the burden of IPD in children but also in adults by herd protection; however, the increase in serotype 8 in adults is worrisome. Vaccination with PCV13 in adults seems to control IPD cases by PCV13 serotypes including serotype 3.

Paediatric empyema: worsening disease severity and challenges identifying patients at increased risk of repeat intervention

OBJECTIVE

Empyema is the most common complication of pneumonia. Primary interventions include chest drainage and fibrinolytic therapy (CDF) or video-assisted thoracoscopic surgery (VATS). We describe disease trends, clinical outcomes and factors associated with reintervention.

DESIGN/SETTING/PATIENTS

Retrospective cohort of paediatric empyema cases requiring drainage or surgical intervention, 2011-2018, admitted to a large Australian tertiary children's hospital.

RESULTS

During the study, the incidence of empyema increased from 1.7/1000 to 7.1/1000 admissions (p<0.001). We describe 192 cases (174 CDF and 18 VATS), median age 3.0 years (IQR 1-5), mean fever duration prior to intervention 6.2 days (SD ±3.3 days) and 50 (26%) cases admitted to PICU. PICU admission increased during the study from 18% to 34% (p<0.001). Bacteraemia occurred in 23/192 (12%) cases. A pathogen was detected in 131/192 (68%); Streptococcus pneumoniae 75/192 (39%), S. aureus 25/192 (13%) and group A streptococcus 13/192 (7%). Reintervention occurred in 49/174 (28%) and 1/18 (6%) following primary CDF and VATS. Comparing repeat intervention with single intervention cases, a continued fever postintervention increased the likelihood for a repeat intervention (OR 1.3 per day febrile; 95% CI 1.2 to 1.4, p<0.0001). Younger age, prolonged fever preintervention and previous antibiotic treatment were not associated with initial treatment failure (all p>0.05).

CONCLUSION

We report increasing incidence and severity of empyema in a large tertiary hospital. One in four patients required a repeat intervention after CDF. Neither clinical variables at presentation nor early investigations were able to predict initial treatment failure.

Meningitis vaccines in children: what have we achieved and where next?

PURPOSE OF REVIEW

This review highlights the recent impacts of vaccines against the major bacterial causes of meningitis in children, and the challenges for further prevention of bacterial meningitis, with a focus on Streptococcus pneumoniae, Neisseria meningitidis and group B Streptococcus.

RECENT FINDINGS

Conjugate vaccines against S. pneumoniae and N. meningitidis have resulted in dramatic reductions in bacterial meningitis globally where they have been used. Recent licensure and use of capsular group B meningococcal protein vaccines have further reduced meningococcal meningitis in infants, young children and adolescents for countries with endemic disease and during outbreaks.

SUMMARY

Existing vaccines to prevent bacterial meningitis in children should be utilized in countries with significant numbers of cases of pneumococcal and/or meningococcal meningitis. Vaccines, which are able to protect against more than 13 serotypes of S. pneumoniae are in clinical trials and should be able to further reduce pneumococcal meningitis cases. Cost effective meningococcal vaccines against non-A capsular groups are needed for low-resource countries. There remains an urgent need for a vaccine against group B Streptococcus, which is a major cause of neonatal meningitis globally and for which no vaccine currently exists.

10-Valent pneumococcal non-typeable H. influenzae protein D conjugate vaccine (PHiD-CV10) versus 13-valent pneumococcal conjugate vaccine (PCV13) as a booster dose to broaden and strengthen protection from otitis media (PREVIX_BOOST) in Australian Aboriginal children: study protocol for a randomised controlled trial

INTRODUCTION

Streptococcus pneumoniae and non-typeable Haemophilus influenzae (NTHi) are major otitis media pathogens that densely co-colonise the nasopharynx and infect the middle ear of Australian Aboriginal infants from very early in life. Our co-primary hypotheses are that at 18 months of age infants receiving 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) compared with those receiving 13-valent pneumococcal conjugate vaccine (PCV13) as a booster at 12 months of age will have higher antibody levels to Haemophilus influenzae protein D and that infants receiving PCV13 will have higher antibody levels to PCV13-only serotypes 3, 6A and 19A.

METHODS AND ANALYSES

Our randomised controlled trial will enrol 270 Aboriginal children at 12 months of age to a booster dose of either PHiD-CV10 or PCV13. Children who completed the three-dose primary course schedules of PHiD-CV10 at 2, 4, 6 months of age; PCV13 at 2, 4, 6 months of age; or a combination schedule of PHiD-CV10 at 1, 2, 4 months of age plus PCV13 at 6 months of age are eligible. The co-primary assessor-blinded outcomes when the infants are 18 months of age are as follows: (a) IgG geometric mean concentration (GMC) and proportion with IgG ≥100 EU/mL for protein D, and (b) IgG GMC and the proportion with IgG ≥0.35 µg/mL for pneumococcal serotypes 3, 6A and 19A. Secondary immunogenicity comparisons of six primary and booster dose schedules of 10 shared serotypes at 18 months of age, nasopharyngeal carriage, all forms of otitis media, hearing loss and developmental milestones at 18, 24, 30 and 36 months of age will be reported.

ETHICS AND DISSEMINATION

Ethics committees of NT Department of Health, Menzies, WA Department of Health and WA Aboriginal Health approved the study. Results will be presented to communities, at conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT01735084.

High residual carriage of vaccine-serotype Streptococcus pneumoniae after introduction of pneumococcal conjugate vaccine in Malawi

There are concerns that pneumococcal conjugate vaccines (PCVs) in sub-Saharan Africa sub-optimally interrupt Streptococcus pneumoniae vaccine-serotype (VT) carriage and transmission. Here we assess PCV carriage using rolling, prospective nasopharyngeal carriage surveys between 2015 and 2018, 3.6–7.1 years after Malawi’s 2011 PCV13 introduction. Carriage decay rate is analysed using non-linear regression. Despite evidence of reduction in VT carriage over the study period, there is high persistent residual carriage. This includes among PCV-vaccinated children 3–5-year-old (16.1% relative reduction from 19.9% to 16.7%); PCV-unvaccinated children 6–8-year-old (40.5% reduction from 26.4% to 15.7%); HIV-infected adults 18-40-years-old on antiretroviral therapy (41.4% reduction from 15.2% to 8.9%). VT carriage prevalence half-life is similar among PCV-vaccinated and PCV-unvaccinated children (3.26 and 3.34 years, respectively). Compared with high-income settings, there is high residual VT carriage 3.6–7.1 years after PCV introduction. Rigorous evaluation of strategies to augment vaccine-induced control of carriage, including alternative schedules and catch-up campaigns, is required.

Impact of pneumococcal conjugate vaccines (PCV) in controlling carriage needs to be evaluated to inform vaccine policy. Here, Swarthout et al. show in a prospective rolling cross-sectional study in Malawi a high residual prevalence of vaccine-serotype S. pneumoniae 7 years after PCV introduction.

Impact of 10-Valent Pneumococcal Conjugate Vaccine Introduction on Pneumococcal Carriage and Antibiotic Susceptibility Patterns Among Children Aged <5 Years and Adults With Human Immunodeficiency Virus Infection: Kenya, 2009-2013

BACKGROUND

Kenya introduced 10-valent pneumococcal conjugate vaccine (PCV10) among children <1 year in 2011 with catch-up vaccination among children 1-4 years in some areas. We assessed changes in pneumococcal carriage and antibiotic susceptibility patterns in children <5 years and adults.

METHODS

During 2009-2013, we performed annual cross-sectional pneumococcal carriage surveys in 2 sites: Kibera (children <5 years) and Lwak (children <5 years, adults). Only Lwak had catch-up vaccination. Nasopharyngeal and oropharyngeal (adults only) swabs underwent culture for pneumococci; isolates were serotyped. Antibiotic susceptibility testing was performed on isolates from 2009 and 2013; penicillin nonsusceptible pneumococci (PNSP) was defined as penicillin-intermediate or -resistant. Changes in pneumococcal carriage by age (<1 year, 1-4 years, adults), site, and human immunodeficiency virus (HIV) status (adults only) were calculated using modified Poisson regression, with 2009-2010 as baseline.

RESULTS

We enrolled 2962 children (2073 in Kibera, 889 in Lwak) and 2590 adults (2028 HIV+, 562 HIV-). In 2013, PCV10-type carriage was 10.3% (Lwak) to 14.6% (Kibera) in children <1 year and 13.8% (Lwak) to 18.7% (Kibera) in children 1-4 years. This represents reductions of 60% and 63% among children <1 year and 52% and 60% among children 1-4 years in Kibera and Lwak, respectively. In adults, PCV10-type carriage decreased from 12.9% to 2.8% (HIV+) and from 11.8% to 0.7% (HIV-). Approximately 80% of isolates were PNSP, both in 2009 and 2013.

CONCLUSIONS

PCV10-type carriage declined in children <5 years and adults post-PCV10 introduction. However, PCV10-type and PNSP carriage persisted in children regardless of catch-up vaccination.

Increasing Rates of Pediatric Empyema and Disease Severity With Predominance of Serotype 3 S. pneumonia: An Australian Single-center, Retrospective Cohort 2011 to 2018

BACKGROUND

The impact of universal 13-valent pneumococcal conjugate vaccine immunization on pediatric empyema rates and pathogens in Australia is not known. We aimed to describe empyema epidemiology, clinical characteristics and treatment during an 8-year period.

METHODS

A retrospective study between 2011 and 2018 of empyema cases admitted to a large pediatric referral hospital, for management with either pleural drainage and fibrinolytics or surgical intervention.

RESULTS

There were 195 cases in 8 years. Empyema incidence and ICU admission rates significantly increased during the study with a peak incidence of 7.1/1000 medical admissions in 2016 (χ for trend of incidence 37.8, P < 0.001 and for ICU admissions 15.3, P < 0.001). S. pneumoniae was the most common pathogen (75/195, 39%) with serotype 3 the most detected (27/75: 27%). S. pyogenes compared with S. pneumoniae had significantly fewer days of fever before admission (3.9 vs. 6.4, mean difference 2.4, 95% CI: 0.84-4.08, P = 0.003) and higher proportion requiring direct ICU admission (6/75; 8% vs. 7/15; 47%, P < 0.001). Compared with S. pneumoniae, cases with no pathogen detected by culture or PCR had fewer days of fever post intervention (4.4 vs. 7.4 days, mean difference 2.7 days, P = 0.002). S. aureus occurred more commonly in infants (10/25; 40% vs. 1/75; 1%, P < 0.001) and children of indigenous background (5/25; 20% vs. 1/75; 1%, P < 0.001) compared with S. pneumoniae.

CONCLUSIONS

We report increasing rates of pediatric empyema with higher proportions requiring ICU treatment. The most common pathogens detected were S. pneumoniae, S. aureus and S. pyogenes. Despite high 13-valent pneumococcal conjugate vaccine coverage, serotype 3 was the most common S. pneumoniae serotype identified.

Effectiveness of 7- and 13-Valent Pneumococcal Conjugate Vaccines in a Schedule Without a Booster Dose: A 10-Year Observational Study

Background

Unique among high-income countries, Australia has used a 3 + 0 schedule (3 primary doses, no booster) for infant pneumococcal conjugate vaccine (PCV) since January 2005, initially 7 valent (PCV7) then 13 valent (PCV13) from July 2011. We measured vaccine effectiveness (VE) of both PCVs against invasive pneumococcal disease (IPD) using 2 methods.

Methods

Cases were IPD notifications to the national surveillance system of children eligible for respective PCVs. For case-control method, up to 10 age-matched controls were derived from the Australian Childhood Immunisation Register. For indirect cohort method, controls were IPD cases due to serotypes not in PCVs. VE was calculated as (1 - odds ratio [OR]) × 100 by logistic regression. VE waning was estimated as odds of vaccine type (VT) IPD in consecutive 12-month periods post-dose 3.

Results

Between 2005 and 2014, there were 1209 and 308 IPD cases in PCV7-eligible and PCV13-eligible cohorts, respectively. Both methods gave comparable VE estimates. In infants, VE for 3 doses against VT IPD was 92.9% (95% confidence interval [CI], 27.7% to 99.3%) for PCV7 and 86.5% (95% CI, 11.7% to 97.9%) for PCV13. From 12 months post-dose 3, the odds of VT IPD by 24-36 months increased significantly for PCV7 (5.6, 95% CI, 1.2-25.4) and PCV13 (5.9, 95% CI, 1.0-35.2).

Conclusions

For both PCVs in a 3 + 0 schedule, despite similar VE, progressive increase in breakthrough cases only occurred post-PCV13. This supports the importance of a booster dose of PCV13 in the second year of life to maintain protection.

Clinical Effectiveness of Conjugate Pneumococcal Vaccination in Hematopoietic Stem Cell Transplantation Recipients

Hematopoietic stem cell transplantation (HSCT) recipients are vulnerable to invasive pneumococcal disease (IPD), with reported IPD rates ranging from 3.81 to 22.5/1000 HSCT. This IPD risk could relate to immunodeficiency, low vaccination uptake, and poor immunogenicity of pneumococcal polysaccharide vaccine (PPV). Literature comparing the clinical effectiveness of pneumococcal conjugate vaccination (PCV) and PPV after HSCT is limited. In this retrospective analysis of HSCT recipients at our center from 2004 to 2015, we evaluated vaccination uptake and compared IPD rates in patients receiving PPV (pre-2010 group) and PCV (post-2010 group). IPD was determined from microbiological results for all HSCT recipients from January 2004 to June 30, 2019. Eight hundred patients had a total of 842 HSCT events, including autologous HSCT (auto-HSCT; n = 562) and allogeneic HSCT (allo-HSCT; n = 280). More than 90% of the HSCT recipients were enrolled, and >93% of surviving HSCT recipients completed the vaccination protocol. Fifteen IPD episodes occurred in 13 patients between 2004 and June 30, 2019. Thirteen episodes occurred in the pre-2010 group, even though 9 of 13 (69%) serotyped isolates were covered by PPV. Two episodes occurred in the post-2010 group; neither serotype was covered by PCV. Thus, with PCV introduction, IPD rate was significantly reduced from 38.5/1000 unique HSCTs pre-2010 to 4.0/1000 unique HSCTs post-2010 (P < .001). A significant reduction was seen in both auto-HSCTs (from 29.4 to 3.1 /1000 unique auto-HSCTs; P = .011) and allo-HSCTs (from 58.3 to 5.6/1000 unique allo-HSCTs; P = .011). PCV demonstrated superior clinical effectiveness over PPV, highlighting its importance in preventing infectious complications after HSCT. Robust vaccination programs at transplantation centers are needed to optimize vaccination uptake and completion.

Impact of pneumococcal conjugate vaccines introduction on antibiotic resistance of Streptococcus pneumoniae meningitis in children aged 5 years or younger, Israel, 2004 to 2016

Background

Empiric treatment of pneumococcal meningitis includes ceftriaxone with vancomycin to overcome ceftriaxone resistant disease. The addition of vancomycin bears a risk of adverse events, including increased antibiotic resistance. We assessed antibiotic resistance rates in pneumococcal meningitis before and after pneumococcal conjugate vaccine (PCV) implementation.

Methods

All pneumococcal meningitis episodes in children aged 5 years and younger, from 2004 to 2016, were extracted from the nationwide bacteremia and meningitis surveillance database. For comparison purposes, we defined pre-PCV period as 2004–2008 and PCV13 period as 2014–2016. Minimal inhibitory concentration (MIC) > 0.06 and > 0.5 μg/mL were defined as penicillin and ceftriaxone resistance, respectively.

Results

Overall, 325 episodes were identified. Pneumococcal meningitis incidence rates declined non-significantly by 17%, comparing PCV13 and pre-PCV periods. Throughout the study, 90% of isolates were tested for antibiotic susceptibility, with 26.6%, 2.1% and 0% of isolates resistant to penicillin, ceftriaxone and vancomycin, respectively. Mean proportions (± SD) of meningitis caused by penicillin-resistant pneumococci were 40.5% ± 8.0% and 9.6% ± 7.4% in the pre-PCV and the PCV13 periods, respectively, resulting in an overall 83.9% reduction (odd ratio:0.161; 95% confidence interval: 0.059–0.441) in penicillin resistance rates. The proportions of meningitis caused by ceftriaxone resistant pneumococci were 5.0% ± 0.8% in the pre-PCV period, but no ceftriaxone resistant isolates were identified since 2010.

Conclusions

PCV7/PCV13 sequential introduction resulted in > 80% reduction of penicillin- resistant pneumococcal meningitis and complete disappearance of ceftriaxone resistant disease. These trends should be considered by the treating physician when choosing an empiric treatment for pneumococcal meningitis.

Long-term Vaccine Impact on Invasive Pneumococcal Disease Among Children With Significant Comorbidities in a Large Australian Birth Cohort

BACKGROUND

Little is known about long-term invasive pneumococcal disease (IPD) incidence in children with risk factors (RFs) in populations with high coverage pneumococcal conjugate vaccine (PCV) programs. We measured IPD burden and changes with PCV use in children by RF status.

METHODS

A retrospective cohort of all live births in 2001-2012 in New South Wales, Australia was linked to IPD, hospitalization and death data. RFs were identified from International Classification of Diseases codes in linked hospitalizations. For each RF adjusted hazard ratios (aHRs, using Cox models), population attributable fractions (PAFs) and changes post-PCV relative to baseline for IPD were calculated.

RESULTS

One-thousand two-hundred fifty-one IPD cases occurred in ~1.1 million children in 12-year study cohort. The 75,404 children (6.8% of cohort) with RFs accounted for 255 (20.4%) IPD cases [rate (per 100,000 person-years) of 61 compared with 14 in no RFs]. Asthma was most common RF (n = 41,074; 3.6%) but highest IPD risk was in 2452 children (0.2%) with immunosuppression, splenic dysfunction or breach in cerebrospinal fluid barrier (aHR~20; PAF 0.7-1.8%) versus asthma (aHR 5.3; PAF 14.8%). Compared with 2001-2004 birth cohort (baseline), IPD incidence in PCV-eligible 2009-2012 birth cohort was 78% (95% confidence interval: -72% to -82%) less in children without RFs. IPD declined nonsignificantly (13%; 95% confidence interval: -70% to +138%) in highest IPD risk group, but by 67% (-43% to -82%) in children with other RFs.

CONCLUSIONS

By 8 years of universal PCV, IPD incidence reduced significantly in all children except in the 0.2% at highest risk, for whom antibiotic prophylaxis and additional vaccine doses are recommended but compliance and effectiveness remain uncertain.

Invasive Pneumococcal Disease in Children's Hospitals: 2014-2017

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed in the United States in 2010. We describe invasive pneumococcal disease (IPD) in children at 8 children's hospitals in the US from 2014 to 2017.

METHODS

Children with IPD occurring from 2014 to 2017 were identified from a prospective study. Demographic and clinical data, including results of any immune evaluation along with the number and dates of previous pneumococcal conjugate vaccines administered, were recorded on case report forms. Isolate serotypes were determined in a central laboratory. Pneumococcal conjugate vaccine doses were counted if IPD occurred ≥2 weeks after a dose.

RESULTS

PCV13 serotypes accounted for 23.9% (115 out of 482) of IPD isolates from 2014 to 2017. Serotypes 3, 19A, and 19F accounted for 91% of PCV13 serotypes. The most common non-PCV13 serotypes were 35B, 23B, 33F, and 22F. An underlying condition was significantly (P < .0001) more common in children with IPD due to non-PCV13 serotypes (200 out of 367, 54.5%) than for children with PCV13 serotypes (27 out of 115, 23.5%). An immune evaluation was undertaken in 28 children who received ≥2 PCV13 doses before IPD caused by a PCV13 serotype. Only 1 was found to have an immunodeficiency.

CONCLUSIONS

PCV13 serotypes (especially serotypes 3, 19A, and 19F) continue to account for nearly a quarter of IPD in US children 4 to 7 years after PCV13 was introduced. Underlying conditions are more common in children with non-PCV13 serotype IPD. Immune evaluations in otherwise healthy children with PCV13 serotype IPD despite receiving ≥2 PCV13 doses did not identify an immunodeficiency.

Impact of Childhood Pneumococcal Conjugate Vaccine on Nonnotified Clinically Suspected Invasive Pneumococcal Disease in Australia

BACKGROUND

Finnish studies have shown a significant impact of 10-valent pneumococcal conjugate vaccine (PCV10) on nonnotified clinically suspected invasive pneumococcal disease (IPD). We used a similar vaccine probe design to estimate PCV7 and PCV13 impact in Australian children.

METHODS

Season and age-matched pre-PCV7 cohorts (born in 2002-2004) were compared with PCV7-early and PCV7-late, and PCV13-eligible cohorts. Using linked notification and hospitalization data, we calculated relative rate reductions (RRRs) and absolute rate reductions (ARRs) for notified IPD, and nonnotified clinically suspected IPD or unspecified sepsis (first hospitalization with an International Classification of Diseases 10th Revision-Australian Modification code: A40.3/G00.1/M00.1 or A40.9/A41.9/A49.9/G00/I30.1/M00, respectively).

RESULTS

Significant reductions in all outcomes were observed comparing PCV7-early and PCV7-late and PCV13-eligible to pre-PCV7 cohorts. RRRs were high for both notified and nonnotified clinically suspected IPD (range 71%-91%), but ARRs were lower for nonnotified (5-6/100,000 person-years) than for notified cases (59-70/100,000 person-years). RRRs for the combined outcome of nonnotified clinically suspected IPD or unspecified sepsis were lower at 21%-24% for PCV7-eligible cohorts and 36% for the PCV13-eligible cohort, but ARRs were considerable due to the high pre-PCV7 rates (ARR 37-31/100,000 person-years for PCV7-early and PCV7-late cohorts and 54/100,000 person-years for PCV13).

CONCLUSIONS

This study provides a quantitative estimate of the total burden of IPD preventable by PCV7 and PCV13 vaccination programs in Australia. ARRs (compared with prevaccination) were significant but smaller than in Finland (122/100,000 for the combined outcome) and longer-term follow-up is required to determine the additional impact of PCV13 above that seen for PCV7. Country-specific studies are needed to accurately estimate the burden of pneumococcal disease preventable by vaccination and cost-effectiveness of PCV vaccination programs.

Persistence of pneumococcal antibodies after primary immunisation with a polysaccharide-protein conjugate vaccine

INTRODUCTION

Despite immunisation, antibiotics and intensive care management, infection with Streptococcus pneumoniae remains a major cause of morbidity and mortality in children. The WHO currently recommends vaccinating infants with either a 3+0 schedule (6 weeks, 3-4 and 4-6 months of age) or 2+1 schedule (2 doses before 6 months of age, plus a booster dose at 9-15 months of age). This study investigated pneumococcal antibody responses, including persistence of antibodies, after immunisation of healthy infants with a 3+0 schedule.

METHODS

We measured pneumococcal antibody concentrations to all 13 antigens included in the 13-valent pneumococcal conjugate vaccine (PCV13) after immunisation with a 3+0 schedule in 91 infants at 7 months and in 311 infants at 13 months of age. The geometric mean concentrations (GMCs) and the proportion of infants with an antibody concentration above the standard threshold correlate of protection (seroprotection rate) were calculated at both time points.

RESULTS

At 7 months of age, GMCs varied between 0.52 µg/mLand 11.52 µg/mL, and seroprotection rates varied between 69% and 100%. At 13 months of age, GMCs had decreased to between 0.22 µg/mLand 3.09 µg/mL, with the lowest responses against serotype 4, followed by 19A, 3, 6B and 23F. Seroprotection rates at 13 months of age were below 90% for most serotypes, with the lowest rates for serotype 4 (23%) followed by 19A (50%), 23F (61%) and 6B (64%).

CONCLUSION

Our study shows that at 13 months of age, many infants vaccinated with a 3+0 schedule have pneumococcal antibody concentrations below the standard threshold correlate of protection. To optimise protection against pneumococcal disease through early childhood and to improve antibody persistence and indirect protective effects, immunisation schedules with booster doses might be necessary.

Change in Pneumococcus Serotypes but not Mortality or Morbidity in Pre- and Post-13-Valent Polysaccharide Conjugate Vaccine Era: Epidemiology in a Pediatric Intensive Care Unit over 10 Years

AIM

Pneumococcus is a common commensal and an important pathogen among children for which immunization is available. Some serotypes occasionally cause severe pneumococcal disease with high mortality and morbidity. We reviewed all pneumococcal serotypes and mortality/morbidity in a pediatric intensive care unit (PICU) following universal pneumococcal conjugate vaccine (PCV) immunization.

METHODS

A 13-valent PCV was introduced in the universal immunization program in late 2011 in Hong Kong. We retrospectively reviewed all pneumococcal serotypes in the pre-(2007-11) and post-(2012-16) 13-valent PCV era.

RESULTS

There were 29 (1.9%) PICU patients with pneumococcal isolation, of which 6 died (20% motality). Serogroups 6 and 19 predominated before and Serogroup 3 after 2012. In the post-13-valent PCV era, the prevalence of pneumococcus isolation in PICU was increased from 1 to 2% (p = 0.04); Serogroup 3 was the major serotype of morbidity, despite supposedly under vaccine coverage. The majority of pneumococcus were penicillin-sensitive (94%) in the post 13-valent PCV era. All pneumococcus specimens were sensitive to cefotaxime and vancomycin. Binary logistic regression showed that there were reductions in Serogroup 6 (odds ratio [OR], 0.050; 95% confidence interval [CI], 0.004-0.574; p = 0.016) and Serogroup 19 (odds ratio [OR], 0.105; 95% confidence interval [CI], 0.014-0.786; p = 0.028) but not mortality or morbidity for patients admitted after 2012.

CONCLUSIONS

SPD is associated with significant morbidity and mortality, despite treatment with systemic antibiotics and ICU support. The expanded coverage of 13-valent PCV results in the reduction of Serotypes 6 and 19 but not mortality/morbidity associated with SPD in the setting of a PICU.