Trends in pneumococcal meningitis hospitalizations following the introduction of the 13-valent pneumococcal conjugate vaccine in the United States

Advances in the pathogenesis and treatment of pneumococcal meningitis

Streptococcus pneumoniae is a common pathogen associated with community-acquired bacterial meningitis, characterized by high morbidity and mortality rates. While vaccination reduces the incidence of meningitis, many survivors experience severe brain damage and corresponding sequelae. The pathogenesis of pneumococcal meningitis has not been fully elucidated. Currently, meningitis requires bacterial disruption of the blood - brain barrier, a process that involves the interaction of bacterial surface components with host cells and various inflammatory responses. This review delineates the global prevalence, pathogenesis, and treatment strategies of pneumococcal meningitis. The objective is to enhance the thorough comprehension of the clinical manifestations and biological mechanisms of the disease, thereby enabling more efficient prevention, diagnosis, and therapeutic interventions.

How common is otogenic meningitis? A retrospective study in southern Sweden over 18 years

BACKGROUND

Bacterial meningitis is a rare, but life-threatening disease, which sometimes occurs as a complication to acute otitis media (AOM). The proportion of meningitis cases originating from AOM is not clear.

PURPOSE

The aim of this study was to investigate the proportion of meningitis cases caused by AOM, to compare risk factors, bacteriology and outcome between otogenic and non-otogenic meningitis, and to analyse the incidence of bacterial meningitis after the introduction of conjugate pneumococcal vaccines (PCV).

METHODS

The medical charts of all patients admitted to hospitals in southern Sweden with bacterial meningitis between 2000 and 2017 were retrieved. Based on otoscopy and/or imaging, the proportion of otogenic meningitis cases was calculated, as were annual incidences.

RESULTS

A total of 216 patients were identified, 25 of whom died. The proportion of otogenic meningitis was 31% but varied from 6% among teenagers to 40% among adults. Before PCV, 23% of all meningitis cases were children < 2 years, compared to 1% post-PCV. The average incidence in the adult population, on the other hand, increased post-PCV, though there were large annual variations. S. pneumoniae was the most commonly identified pathogen in everyone but teenagers, in whom N. meningitidis was predominant.

CONCLUSION

AOM is an important cause of meningitis in children and adults. Though bacterial meningitis almost disappeared in children < 2 years after the introduction of PCV, the incidence of pneumococcal meningitis in adults seems to have increased.

Recognition and Outcomes of Pneumococcal Meningitis in 2 Tertiary Pediatric Hospitals Since the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine

OBJECTIVES

The aims of the study were to analyze the demographics, presentation, laboratory findings, and complications of pediatric Streptococcus pneumoniae meningitis since the introduction of the 13-valent pneumococcal conjugate vaccine, to improve recognition, and to minimize patient morbidity and mortality.

METHODS

This study used a retrospective analysis of pediatric pneumococcal meningitis cases at 2 tertiary healthcare systems in the Southeastern United States from 2010 to 2018.

RESULTS

We describe 21 cases of pneumococcal meningitis. All patients presented with fever, 95% had altered mental status by history or examination, and 48% had meningeal signs. Forty-three percent had seen another provider within 48 hours of admission. Forty-eight percent had delay in lumbar puncture (LP) of more than 6 hours after antibiotic administration, decreasing rates of positive cerebrospinal fluid cultures from 100% to 40% (P < 0.001). Decision to delay LP was due to either low suspicion for meningitis (n = 4) or clinical instability (n = 6) and was associated with lower rates of meningeal signs (P = 0.014) and higher rates of altered mental status on examination (P = 0.031). Fourteen patients (67%) were up-to-date on pneumococcal immunization. Serotypes were determined in 16 cases, with 2 patients (13%) immunized against the strain that infected them. Primary outcomes included seizures (48%), hearing loss (48%), cranial nerve palsy (33%), and death (5%). Delay in LP with low suspicion for meningitis was associated with longer hospital length of stay approaching statistical significance (P = 0.053).

CONCLUSIONS

Pneumococcal meningitis remains a relevant and potentially fatal disease despite widespread use of 13-valent pneumococcal conjugate vaccine. Its diagnosis is often delayed during interactions with physicians, which may put patients at increased risk for poor clinical outcomes.

Community-acquired bacterial meningitis

Progress has been made in the prevention and treatment of community-acquired bacterial meningitis during the past three decades but the burden of the disease remains high globally. Conjugate vaccines against the three most common causative pathogens (Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae) have reduced the incidence of disease, but with the replacement by non-vaccine pneumococcal serotypes and the emergence of bacterial strains with reduced susceptibility to antimicrobial treatment, meningitis continues to pose a major health challenge worldwide. In patients presenting with bacterial meningitis, typical clinical characteristics (such as the classic triad of neck stiffness, fever, and an altered mental status) might be absent and cerebrospinal fluid examination for biochemistry, microscopy, culture, and PCR to identify bacterial DNA are essential for the diagnosis. Multiplex PCR point-of-care panels in cerebrospinal fluid show promise in accelerating the diagnosis, but diagnostic accuracy studies to justify routine implementation are scarce and randomised, controlled studies are absent. Early administration of antimicrobial treatment (within 1 hour of presentation) improves outcomes and needs to be adjusted according to local emergence of drug resistance. Adjunctive dexamethasone treatment has proven efficacy beyond the neonatal age but only in patients from high-income countries. Further progress can be expected from implementing preventive measures, especially the development of new vaccines, implementation of hospital protocols aimed at early treatment, and new treatments targeting checkpoints of the inflammatory cascade.

Synthesis and delivery of Streptococcus pneumoniae capsular polysaccharides by recombinant attenuated Salmonella vaccines

Pneumococcal infection-caused diseases are responsible for substantial morbidity and mortality worldwide. Traditional pneumococcal vaccines are developed based on purified capsular polysaccharides (CPS) or CPS conjugated to a protein carrier. Production processes of the traditional vaccines are laborious, and thereby increase the vaccine cost and limit their use in developing nations. A cost-effective pneumococcal vaccine using the recombinant attenuated Salmonella vaccine (RASV) was developed in this study. We cloned and expressed genes for seven serotypes of CPSs in the RASV strain. The RASV-delivered CPSs induced robust humoral and cell-mediated responses and mediated efficient protection of mice against pneumococcal infection. Our work provides an innovative strategy for mass producing low-cost bioconjugated polysaccharide vaccines for needle-free mucosal delivery against pneumococcal infections.

Streptococcus pneumoniae capsular polysaccharides (CPSs) are major determinants of bacterial pathogenicity. CPSs of different serotypes form the main components of the pneumococcal vaccines Pneumovax, Prevnar7, and Prevnar13, which substantially reduced the S. pneumoniae disease burden in developed countries. However, the laborious production processes of traditional polysaccharide-based vaccines have raised the cost of the vaccines and limited their impact in developing countries. The aim of this study is to develop a kind of low-cost live vaccine based on using the recombinant attenuated Salmonella vaccine (RASV) system to protect against pneumococcal infections. We cloned genes for seven different serotypes of CPSs to be expressed by the RASV strain. Oral immunization of mice with the RASV-CPS strains elicited robust Th1 biased adaptive immune responses. All the CPS-specific antisera mediated opsonophagocytic killing of the corresponding serotype of S. pneumoniae in vitro. The RASV-CPS2 and RASV-CPS3 strains provided efficient protection of mice against challenge infections with either S. pneumoniae strain D39 or WU2. Synthesis and delivery of S. pneumoniae CPSs using the RASV strains provide an innovative strategy for low-cost pneumococcal vaccine development, production, and use.

Long-term population effects of infant 10-valent pneumococcal conjugate vaccination on pneumococcal meningitis in Finland

BACKGROUND

No previous studies have reported long-term follow-up of ten-valent pneumococcal conjugate vaccine (PCV10) program impact on pneumococcal meningitis (PM). We assessed the effects of infant PCV10 program on PM incidence, mortality and serotype distribution in children and adults during 7 years after introduction.

METHODS

We conducted a population-based observational study. A case of PM was defined as isolation of Streptococcus pneumoniae from cerebrospinal fluid or, a patient with S. pneumoniae isolated from blood and an ICD-10 hospital discharge diagnosis of bacterial meningitis within 30 days before or after positive culture date.We compared age- and serotype-specific incidence and associated 30-day mortality rates in 2011-2017 (PCV10 period) with those in 2004-2010 (pre-PCV10 baseline) by using Poisson regression models. Absolute rate differences and 95% confidence intervals (CIs) were calculated from the parameter estimates by using delta method.

RESULTS

During the PCV10 period, the overall incidence of PCV10 serotype meningitis decreased by 68% (95%CI 57%-77%), and the overall PM incidence by 27% (95%CI: 12%-39%). In age groups 0-4, 50-64, and ≥ 18 years, the overall PM incidence was reduced by 64%, 34% and 19%, respectively. In adults ≥ 65 years of age, a 69% reduction in PCV10 serotypes was offset by 157% (56%-342%) increase in non-PCV10 serotypes. The overall PM-related mortality rate decreased by 42% (95%CI 4%-65%). Overall case fatality proportion (CFP) was 16% in pre-PCV10 period and 12% in PCV10 period (p = 0.41); among persons 50-64 years the CFP decreased from 25% to 10% (p = 0.04).

CONCLUSIONS

We observed substantial impact and herd protection for vaccine-serotype PM and associated mortality after infant PCV10 introduction. However, in older adults ≥ 65 years of age, PM burden remains unchanged due to serotype replacement.

Pneumococcal vaccination coverage among adults aged 19 to 64 years with immuno-compromising conditions, cerebrospinal fluid (CSF) leaks, or cochlear implants in the US

Background: Adults with immuno-compromising conditions, CSF leaks, or cochlear implants are at increased risk for pneumococcal disease (high-risk patients), yet pneumococcal vaccination rates in the US for this group are low.Methods: A retrospective cohort analysis was conducted from 2010 to 2018 using the Truven Health MarketScan database to estimate pneumococcal vaccination coverage among adults aged 19 to 64 years newly diagnosed with high-risk conditions, and to assess factors associated with receiving the recommended pneumococcal vaccines.Results: The study sample included 2,497,799 adults aged 19 to 64 years old with newly diagnosed high-risk conditions. Most of the study cohort had seven or more annual physician office (52%) and pharmacy (56%) visits. The proportion of high-risk adults who received at least one pneumococcal vaccination increased from 5.4% after 1 year of follow-up to 14.2% after 6 years of follow-up. Compared to those who received no pneumococcal vaccination, high-risk adults who received any pneumococcal vaccination were more likely to be older, female, enrolled in an HMO, had more healthcare encounters, and were treated by a primary care provider.Conclusion: Despite numerous healthcare encounters annually, very few high-risk adults received pneumococcal vaccines, highlighting the need for implementing targeted interventions to increase vaccine uptake in this vulnerable population.

Pathology Associated With Streptococcus spp. Infection in Baboons (Papio spp.)

Streptococcus spp. are a source of morbidity and mortality in captive nonhuman primate populations. However, little is known about the lesions associated with naturally occurring streptococcal infections in baboons (Papio spp.). The pathology database of the Southwest National Primate Research Center was searched for all baboon autopsies from 1988 to 2018 in which Streptococcus spp. were cultured. Baboons on experimental protocol were excluded. The gross autopsy and histopathology reports were reviewed. Archived specimens were retrieved and reviewed as needed for confirmation or clarification. Fifty-six cultures were positive for Streptococcus spp. in 54 baboons with evidence of bacterial infection. Associated gross lesions included purulent exudate, fibrinous to fibrous adhesions, hemorrhage, mucosal thickening, organomegaly, and abscessation. Histologic lesions included suppurative inflammation, abscessation, necrosis, hemorrhage, fibrin accumulation, and thrombosis. Lungs and pleura (n = 31) were the most commonly infected organ followed by the central nervous system (n = 16), spleen (n = 15), soft tissues (n = 12), air sacs, liver, peritoneum, adrenal glands, heart, lymph nodes, uterus, kidneys, biliary system, bones, ears, umbilical structures, mammary glands, pancreas, placenta, and salivary glands. Infections by non-β-hemolytic Streptococcus spp. predominated in the lungs and air sacs; the most common isolate was Streptococcus pneumoniae. Infections by β-hemolytic Streptococcus spp. predominated in the soft tissues and reproductive tract. Naturally occurring β-hemolytic and non-β-hemolytic Streptococcus spp. infections cause morbidity and mortality in captive baboon populations. The lesions associated with streptococcal infection are similar to those reported in human infection. Thus, the baboon may represent an underutilized model for studying Streptococcus spp. as pathogens.

Adult Otogenic Meningitis in the Pneumococcal Conjugated Vaccines Era

Introduction   Streptococcus pneumoniae is a major pathogen of otogenic meningitis (OgM), the most commonly reported intra-cranial complication of otitis media (OM). Objectives  To study the changes in adult OgM patients in the pneumococcal conjugated vaccines (PCVs) era. Methods  Retrospective cohort of adults presenting with concurrent OM and meningitis in a secondary medical care center between 2005 and 2015. Data collected included demographics, OM-related symptoms, cerebrospinal fluid (CSF) and ear culture results, pre- and during hospitalization antibiotic treatment, imaging findings, and complications. We compared the pre-PCV years (2005-2009) with the post-PCV years (2010-2015). Outcomes were 1) incidence of all-cause adult OgM from the total meningitis cases; 2) impact of PCVs on the clinical presentation of OgM and bacteriology. Results  Otogenic meningitis was diagnosed in 26 out of 45 (58%) cases of all-cause meningitis admissions. Of those, 10 (38%) were male, with a mean age of 62.4 years old. Ear-related signs and symptoms were documented in 70% of the patients, and OgM was diagnosed following imaging studies in 6 out of 26 (23%) patients. All of the patients received intravenous antibiotic therapy, and 7 (27%) patients required surgical interventions: 6 required myringotomy and 1 required mastoidectomy. There were 12 (46%) patients in the pre-PCV years and 14 (56%) in the post-PCV years. The positive pneumococcal CSF and ear culture rates remained high and unchanged (∼ 75%). There were no significant changes in the clinical presentation or mortality rates. Conclusion  Micro-otoscopy should be included in the routine work-up of any suspected adult meningitis, because OgM is underdiagnosed. Unlike their impact on pediatric otitis media, PCVs did not change the epidemiology and bacteriology of OgM.

Trends in Pediatric Primary Care Visits Among Commercially Insured US Children, 2008-2016

IMPORTANCE

Primary care is the foundation of pediatric care. While policy interventions have focused on improving access and quality of primary care, trends in overall use of primary care among children have not been described.

OBJECTIVE

To assess trends in primary care visit rates and out-of-pocket costs, to examine variation in these trends by patient and visit characteristics, and to assess shifts to alternative care options (eg, retail clinics, urgent care, and telemedicine).

DESIGN, SETTING, AND PARTICIPANTS

Observational cohort study of claims data from 2008 to 2016 for children 17 years and younger covered by a large national commercial health plan. Visit rate per 100 child-years was determined for each year overall, by child and geographic characteristics, and by visit type (eg, primary diagnosis), and trends were assessed with a series of child-year Poisson models. Data were analyzed from November 2017 to September 2019.

MAIN OUTCOMES AND MEASURES

Visits to primary care and other settings.

RESULTS

This cohort study included more than 71 million pediatric primary care visits over 29 million pediatric child-years (51% male in 2008 and 2016; 37% between 12-17 years in 2008 and 38% between 12-17 years in 2016). Unadjusted results for primary care visit rates per 100 child-years decreased from 259.6 in 2008 to 227.2 in 2016, yielding a regression-estimated change in primary care visits across the 9 years of -14.4% (95% CI, -15.0% to -13.9%; absolute change: -32.4 visits per 100 child-years). After controlling for shifts in demographics, the relative decrease was -12.8% (95% CI, -13.3% to -12.2%). Preventive care visits per 100 child-years increased from 74.9 in 2008 to 83.2 visits in 2016 (9.9% change in visit rate; 95% CI, 9.0%-10.9%; absolute change: 8.3 visits per 100 child-years), while problem-based visits per 100 child-years decreased from 184.7 in 2008 to 144.1 in 2016 (-24.1%; 95% CI, -24.6% to -23.5%; absolute change: -40.6 visits per 100 child-years). Visit rates decreased for all diagnostic groups except for the behavioral and psychiatric category. Out-of-pocket costs for problem-based primary care visits increased by 42% during the same period. Per 100 child-years, visits to other acute care venues increased from 21.3 to 27.6 (30.3%; 95% CI, 28.5% to 32.1%; absolute change: 6.3 visits per 100 child-years) and visits to specialists from 45.2 to 53.5 (16.4%; 95% CI, 14.8% to 18.0%, absolute change: 8.3 visits per 100 child-years).

CONCLUSIONS AND RELEVANCE

Primary care visit rates among commercially insured children decreased over the last decade. Increases in out-of-pocket costs and shifts to other venues appear to explain some of this decrease.

Recurrent Pneumococcal Meningitis Secondary to Nasoethmoidal Meningocele

Since the widespread introduction of the conjugate pneumococcal vaccine and subsequent decline of invasive pneumococcal disease in children, a significant proportion of children with pneumococcal meningitis are identified as having an underlying immunodeficiency or predisposing anatomic abnormality. We present 3 cases of recurrent pneumococcal meningitis where detailed neuro-imaging revealed subtle anterior base of skull defects not detected on initial investigations.

Effect of Pneumococcal Conjugate Vaccines on Pneumococcal Meningitis, England and Wales, July 1, 2000-June 30, 2016

We describe the effects of the 7-valent (PCV7) and 13-valent (PCV13) pneumococcal conjugate vaccines on pneumococcal meningitis in England and Wales during July 1, 2000–June 30, 2016. Overall, 84,473 laboratory-confirmed invasive pneumococcal disease cases, including 4,160 (4.9%) cases with meningitis, occurred. PCV7 implementation in 2006 did not lower overall pneumococcal meningitis incidence because of replacement with non–PCV7-type meningitis incidence. Replacement with PCV13 in 2010, however, led to a 48% reduction in pneumococcal meningitis incidence by 2015–16. The overall case-fatality rate was 17.5%: 10.7% among patients <5 years of age, 17.3% among patients 5–64 years of age, and 31.9% among patients >65 years of age. Serotype 8 was associated with increased odds of death (adjusted odds ratio 2.9, 95% CI 1.8–4.7). In England and Wales, an effect on pneumococcal meningitis was observed only after PCV13 implementation. Further studies are needed to assess pneumococcal meningitis caused by the replacing serotypes.

Resurgence of pneumococcal meningitis in Europe and Northern America

BACKGROUND

Streptococcus pneumoniae is the most common pathogen causing bacterial meningitis. The routine use of multivalent conjugate pneumococcal vaccines has led to a decline of invasive pneumococcal disease caused by serotypes included in the vaccine serotypes. Recently, several reports have described a concomitant rise in the incidence of non-vaccine serotypes, suggesting serotype replacement.

OBJECTIVE

We aim to review the effect of pneumococcal vaccination on the incidence of pneumococcal meningitis in Europe and northern America with a particular interest in serotype replacement.

SOURCES

Articles that include data on invasive pneumococcal disease incidence before and after the introduction of vaccination, or on invasive pneumococcal serotype, are discussed, with a focus on pneumococcal meningitis.

CONTENT

The introduction of pneumococcal conjugate vaccines has universally resulted in a decline in vaccine-serotype pneumococcal meningitis incidence throughout Europe and northern America. Serotype replacement by non-vaccine serotypes has however been reported following the introduction of the 7-, 10- and 13-valent pneumococcal conjugate vaccines, which in several regions abolished the overall effect of vaccination on pneumococcal meningitis incidence.

IMPLICATIONS

The promising decline in the incidence of pneumococcal meningitis following the introduction of vaccination seems to have been temporary. Replacement by non-vaccine serotypes illustrates that pneumococcal meningitis continues to pose a major challenge. We need new approaches to prevention, new vaccines and continued efforts to improve treatment for patients with pneumococcal meningitis.

Pediatric meningitis due to Neisseria meningitidis, Streptococcus pneumoniae and Group B Streptococcus in Tijuana, Mexico: active/prospective surveillance, 2005-2018

Introduction

In Mexico, Neisseria meningitidis is considered to be a rare cause of bacterial meningitis (BM), however, one national publication using active surveillance has suggested the opposite. Group B Streptococcus (GBS) is also considered to be infrequent in young infants as a cause of BM in central Mexico. Streptococcus pneumoniae vaccination using the 13-valent conjugate vaccine (PCV13) started in our region in May 2012. We focused our research on whether N. meningitidis and GBS are important causes of BM, and to examine the effectiveness of PCV13 on pneumococcal BM.

Methods

From October 2005 to September 2018, active/prospective surveillance looking for all patients admitted with suspected BM <16 years of age was performed at the Tijuana, Mexico, General Hospital. Tijuana, Mexico to San Diego, Unites States of America (USA), is the most transited border in the world. Isolation of pathogens was by either conventional culture or Real Time-polymerase chain reaction (RT-PCR), all patients were followed during and 3 months after discharge, and a descriptive analysis was performed. The effectiveness of PCV13 was determined by comparing the proportion of cases per month on pneumococcal BM before and after its implementation.

Results

There were 86 confirmed BM cases. N. meningitidis was the leading cause (60.5%, and 61.5% caused by serogroup C), followed by S. pneumoniae (18.6%). PCV13 effectiveness on pneumococcal BM was of 64.3% and was associated with the disappearance of serotype 19A. A total of 22 infants <3 months old had BM; GBS was the leading cause at this age group (27.3%), followed by N. meningitidis (22.7%). The overall mortality was 24%.

Conclusions

BM by N. meningitidis is endemic in Tijuana, Mexico, and meningococcal vaccination should be seriously considered in the region. PCV13 is currently showing high effectiveness on pneumococcal BM, and we need to continue active surveillance to see whether maternal screening/prophylaxis for GBS should also be introduced in the region.

A recombinant conjugated pneumococcal vaccine that protects against murine infections with a similar efficacy to Prevnar-13

The pneumococcal conjugate vaccine (PCV) strongly protects against vaccine serotypes, but the rapid expansion of non-vaccine serotype disease and the vaccine's high expense has reduced its overall impact. We have developed Protein Glycan Coupling Technology (PGCT) as a flexible methodology for making low-cost polysaccharide/protein glycoconjugates recombinantly in Escherichia coli. We have used PGCT to make a recombinant PCV containing serotype 4 capsular polysaccharide linked to the Streptococcus pneumoniae proteins NanA, PiuA, and Sp0148. The introduction of the Campylobacter jejuni UDP-glucose 4-epimerase gene GalE (gne) into E. coli improved the yield of the resulting glycoprotein. PGCT glycoconjugate vaccination generated strong antibody responses in mice to both the capsule and the carrier protein antigens, with the PiuA/capsule glycoconjugate inducing similar anti-capsular antibody responses as the commercial PCV Prevnar-13. Antibody responses to PGCT glycoconjugates opsonised S. pneumoniae and Streptococcus mitis expressing the serotype 4 capsule and promoted neutrophil phagocytosis of S. pneumoniae to a similar level as antisera generated by vaccination with Prevnar-13. Vaccination with the PGCT glycoconjugates protected mice against meningitis and septicaemia with the same efficacy as vaccination with Prevnar-13. In addition, vaccination with the protein antigen components from PGCT glycoconjugates alone provided partial protection against septicaemia and colonisation. These data demonstrate that a vaccine made by PGCT is as effective as Prevnar-13, identifies PiuA as a carrier protein for glycoconjugate vaccines, and demonstrates that linking capsular antigen to S. pneumoniae protein antigens has additional protective benefits that could provide a degree of serotype-independent immunity.

Incidence of paediatric pneumococcal meningitis and emergence of new serotypes: a time-series analysis of a 16-year French national survey

BACKGROUND

Successive implementation of seven-valent then 13-valent pneumococcal conjugate vaccines (PCVs) led to a marked decrease in pneumococcal disease burden, including pneumococcal meningitis. We assessed the long-term effect of implementation of PCVs on incidence of pneumococcal meningitis in children in France over a 16-year period.

METHODS

We did a quasi-experimental, population-based interrupted time-series analysis with a nationwide prospective survey over 16 years in France, recruiting children aged younger than 15 years from 227 paediatric wards from January, 2001, to December, 2016. The main outcome by the time-series model was the estimated incidence of pneumococcal meningitis per 100 000 children (of a population of 12·6 million children in 2017) before and after PCV7 and PCV13 implementation. The time-series model was based on segmented regression with autoregressive error.

FINDINGS

We enrolled 1778 children with pneumococcal meningitis. PCV13 implementation led to a significant reduction in monthly incidence of pneumococcal meningitis from 0·12 per 100 000 children before PCV13 to a nadir of 0·07 in December, 2014 (-38%, 95% CI -56·1 to -20·4; p<0·0001). A sharp increase occurred during 2015 and 2016, (+2·3% per month, incidence of 0·13 per 100 000 children at the end of the study period, p=0·0002), mainly related to an increase of serotype 24F, which was frequently penicillin resistant.

INTERPRETATION

The early effect of PCV13 implementation greatly reduced the incidence of pneumococcal meningitis in children less than 15 years old. However, a sharp rebound in incidence linked to the emergence of serotype 24F compromised the long-term PCV efficacy. If confirmed in future studies and in other countries, pneumococcal meningitis incidence rebound and 24F emergence should be considered when developing next-generation PCVs.

FUNDING

The French Pediatric Infectious Diseases Group, Association Clinique et Thérapeutique Infantile du Val de Marne, Pfizer, and for the National Reference Centre for Pneumococci, the French National Health Agency.

Room Temperature Stable PspA-Based Nanovaccine Induces Protective Immunity

Streptococcus pneumoniae is a major causative agent of pneumonia, a debilitating disease particularly in young and elderly populations, and is the leading worldwide cause of death in children under the age of five. While there are existing vaccines against S. pneumoniae, none are protective across all serotypes. Pneumococcal surface protein A (PspA), a key virulence factor of S. pneumoniae, is an antigen that may be incorporated into future vaccines to address the immunological challenges presented by the diversity of capsular antigens. PspA has been shown to be immunogenic and capable of initiating a humoral immune response that is reactive across approximately 94% of pneumococcal strains. Biodegradable polyanhydrides have been studied as a nanoparticle-based vaccine (i.e., nanovaccine) platform to stabilize labile proteins, to provide adjuvanticity, and enhance patient compliance by providing protective immunity in a single dose. In this study, we designed a room temperature stable PspA-based polyanhydride nanovaccine that eliminated the need for a free protein component (i.e., 100% encapsulated within the nanoparticles). Mice were immunized once with the lead nanovaccine and upon challenge, presented significantly higher survival rates than animals immunized with soluble protein alone, even with a 25-fold reduction in protein dose. This lead nanovaccine formulation performed similarly to protein adjuvanted with Alum, however, with much less tissue reactogenicity at the site of immunization. By eliminating the free PspA from the nanovaccine formulation, the lead nanovaccine was efficacious after being stored dry for 60 days at room temperature, breaking the need for maintaining the cold chain. Altogether, this study demonstrated that a single dose PspA-based nanovaccine against S. pneumoniae induced protective immunity and provided thermal stability when stored at room temperature for at least 60 days.