Pneumococcal disease in South Australia: vaccine success but no time for complacency

Indirect (herd) protection, following pneumococcal conjugated vaccines introduction: A systematic review of the literature

BACKGROUND

Pneumococcal diseases are major causes of morbidity among adults, especially those over 50years of age. While pneumococcal conjugated vaccines (PCV's) impact on pneumococcal disease rates among children is well established, the extent of its impact on adult pneumococcal related illness remains unclear. The aim of this systematic literature review was to describe the impact of PCV introduction to childhood national immunization programs worldwide on PCV-naive adult population.

METHODS

A systematic literature search was performed using the PubMed database. The search was limited to articles written in English and published between January 2000 and February 2016. Studies evaluating pneumococcal disease rates in individuals over 5years of age were included. Independent extraction of articles was performed by the two authors. Search terms included: Pneumococcal conjugated vaccine, herd, indirect, adults, and pneumonia.

RESULTS

Forty-nine articles meeting the selection criteria were identified, 39 regarding invasive pneumococcal disease (IPD, one on meningitis only), 8 regarding pneumonia, and 2 on both IPD and pneumonia. The majority of reports were from the US, UK and Canada. Considerable variability in the data sources, quality and completeness was observed. While most studies reported either statistically significant reduction or insignificant changes in IPD and pneumonia disease rates in adults following PCV nationwide implementation, few studies reported statistically significant increase in pneumococcal disease rates, these were mainly from countries with low PCV coverage rates and/or inadequate surveillance.

CONCLUSION

Invasive pneumococcal diseases and pneumonia rates among the adult population decreased in most countries following PCV introduction into the NIP. This indirect effect on older population seems to be dependent on PCV coverage rates and time from PCV nationwide implementation. Adults >65years old seem to benefit the most from PCV introduction.

Invasive pneumococcal disease among adults in Japan, April 2013 to March 2015: disease characteristics and serotype distribution

BACKGROUND

In Japan, the clinical characteristics and recent serotype distribution among adult patients of invasive pneumococcal disease (IPD) have not been fully investigated since the introduction of the pneumococcal conjugate vaccine (PCV) in children. From November 2010, PCV7 was encouraged by an official program, funded by government, subsequently included in the routine schedule in April 2013, and replaced with a PCV13 in November 2013.

METHODS

Between April 2013 and March 2015, patients with IPD older than 15 years were evaluated based on the enhanced national surveillance in ten prefectures of Japan. The serotype distribution of the isolates was analyzed in these patients.

RESULTS

The analysis included 291 patients: 107 patients (37%) were female and the median age was 70 years. Of 281 patients with available data, 202 (72%) had underlying diseases, including 107 patients (38%) with immunocompromised status. The case fatality proportion for all case was 20%. In subgroup analysis, the case fatality proportion (29%) in immunocompromised patients was much higher than that (0-16%) in each age group of nonimmunocompromised patients (15-39 years, 40-64 years, and ≥ 65 years). While the proportion of bacteremia without any focus (27%) was higher than that (8-10%) in nonimmunocompromised patients, the proportions of vaccine types (PCV13, 32%; PPSV23, 51%) of the causative isolates were lower than those in each age group of nonimmunocompromised patients. Among 291 isolates, the most frequent serotypes were 3 (17%), 19A (13%), and 22F (10%). Twelve percent of the isolates were PCV7 serotypes, 46% were PCV13 serotypes, and 66% were PPSV23 serotypes.

CONCLUSIONS

The majority of adult patients of IPD had underlying diseases, including immunocompromised conditions. A low proportion (12%) of PCV7-type IPD was observed in this population where PCV7 for children had been included in the routine immunization schedule.

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

BACKGROUND

In Japan, the seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in 2010. PCV13 has replaced PCV7 since November 2013.

METHODS

The effectiveness of PCV7 in protecting against invasive pneumococcal disease (IPD) in children aged <5 years was evaluated in a nationwide active population-based surveillance of IPD in 2008-2013 in 10 prefectures in Japan.

RESULTS

1181 cases were identified; 711 pneumococcal strains were analyzed for serotyping and antimicrobial resistance. Compared with the baseline IPD incidence (25.0 per 100,000), a 98% decline in IPD caused by PCV7 serotypes was found after the introduction of PCV7. This was partially offset by an increased incidence of IPD caused by PCV13 minus PCV7 and non-PCV13 serotypes, resulting in a 57% decline in overall IPD incidence. Absolute increases in the incidence rates of IPD caused by PCV13 minus PCV7 and non-PCV13 serotypes were 2.1 and 2.8 per 100,000 during the study period, respectively. The proportion of meropenem-nonsusceptible strains, especially with serotypes 19A and 15A, increased significantly after PCV7 introduction.

CONCLUSIONS

Our data confirmed a 98% decline in IPD incidence caused by PCV7 serotypes in children aged <5 years and serotype replacement after PCV7 introduction. This shows the importance of continuing surveillance of serotypes responsible for IPD and their antimicrobial resistance in Japan.

Effectiveness of 7-valent pneumococcal conjugate vaccine: A meta-analysis of post-marketing studies

AIM: To investigate the 7-valent pneumococcal conjugate vaccine (PCV7) effectiveness.

METHODS: A systematic literature review of studies which evaluated the effectiveness of PCV7 vaccine was performed searching the keyword “heptavalent pneumococcal conjugate vaccine” in PubMed and Scopus until March 16, 2013. The selection of potential eligible articles was done by two researchers independently on the basis of abstract and title and only post-marketing studies were included in the systematic review. Data extraction was carried out by two researchers with respect to invasive pneumococcal diseases due to both all and vaccine serotypes in pre-vaccine and post-vaccine periods in children less than 5 years. Results of studies which were considered suitable for meta-analysis were combined by means of relative risk (RR) with 95%CI. Vaccine effectiveness was calculated as (1-RR) × 100. Heterogeneity was assessed by I² and a random effects model was used to combine data in the case of heterogeneity. RevMan 5 was used to pool data.

RESULTS: On the whole, 757 eligible papers were identified from the literature search in PubMed and Scopus. Of them, 62 were finally considered in the systematic review and 38 were included in the meta-analysis. In all post-marketing studies included in the systematic review the incidence of invasive pneumococcal diseases due to vaccine serotypes declined significantly with the exception of few studies showing stability or a slight, but not significant, increase. Furthermore most of studies highlighted also a reduction in the incidence of invasive pneumococcal diseases due to all serotypes. With regards to meta-analysis, a random effects model was used to combine data because of the high heterogeneity. Data combination showed that the effectiveness of PCV7 in reducing invasive pneumococcal diseases due to vaccine serotypes and to all serotypes was 84% (95%CI: 74%-90%) and 53% (95%CI: 46%-59%) respectively. These results are confirmatory with respect to the efficacy of PCV7 against invasive pneumococcal diseases due to vaccine serotypes.

CONCLUSION: PCV7 implementation determines a significant decrease of invasive pneumococcal diseases.

Modified MLVA for Genotyping Queensland Invasive Streptococcus pneumoniae

Background

Globally, over 800 000 children under five die each year from infectious diseases caused by Streptococcus pneumoniae. To understand genetic relatedness between isolates, study transmission routes, assess the impact of human interventions e.g. vaccines, and determine infection sources, genotyping methods are required. The ‘gold standard’ genotyping method, Multi-Locus Sequence Typing (MLST), is useful for long-term and global studies. Another genotyping method, Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA), has emerged as a more discriminatory, inexpensive and faster technique; however there is no universally accepted method and it is currently suitable for short-term and localised epidemiology studies. Currently Australia has no national MLST database, nor has it adopted any MLVA method for short-term or localised studies. This study aims to improve S. pneumoniae genotyping methods by modifying the existing MLVA techniques to be more discriminatory, faster, cheaper and technically less demanding than previously published MLVA methods and MLST.

Methods

Four different MLVA protocols, including a modified method, were applied to 317 isolates of serotyped invasive S. pneumoniae isolated from sterile body sites of Queensland children under 15 years from 2007–2012. MLST was applied to 202 isolates for comparison.

Results

The modified MLVA4 is significantly more discriminatory than the ‘gold standard’ MLST method. MLVA4 has similar discrimination compared to other MLVA techniques in this study). The failure to amplify particular loci in previous MLVA methods were minimised in MLVA4. Failure to amplify BOX-13 and Spneu19 were found to be serotype specific.

Conclusion

We have modified a highly discriminatory MLVA technique for genotyping Queensland invasive S. pneumoniae. MLVA4 has the ability to enhance our understanding of the pneumococcal epidemiology and the changing genetics of the pneumococcus in localised and short-term studies.

Effectiveness of 7-valent pneumococcal conjugate vaccine against invasive pneumococcal disease in HIV-infected and -uninfected children in south africa: a matched case-control study

A 2 + 1 seven-valent pneumococcal conjugate vaccine schedule is effective against vaccine-serotype invasive pneumococcal disease (IPD) in HIV-uninfected children and HIV-exposed but -uninfected children and against all-serotype multidrug-resistant IPD in HIV-uninfected children.

Background. South Africa introduced 7-valent pneumococcal conjugate vaccine (PCV7) in April 2009 using a 2 + 1 schedule (6 and 14 weeks and 9 months). We estimated the effectiveness of ≥2 PCV7 doses against invasive pneumococcal disease (IPD) in human immunodeficiency virus (HIV)–infected and -uninfected children.

Methods. IPD (pneumococcus identified from a normally sterile site) cases were identified through national laboratory-based surveillance. Specimens were serotyped by Quellung or polymerase chain reaction. Four controls, matched for age, HIV status, and hospital were sought for each case. Using conditional logistic regression, we calculated vaccine effectiveness (VE) as 1 minus the adjusted odds ratio for vaccination.

Results. From March 2010 through November 2012, we enrolled 187 HIV-uninfected (48 [26%] vaccine serotype) and 109 HIV-infected (43 [39%] vaccine serotype) cases and 752 HIV-uninfected and 347 HIV-infected controls aged ≥16 weeks. Effectiveness of ≥2 PCV7 doses against vaccine-serotype IPD was 74% (95% confidence interval [CI], 25%–91%) among HIV-uninfected and −12% (95% CI, −449% to 77%) among HIV-infected children. Effectiveness of ≥3 doses against vaccine-serotype IPD was 90% (95% CI, 14%–99%) among HIV-uninfected and 57% (95% CI, −371% to 96%) among HIV-infected children. Among HIV-exposed but -uninfected children, effectiveness of ≥2 doses was 92% (95% CI, 47%–99%) against vaccine-serotype IPD. Effectiveness of ≥2 doses against all-serotype multidrug-resistant IPD was 96% (95% CI, 62%–100%) among HIV-uninfected children.

Conclusions. A 2 + 1 PCV7 schedule was effective in preventing vaccine-serotype IPD in HIV-uninfected and HIV-exposed, uninfected children. This finding supports the World Health Organization recommendation for this schedule as an alternative to a 3-dose primary series among HIV-uninfected individuals.

A randomized clinical trial of the immunogenicity of 7-valent pneumococcal conjugate vaccine compared to 23-valent polysaccharide vaccine in frail, hospitalized elderly

BACKGROUND

Elderly people do not mount strong immune responses to vaccines. We compared 23-valent capsular polysaccharide (23vPPV) alone versus 7-valent conjugate (PCV7) vaccine followed by 23vPPV 6 months later in hospitalized elderly.

METHODS

Participants were randomized to receive 23vPPV or PCV7-23vPPV. Antibodies against serotypes 3, 4, 6A, 6B, 9V, 14, 18C, 19A, 19F, 23F were measured by enzyme-linked immunosorbent (ELISA) and opsonophagocytic (OPA) assays at baseline, 6 months and 12 months.

RESULTS

Of 312 recruited, between 40% and 72% of subjects had undetectable OPA titres at baseline. After one dose, PCV7 recipients had significantly higher responses to serotypes 9V (both assays) and 23F (OPA only), and 23vPPV recipients had significantly higher responses to serotype 3 (ELISA), 19F and 19A (OPA only). In subjects with undetectable OPA titres at baseline, a proportionately greater rise in OPA titre (P<0.01) was seen for all serotypes after both vaccines. The GMT ratio of OPA was significantly higher at 12 months in the PCV7-23vPPV group for serotypes 6A, 9V, 18C and 23F. OPA titre levels for these serotypes increased moderately after 6 months, whereas immunity waned in the 23vPPV only arm.

CONCLUSION

We did not show overwhelming benefit of one vaccine over the other. Low baseline immunity does not preclude a robust immune response, reiterating the importance of vaccinating the frail elderly. A schedule of PCV7-23vPPV prevents waning of antibody, suggesting that both vaccines could be useful in the elderly. Follow up studies are needed to determine persistence of immunity.

TRIAL REGISTRATION

The Australian Clinical Trials Registry ACTRN12607000387426.

Towards New Broader Spectrum Pneumococcal Vaccines: The Future of Pneumococcal Disease Prevention

Seven-valent pneumococcal conjugate vaccine (PCV7) introduction and routine pediatric use has substantially reduced the burden of Streptococcus pneumoniae disease worldwide. However, a significant amount of disease burden, due to serotypes not contained in PCV7, still exists globally. A newly recognized serotype, 6C, was until recently, identified and reported as serotype 6A. This review summarizes the serotype epidemiology of pneumococcal disease pre- and post-introduction of PCV7, available post-marketing surveillance data following the introduction of higher valency pneumococcal vaccines (PCV10, PCV13) and future prospects for the development of new pneumococcal vaccines.

Pneumococcal serotype diversity among adults in various countries, influenced by pediatric pneumococcal vaccination uptake

Streptococcus pneumoniae serotypes differ in clinical manifestations among adults. Indirect effects of pediatric use of pneumococcal conjugate vaccines (PCVs) affect rates of adult serotype-specific invasive pneumococcal disease (IPD). To characterize PCV effect on adult serotype patterns, we reviewed the literature for differences in proportions and incidence matching the 23-valent pneumococcal polysaccharide vaccine (PPSV23) and 13-valent PCV within specified geographic and time conditions. For adult IPD serotype distribution before widespread pediatric PCV7 use, the median differential between the 23 and 13 serotypes was 16.3% in the core analysis. After pediatric PCV7 adoption, the median differential was 24.4% (P < .003).The median differential in IPD incidence among adults was 5.6 cases per 100 000 population before pediatric PCV7 use and 6.4 afterward (P = .52). The differential for the serotypes in alternate vaccines helps explain recent national recommendations for one or both vaccines in various populations. These differences may widen further, with more extensive pediatric uptake of higher-valence PCVs.

13-valent pneumococcal conjugate vaccine: a review of its use in infants, children, and adolescents

The 13-valent pneumococcal conjugate vaccine (Prevenar 13(®); Prevnar 13(®)) [PCV13] includes 13 serotype-specific polysaccharides of Streptococcus pneumoniae conjugated individually to non-toxic diphtheria CRM197 protein, thus providing wider coverage of pneumococcal serotypes than its 7-valent predecessor (PCV7). For pediatric populations, PCV13 was initially approved for use in infants and children up to 5 years of age, but recently received approval for expanded use (ages 6 weeks to 17 years) in the EU and the USA. This change in labeling was made primarily on the basis of results of Study 3011, which demonstrated the serotype-specific immunogenicity of a single dose of PCV13 in children ≥5 to <10 years of age who had previously received PCV7. Study 3011 also demonstrated functional immune responses after a single dose of PCV13 in a cohort ≥10 to <18 years of age who had not previously received PCV7. Importantly, prior to Study 3011, several randomized studies comparing PCV13 and PCV7 in infants and younger children demonstrated noninferiority of immune responses to the seven serotypes common to both vaccines after a two- or three-dose primary infant series and after the toddler booster dose; immunogenicity and functional immune responses were also demonstrated for the six additional serotypes. The safety and reactogenicity of PCV13 was generally similar to that of PCV7, and PCV13 did not interfere with the immune responses to coadministered routine pediatric vaccines. PCV13 is expected to substantially reduce the incidence of invasive pneumococcal diseases in a manner similar to that which occurred after PCV7 was introduced, and evidence of the protective effectiveness of PCV13 against pneumococcal diseases is emerging.

Impact of pneumococcal conjugate vaccines on nasopharyngeal carriage and invasive disease among unvaccinated people: review of evidence on indirect effects

BACKGROUND

Invasive disease due to Streptococcus pneumoniae remains an important worldwide cause of morbidity and mortality, particularly in young children and the elderly. The development and use of pneumococcal conjugate vaccines (PCVs) have had a dramatic impact on rates of vaccine-type invasive pneumococcal disease (IPD) not only in the pediatric population targeted for vaccination but in non-vaccinated age-groups as well. This indirect effect is directly mediated by a reduction of vaccine-type nasopharyngeal carriage and thus transmission by vaccinated children. Current PCV licensing procedures do not take into consideration nasopharyngeal carriage impact, and thus the indirect effect. This review summarizes the evidence for the indirect effect of PCV on vaccine-type disease and its correlation with changes in carriage among unvaccinated populations, to assess the basis for inclusion of carriage in the PCV licensing process.

METHODS

Randomized controlled trials, surveillance and other observational studies published between 1994 and 2013 were systematically identified from global, regional and review databases and conference abstracts. We included as primary evidence, studies in non-vaccinated groups addressing changes in both vaccine-type IPD and carriage between pre- and post-PCV introduction periods; studies missing one of these four components were included as supporting rather than primary evidence.

RESULTS

We identified studies from 14 countries, nearly all developed countries. Vaccine-type IPD and carriage in non-targeted populations consistently decreased after PCV introduction, with the magnitude of decrease growing over time. Where IPD and carriage were observed in the same population, VT-decreases occurred contemporaneously. These relationships held true across age-groups and between indigenous and non-indigenous populations in the US and Australia.

CONCLUSIONS

Indirect PCV impact on VT-IPD and VT-carriage has been significant. Impact on carriage should be considered for inclusion in the PCV licensure process as a predictor of indirect effects.

A nationwide surveillance of invasive pneumococcal disease in adults in Israel before an expected effect of PCV7

Pneumococcal infections in adults vary in severity and incidence is affected by childhood vaccination policy. Here, we try to define the host determinants and the interaction with specific serotypes that result in invasive pneumococcal disease (IPD) before an expected effect of pneumococcal conjugate vaccines. A nationwide active surveillance was initiated on July 2009, at the time of national implementation of PCV7 in Israel. The surveillance included all 27 laboratories and medical centers performing blood cultures in Israel, providing all blood and CSF pneumococcal isolates from persons ≥18y. Capture-recapture method assured that >95% of all cases were reported. IPD outcome and medical history were recorded and isolates were serotyped. Four hundred and sixty IPD cases were reported (annual incidence [/100,000] of 9.25). Incidence increased with age, from 2.6 among 18-34y to 66.8 among ≥85y. The most common diagnosis was pneumonia (72.4%), followed by bacteremia with no apparent focus (20.2%). Case fatality rate increased with age and number of comorbidities (34.5% for ≥75y or those with ≥3 comorbidities vs. 9.2-11.2% among <65y or those with no comorbidities; p=0.015). Variables independently associated with mortality were: age ≥75, chronic renal failure, malignancy, neurosurgery, alcohol abuse, multi-lobar pneumonia and sepsis with no apparent focus. The predominant serotypes in patients 18-49y were 1, 5, 8, 7F and 9V (constituting 56.3% in this age-group vs. 11.9% in ≥75y; p<0.01). The predominant serotypes among patients ≥75y were 3, 19A, 23F and 14 (40.3% of this age-group vs. 12.9% of 18-49y; p<0.01). Overall, PCV7 and PCV13 covered 25.6% and 63.7% of isolates, respectively, and 30.9% and 67.9% of isolates in mortality cases respectively. This nationwide active surveillance provides the baseline incidence, mortality rates and risk group distributions of IPD in adults before expected PCV effect.

Effectiveness of the ten-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against invasive pneumococcal disease: a cluster randomised trial

BACKGROUND

The Finnish Invasive Pneumococcal disease (FinIP) vaccine trial was designed to assess the effectiveness of a pneumococcal vaccine containing ten serotype-specific polysaccharides conjugated to Haemophilus influenzae protein D, tetanus toxoid, and diphtheria toxoid as the carrier proteins (PHiD-CV10) against invasive pneumococcal disease.

METHODS

In this cluster-randomised, double-blind trial, children aged younger than 19 months received PHiD-CV10 in 52 clusters or hepatitis vaccines as control in 26 clusters. Infants aged younger than 7 months at the first vaccination received either a 3+1 or a 2+1 vaccination schedule, children aged 7-11 months received a 2+1 schedule, and those 12-18 months of age received a two-dose schedule. The primary and secondary objectives were to assess vaccine effectiveness against culture-confirmed invasive pneumococcal disease due to any of the ten vaccine serotypes for the 3+1 and 2+1 schedules, respectively, in children who received at least one PHiD-CV10 dose before 7 months of age. Masked follow-up of pneumococcal disease lasted from the first vaccination (from February, 2009, to October, 2010) to January 31, 2012. Invasive disease data were retrieved from data accumulated in the national infectious diseases register. This trial and the nested acute otitis media trial are registered with ClinicalTrials.gov, numbers NCT00861380 and NCT00839254, respectively.

FINDINGS

47,369 children were enrolled from February, 2009, to October, 2010. 30,528 participants were assessed for the primary objective. 13 culture-confirmed vaccine-type cases of invasive pneumococcal disease were detected: none in the PHiD-CV10 3+1 group, one in the PHiD-CV10 2+1 group, and 12 in the control groups. The estimates for vaccine effectiveness were 100% (95% CI 83-100) for PHiD-CV10 3+1 and 92% (58-100) for PHiD-CV10 2+1 groups. Two cases of any culture-confirmed invasive disease irrespective of serotype were detected in combined PHiD-CV10 infant cohorts compared with 14 in the corresponding control cohorts (vaccine effectiveness 93%, 75-99). In catch-up cohorts, seven cases of invasive disease were reported, all in the control group: two cases in the children enrolled at 7-11 months of age; and five cases in children enrolled at 12-18 months of age (vaccine effectiveness 100%, 79-100). Non-fatal serious adverse events suspected to be vaccine-related were reported via routine post-immunisation safety surveillance in 18 children.

INTERPRETATION

This nationwide trial showed high PHiD-CV10 effectiveness against invasive pneumococcal disease when given in different schedules. For the first time, effectiveness of a 2+1 schedule in infants was confirmed in a clinical trial.

FUNDING

GlaxoSmithKline Biologicals SA and National Institute for Health and Welfare, Finland.

Increased paediatric hospitalizations for empyema in Australia after introduction of the 7-valent pneumococcal conjugate vaccine

OBJECTIVE

To examine rates of paediatric hospitalization for empyema and pneumonia in Australia before and after the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7).

METHODS

Rates of paediatric hospitalization for empyema and pneumonia (bacterial, viral and all types) were calculated following the codes of the International Classification of Diseases, tenth revision (ICD-10) as a principal diagnosis. The expected number of hospitalizations after the PCV7 was introduced was estimated on the basis of the observed number of hospitalizations before the introduction of the PCV7. Incidence rate differences (IRDs) and incidence rate ratios (IRRs) were calculated. Hospitalization incidence in each study period was expressed as the number of hospitalizations per million (10(6)) person-years. The population of children aged 0-19 years in Australia from 1998 to 2004 and from 2005 to 2010, as reported by the Australian Bureau of Statistics, was used to calculate the number of person-years in each period.

FINDINGS

In the 5 years following the introduction of the PCV7, hospitalizations for pneumonia were fewer than expected (15 304 fewer; 95% confidence interval, CI: 14 646-15 960; IRD: -552 per 10(6) person-years; 95% CI: -576 to -529 per 10(6) person-years; IRR: 0.78; 95% CI: 0.77-0.78). Hospitalizations for empyema, on the other hand, were more than expected (83 more; 95% CI: 37-128; IRD: 3 per 10(6) person-years; 95% CI: 1-5 per 10(6) person-years; IRR: 1.35; 95% CI: 1.14-1.59). Reductions in hospitalizations were observed for all ICD-10 pneumonia codes across all age groups. The increase in empyema hospitalizations was only significant among children aged 1 to 4 years.

CONCLUSION

The introduction of the PCV7 in Australia was associated with a substantial decrease in hospitalizations for childhood pneumonia and a small increase in hospitalizations for empyema.