Capsular Types and Antibiotic Susceptibility of Invasive Streptococcus pneumoniae Among Children in Sweden

Pneumococcal carriage in children and their household contacts six years after introduction of the 13-valent pneumococcal conjugate vaccine in England

Background

In April 2010, 13-valent pneumococcal conjugate vaccine (PCV13) replaced PCV7 in the infant immunisation schedule in England and Wales. Despite limited serotype replacement in invasive pneumococcal disease (IPD) during the first four post-PCV13 years, non-vaccine type (NVT) IPD increased substantially in 2014/15. We undertook a carriage study in 2015/16 to help understand the reasons for this increase.

Methods and findings

Families with a child aged <5 years attending a participating general practice in Gloucestershire or Hertfordshire were invited to provide nasopharyngeal swabs from all consenting members. Swabs from 650 individuals (293 under five, 73 five to twenty and 284 >twenty years) were cultured and serotyped for Streptococcus pneumoniae. Results were compared with those from three previous household studies conducted in the same populations between 2001 to 2013, and with the serotypes causing IPD to estimate case-carrier ratios (CCRs). Overall carriage prevalence did not differ between the four carriage studies with reductions in vaccine-type carriage offset by increases in NVT carriage. While no individual NVT serotype showed an increase in CCR from 2012/13, the composition of the serotypes comprising the NVT group differed such that the overall CCR of the NVT group had significantly increased since 2012/13. Carriage of two PCV13 serotypes, 3 and 19A, was found in 2015/16 (3/650 = 0.5% and 2/650 = 0.3% respectively) with no overall reduction in carriage prevalence of PCV13-7 serotypes since 2012/13, though 6C prevalence, a vaccine-related serotype, had reduced from 1.8% in 2012/13 to 2/648 (0.3%) in 2015/16, p = 0.013.

Conclusions

There was continuing evolution in carried NVTs six years after PCV13 introduction which, in addition to being vaccine-driven, could also reflect natural secular changes in certain NVTs. This poses challenges in predicting future trends in IPD. Elimination of carriage and disease due to serotypes 3 and 19A may not be achieved by PCV13.

Interim results of an ecological experiment - Conjugate vaccination against the pneumococcus and serotype replacement

Streptococcus pneumoniae has more than 95 serotypes, each of which presumably can cause sepsis, meningitis, pneumonia, and acute otitis media. Pneumococcal conjugate vaccines (PCV) targeted against a limited number of serotypes have nonetheless revealed an impressive impact on each manifestation of pneumococcal disease. At the same time, growing evidence of significant non-vaccine type (NVT) replacement disease following implementation of infant PCV programs has raised questions about the long-term viability of PCV immunization strategies and how to optimize PCV formulations. We discuss here theoretical and practical considerations regarding serotype replacement, and provide a snapshot of the most important NVT types seen to date after implementation of the 2 higher-valent PCVs.

Evolution of antimicrobial resistance and serotype distribution of Streptococcus pneumoniae isolated from children with invasive and noninvasive pneumococcal diseases in Algeria from 2005 to 2012

Pneumococcal infections are a major cause of morbidity and mortality in developing countries. The introduction of pneumococcal conjugate vaccines (PCVs) has dramatically reduced the incidence of pneumococcal diseases. PCVs are not currently being used in Algeria. We conducted a prospective study from 2005 to 2012 in Algeria to determine antimicrobial drug resistance and serotype distribution of Streptococcus pneumoniae from children with pneumococcal disease. Among 270 isolated strains from children, 97 (36%) were invasive disease; of these, 48% were not susceptible to penicillin and 53% not susceptible to erythromycin. A high rate of antimicrobial nonsusceptibility was observed in strains isolated from children with meningitis. The serotype distribution from pneumococci isolated from children with invasive infections was (by order of prevalence): 14, 1, 19F, 19A, 6B, 5, 3, 6A and 23F. Multidrug resistance was observed in serotypes 14, 19F, 19A and 6B. The vaccine coverage of serotypes isolated from children aged <5 years was 55.3% for PCV7, 71.1% for PCV10 and 86.8% for PCV13. Our results highlight the burden of pneumococcal disease in Algeria and the increasing S. pneumoniae antibiotic resistance. The current pneumococcal vaccines cover a high percentage of the circulating strains. Therefore, vaccination would reduce the incidence of pneumococcal disease in Algeria.

Current trend of pneumococcal serotypes distribution and antibiotic susceptibility pattern in Malaysian hospitals

From January 2008 to December 2009, 433 Streptococcus pneumoniae strains were examined to determine the serotype distribution and susceptibility to selected antibiotics. About 50% of them were invasive isolates. The strains were isolated from patients of all age groups and 33.55% were isolated from children below 5 years. The majority was isolated from blood (48.53%) and other sterile specimens (6.30%). Community acquired pneumonia (41.70%) is the most common diagnosis followed by sepsis (9.54%). Serotyping was done using Pneumotest Plus-Kit and antibiotic susceptibility pattern was determined by modified Kirby-Bauer disk diffusion method and measurement of minimum inhibitory concentration (MIC) using E-test strip. Ten most common serotypes were 19F (15.02%), 6B (10.62%), 19A (6.93%), 14 (6.70%), 1 (5.08%), 6A (5.08%), 23F (4.85%), 18C (3.93%), 3 (2.08%) and 5 (1.85%). Penicillin MIC ranged between ≤ 0.012-4 μg/ml with MIC₉₀ of 1 μg/ml. Penicillin resistant rate is 31.78%. The majority of penicillin less-susceptible strains belonged to serotype 19F followed by 19A and 6B. Based on the serotypes distribution 22 (44.00%), 28 (56.00%) and 39 (78.00%) of the invasive isolates from children ≤ 2 years were belonged to serotypes included in the PCV7, PCV10 and PCV13, respectively.

The epidemiology of pneumococcal infections--the Swedish experience

Pneumococcal infections are major contributors to morbidity and mortality world-wide and pose a major public health problem. Despite being a devastating pathogen pneumococci are common colonizers of the upper respiratory tract of healthy children. There is a need for more knowledge on the molecular epidemiology, and pathogenesis of pneumococcal infections to be able to find better strategies for prevention and treatment of these common infections. Here we discuss trends in the vaccine era of the epidemiology of pneumococcal carriage, invasive disease and antibiotic resistance development as well as present national epidemiology data from Sweden of invasive pneumococcal infections during 1987-2006.

10-valent pneumococcal nontypeable Haemophilus influenzae PD conjugate vaccine: Synflorix

The global burden of disease due to Streptococcus pneumoniae remains high. The licensed 7-valent pneumococcal conjugate vaccine (7vCRM, Prevenar/Prevnar) has successfully reduced invasive disease in the USA, but serotype coverage is incomplete and some evidence suggests that serotype replacement has occurred. Recently, a new 10-valent pneumococcal nontypeable Haemophilus influenzae (NTHi) protein D (PD) conjugate vaccine (PHiD-CV, Synflorix) has been licensed in more than 40 countries, including Europe, for the prevention of invasive disease and acute otitis media (AOM) due to pneumococcus in infants and children. PHiD-CV is immunogenic in infants when administered as a three-dose primary vaccination in a range of schedules and has a safety profile comparable to that of 7vCRM. Additional serotypes in PHiD-CV (1, 5 and 7F) increase overall serotype coverage and improve coverage in specific age groups and against specific disease syndromes. The use of the PD carrier, which provided protection against AOM caused by NTHi in a large efficacy trial testing a prototype of the final vaccine formulation, suggests that PHiD-CV will also provide some protection against AOM due to NTHi.

Antimicrobial susceptibility of invasive pneumococcal isolates from a region in south-west Sweden 1998–2001

Invasive disease caused by antibiotic resistant pneumococci is a worldwide problem. All invasive pneumococcal strains in an area of south-west Sweden with 1.7 million inhabitants were collected prospectively during 1998-2001. Minimum inhibitory concentrations (MICs) were determined by E-test and correlated to serotypes and clinical characteristics. Of 827 strains, 744 (90%) were susceptible (S) to all agents tested and 83 (10%) were indeterminate (I) or resistant (R) to at least 1 agent. 22 isolates (2.7%) were I to penicillin (MIC >0.06 to < or = 1.0 mg/l), but none were R (MIC >1.0 mg/l). Numbers and proportions of decreased susceptibility against other agents tested were as follows: erythromycin R: 30 (3.6%), clindamycin R: 6 (0.7%), tetracycline R: 16 (1.9%), moxifloxacin R: 1 (0.1%), cotrimoxazole I: 17 (2%) and R: 31(4%). Non-susceptibility to at least 1 agent was not correlated with age, clinical manifestation, underlying diseases and outcome. The serotype distribution differed between non-susceptible and susceptible strains. The serotypes in the 7-valent pneumococcal conjugate vaccine covered 42% of all infections and 73% of those caused by non-susceptible strains. In conclusion, the impact of antibiotic resistance in invasive pneumococcal disease remains limited in south-west Sweden.

Temporal trends of invasive Streptococcus pneumoniae serotypes and antimicrobial resistance patterns in Spain from 1979 to 2007

Temporal trends of serotypes from invasive pneumococcal disease (IPD) in Spain from 1979 to September 2007 under antibiotic and vaccine pressure were analyzed. A significant trend in pneumococcal conjugate 7-valent vaccine (PCV7) serotypes (except serotype 4) was found, whereby the prevalence increased from the early 1980s and decreased in the 2000s for all but serotype 23F, which began decreasing in the late 1980s. Among the major non-PCV7 serotypes, a significant decrease was observed for serotypes 1, 5, and 7F in the 1980s. From the late 1990s, serotypes 1, 5, 6A, 7F, and 19A increased significantly, while serotypes 3 and 8 showed similar but nonsignificant trends over time. The incidence of IPD cases was 10.7/100,000 for the period 1996 to 2006, with reporting coverage ranging from 18% to 43%. A significant decrease in IPD incidence due to PCV7 serotypes was observed, while the incidence of non-PCV7 serotypes increased, with the consequence that there was no clear pattern in the overall incidence of IPD. Penicillin nonsusceptibility was correlated with the proportion of PCV7 serotypes. Erythromycin nonsusceptibility increased in association with long-half-life macrolide consumption and then decreased in 2004 to 2007. The increase in PCV7 serotypes and antibiotic nonsusceptibility related to antibiotic consumption in the 1980s and 1990s was reversed in the 2000s, probably as a result of PCV7 immunization. The decrease in IPD incidence due to PCV7 serotypes was mirrored by an increase in that of non-PCV7 serotypes. The impact of various preventive/therapeutic strategies on pneumococcal evolution is serotype dependent, and the dynamics remain unpredictable.

Cost-effectiveness analysis of a universal vaccination programme with the 7-valent pneumococcal conjugate vaccine (PCV-7) in Sweden

The 7-valent pneumococcal conjugate vaccine (PCV-7) has proved to be highly effective against invasive pneumococcal disease and has also provided some protection against all-cause pneumonia and acute otitis media. The objective of this study was to evaluate the projected health benefits, costs and cost-effectiveness of vaccination with the 7-valent conjugated pneumococcal vaccine compared with no vaccination, in all infants in Sweden, taking herd immunity into account. A Markov model was used and a hypothetical birth cohort was simulated for a lifelong perspective. The results show that vaccination of 1 cohort could potentially prevent 9 cases of pneumococcal meningitis, 22 cases of pneumococcal septicaemia, 509 cases of hospitalized pneumonia, 7812 cases of acute otitis media, and 2.7 fatalities, among children 0-4 y of age and 6 episodes of pneumococcal meningitis and 167 cases of pneumococcal septicaemia among adults. The incremental cost per QALY and LY gained was estimated to Euro 29,200 and Euro 51,400, respectively. When herd immunity was accounted for, the cost per QALYand LY gained was estimated to Euro 5500 and Euro 6600, respectively. Thus, the health benefits of a national vaccination programmeme can be achieved within a 'moderate' or 'low' cost per QALY gained.

Pediatric parapneumonic empyema, Spain

Increased incidence is principally due to highly invasive nonvaccine serotypes of pneumococci, especially serotype 1.

Pediatric parapneumonic empyema (PPE) has been increasing in several countries including Spain. Streptococcus pneumoniae is a major PPE pathogen; however, antimicrobial pretreatment before pleural fluid (PF) sampling frequently results in negative diagnostic cultures, thus greatly underestimating the contribution of pneumococci, especially pneumococci susceptible to antimicrobial agents, to PPE. The study aim was to identify the serotypes and genotypes that cause PPE by using molecular diagnostics and relate these data to disease incidence and severity. A total of 208 children with PPE were prospectively enrolled; blood and PF samples were collected. Pneumococci were detected in 79% of culture-positive and 84% of culture-negative samples. All pneumococci were genotyped by multilocus sequence typing. Serotypes were determined for 111 PPE cases; 48% were serotype 1, of 3 major genotypes previously circulating in Spain. Variance in patient complication rates was statistically significant by serotype. The recent PPE increase is principally due to nonvaccine serotypes, especially the highly invasive serotype 1.

Age-stratified prevalences of pneumococcal-serotype-specific immunoglobulin G in England and their relationship to the serotype-specific incidence of invasive pneumococcal disease prior to the introduction of the pneumococcal 7-valent conjugate vaccine

Recent changes to the childhood immunization schedule in the United Kingdom have resulted in the inclusion of the 7-valent pneumococcal conjugate vaccine. However, the seroprevalence of pneumococcal antibodies in the population was unknown. To address this, we measured pneumococcal, age-specific immunoglobulin G (IgG) concentrations specific for nine serotypes by an assay run on the Bioplex platform, using 2,664 serum samples collected in England from 2000 to 2004. The lowest concentrations of IgG specific to all serotypes and the proportions of serotype-specific IgG concentrations of >/=0.35 microg/ml were observed in children aged <1 year. From 1 year on, there was a general increase in antibody levels with increasing age, and they remained high in adults. Maternal antibody was detected in young children aged <36 days but waned rapidly. Comparison of the age-specific seroprevalence of serotype-specific IgG to the serotype-specific incidence of invasive pneumococcal disease demonstrated a general inverse relationship for all age groups except the elderly. These data provide a baseline for natural immunity to the pneumococcal serotypes analyzed prior to the introduction of pneumococcal conjugate vaccine in the United Kingdom.

Immunogenicity and safety of pneumococcal 7-valent conjugate vaccine (diphtheria CRM(197) protein conjugate; Prevenar ) in Korean infants: differences that are found in Asian children

This study was conducted to determine the immunogenicity and safety of a 7-valent CRM197 protein conjugated pneumococcal vaccine (PCV7) in Korean infants immunized at 2, 4 and 6 months. A total of 202 infants were enrolled and 146 and 141 infants were, respectively, included in post-2nd dose and post-3rd dose immunogenicity evaluations conducted on a per protocol basis. After two and three PCV7 vaccinations, 63.0-98.0 and 97.2-100% of infants achieved an antibody level of >or=0.35microg/mL, respectively, with a lowest against serotype 6B. No vaccination-related serious adverse reactions were observed. Thus, PCV7 appears safe and highly immunogenic in Korean infants, and adopting two doses for a primary series could be a feasible option for facilitating vaccine coverage rate.

The roles of pneumococcal serotypes 1 and 5 in paediatric invasive disease

A small number of serotypes are responsible for most invasive pneumococcal disease in children worldwide. Serotypes 1 and 5 were among the first pneumococcal serotypes to be identified, reflecting their great prominence as causes of disease in the early part of the 20th century. In the antibiotic era, these serotypes persist as important causes of disease in children in most countries even though they, unlike some other common serotypes, remain sensitive to antimicrobial agents. These types also exhibit a high level of virulence, cause disease clusters or outbreaks, infect all age groups, and cause severe disease. Future vaccine formulations that protect against these types are important for developed and developing countries alike.

Serotypes of Streptococcus pneumoniae isolated from blood and cerebrospinal fluid related to vaccine serotypes and to clinical characteristics

Pneumococci isolated from blood and cerebrospinal fluid from 1998 to 2001 in 2 counties in south-west Sweden were serotyped with the capsular reaction test. Of the 836 strains, 353 (42%), 598 (72%) and 789 (94%) belonged to serotypes included in the 7- and 11-valent pneumococcal conjugate vaccines and in the 23-valent polysaccharide vaccine, respectively. The most common serotype was type 1 (119 isolates) followed in descending frequency by serotypes 7F, 9V, 14, 4 and 12F (90-49 isolates per serotype). The coverage rates of the 7- and 11-valent conjugate vaccines among 58 strains isolated from children and adolescents 0-19 y of age were 46% and 93%, respectively. A comparison of clinical characteristics of infections caused by different serotypes showed that types 1 and 7F were less commonly associated with severe underlying diseases, that patients infected with these serotypes were younger than the average and, thus, had a lower case-fatality rate.

Burden of paediatric invasive pneumococcal disease in Europe, 2005

Within the European Union (EU), documenting the burden of invasive pneumococcal disease (IPD) in infants and children is important for coordinating effective pneumococcal immunization policies. Our objective was to document the burden of IPD in countries of the EU plus Switzerland and Norway. European affiliates of Wyeth Vaccines made available recent epidemiological data on IPD from local disease surveillance programmes, including unpublished sources. Recent literature and websites were also searched to provide as wide a representation as possible. This included OVID and abstracts from a number of international meetings, dating from the year 2000. The reported rates of paediatric IPD per 100000 (age) ranged from a low of 1.7 (<2 years) to 4.2 (2-15 years) in Sweden to a high of 93.5 to 174 (<2 years) to 56.2 (<5 years) in Spain. The percentage of circulating serotypes causing IPD that are covered by 7-valent pneumococcal conjugate vaccine (PCV) IPD serotype coverage ranged from 60% to 80% for European children aged <2 years. Under reporting, differences in reporting methods, antibiotic prescribing and disparities in blood-culturing practices may explain the differences in reported disease incidence. Because of the excellent clinical efficacy of the PCV against IPD, national pneumococcal vaccination programmes in Europe have the potential to prevent much morbidity and mortality.

Epidemiologic features of invasive pneumococcal disease in Belgian children: passive surveillance is not enough

BACKGROUND

Reliable epidemiologic surveillance of infectious diseases is important for making rational choices for public health issues such as vaccination strategies. In Belgium, as in most European countries, surveillance relies on voluntary passive reporting from microbiology laboratories; therefore, reported incidence rates are probably inaccurate.

METHODS

We conducted national, active, laboratory-based and clinically based surveillance of invasive pneumococcal disease in young children.

RESULTS

During the study period, the incidences of invasive pneumococcal disease in children < 2 years of age (104.4 cases per 10(5) person-years and 16.1 cases per 10(5) person-years for invasive pneumococcal disease and meningitis, respectively) and in children 0 to 59 months of age (59.5 cases per 10(5) person-years for invasive pneumococcal disease and 7.7 cases per 10(5) person-years for meningitis) were twice those reported previously through the passive surveillance system. Overall, 67% of the Streptococcus pneumoniae strains isolated from children < 5 years of age belonged to 7-valent pneumococcal conjugate vaccine serotypes and 18% to vaccine-related serotypes (mainly serotype 19A). Erythromycin resistance was frequent, especially among children < 2 years of age (59%).

CONCLUSIONS

Under-reporting can explain the reported low incidence of invasive pneumococcal disease in countries (such as Belgium) that depend on a passive epidemiologic surveillance system, which could lead to erroneous choices in vaccination policies. There is a need for an active system of epidemiologic surveillance for vaccine-preventable diseases such as invasive pneumococcal disease, at the national or European level.

Streptococcus pneumoniae in western Europe: serotype distribution and incidence in children less than 2 years old

We did a systematic search and synthesis of evidence on the incidence of invasive pneumococcal disease, symptomatic disease, and circulating Streptococcus pneumoniae serotypes in western Europe. Using data from studies published between 1992 and 2005 we calculated a weighted mean invasive pneumococcal disease and pneumococcal meningitis incidence rate per 100,000 children aged 2 years or younger within 95% confidence intervals, together with the prevalence of S. pneumoniae serotypes and resistance to penicillin. Invasive pneumococcal disease incidence was 27.03 cases per 100,000 children under 2 years (95% CI 21.85-33.43) [corrected] Heptavalent conjugate vaccine serotypes account for 43.18-75.32% of isolates among people aged under 18 years of age. 11% of isolates in individuals aged under 18 years were penicillin resistant. The incidence of invasive pneumococcal disease appeared consistently lower in western European countries compared with studies from the USA. Thus the use of studies of vaccine effectiveness based on the US population may lead to an overestimation of the benefits of its introduction in Europe.

Immunogenicity and tolerability of a heptavalent pneumococcal conjugate vaccine administered at 3, 5 and 12 months of age

BACKGROUND

The recommended vaccination schedule for the pneumococcal conjugate vaccine (PCV) includes 4 immunizations, according to the national programs in the United States and some European countries. Other countries use a national schedule for routine vaccinations in early childhood that includes only 3 doses.

AIMS

The goals were to assess the immunogenicity and tolerability of PCV with a vaccination schedule that included 3 doses during the first 1 year of life (a 2+1 dose schedule) and to determine the immune responses to concomitantly administered Haemophilus influenzae type b (Hib) vaccine.

METHODS

A total of 101 healthy Swedish infants were enrolled in an open, nonrandomized, multicenter study. PCV was administered concomitantly with (at separate sites) a diphtheria-tetanus toxoids-acellular pertussis vaccine, inactivated polio vaccine and Hib conjugate vaccine combination at 3, 5 and 12 months of age. IgG antibody concentrations for the 7 serotypes included in the PCV and the Hib capsular polysaccharide in serum samples taken at 3, 6, 12 and 13 months were determined with enzyme immunoassays. Local and systemic reactions were monitored for 3 days after each immunization, and serious adverse reactions were monitored for the whole study period.

RESULTS

Two doses of PCV induced satisfactory antibody responses, with the exception of serotypes 6B and 23F. The third dose evoked strong responses for all serotypes, which suggests good immunologic priming with the primary series of 2 doses. The mean anti-Hib antibody concentrations were similar to those noted in earlier studies among Swedish children. The PCV was well tolerated.

CONCLUSION

The pneumococcal antibody concentrations at 13 months were comparable with those noted previously with the 4-dose schedule. The results suggest that the implementation of a 2+1 dose schedule for PCV should be considered.

Pneumococcal conjugate vaccines for preventing vaccine-type invasive pneumococcal disease and pneumonia with consolidation on x-ray in children under two years of age

BACKGROUND

Pneumonia, most commonly caused by Streptococcus pneumoniae (Pnc), is a major cause of morbidity and mortality among young children especially in developing countries. Recently, the prevalence of antibiotic-resistant Pnc has increased worldwide such that the effectiveness of preventive strategies, like the new pneumococcal conjugate vaccines (PCV) on rates of invasive pneumococcal disease (IPD) and pneumonia, needs to be evaluated.

OBJECTIVES

To determine the efficacy of PCV in reducing the incidence of IPD due to vaccine serotypes (VT) and x-ray confirmed pneumonia with consolidation of unspecified etiology in children who received PCV before 12 months of age.

SEARCH STRATEGY

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2004), MEDLINE (1990 to March 2004) and EMBASE (1990 to December 2003). Reference list of articles, and books of abstracts of relevant symposia, were hand searched. Researchers in the field were also contacted.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing PCV with placebo, or another vaccine, among children below two years with IPD and clinical/radiographic pneumonia as outcomes.

DATA COLLECTION AND ANALYSIS

Two reviewers independently identified eligible studies, assessed trial quality, and extracted data. Differences were resolved by discussion. The inverse variance method was used to pool effect sizes.

MAIN RESULTS

We identified four trials assessing the efficacy of PCV in reducing the incidence of IPD, two on x-ray confirmed pneumonia as outcome, and one on clinical pneumonia, with or without x-ray confirmation. Results from pooling HIV-1 negative children from the South African study with the other studies were as follows: the pooled vaccine efficacy (VE) for vaccine-type IPD was 88% (95% confidence interval (CI) 73% to 94%; fixed effect and random effects models), the effect measure was statistically significant (p <0.00001) and there was no heterogeneity (p = 0.77I2 0%); the pooled VE for all-serotype IPD was 66% (95% CI 46% to 79%; fixed effect model), the effect measure was statistically significant (p <0.00001) and there was no statistical heterogeneity (p = 0.09, I2 51%); the pooled VE for x-ray confirmed pneumonia was 22% (95% CI 11% to 31%; both fixed effect and random effects models) and there was no statistical heterogeneity (p = 0.80, I2 0%). Analyses that included all the children in the South African study (HIV-1 negative and HIV-1 positive children) and pooled with data from the other studies gave very similar results.

REVIEWERS' CONCLUSIONS

PCV is effective in reducing the incidence of IPD from all serotypes but exerts a greater effect in reducing VT IPD. Although PCV is also effective in reducing the incidence of x-ray confirmed pneumonia, there are still uncertainties about the definition of this outcome. Additional randomised controlled trials are currently in progress.