Conjugate pneumococcal vaccine and antibiotic-resistant Streptococcus pneumoniae: herd immunity and reduction of otitis morbidity

Bacterial Spectrum of Spontaneously Ruptured Otitis Media in a 7-Year, Longitudinal, Multicenter, Epidemiological Cross-Sectional Study in Germany

We analyzed middle ear fluid (MEF) and nasopharyngeal swabs (NPS) from spontaneously ruptured acute otitis media (AOM) cases occurring in children under 5 years in Germany. The aim of the study was the assessment of disease burden and bacterial etiology in the era of routine pneumococcal vaccination. Furthermore, we aimed to compare isolates from MEF with isolates from NPS and to analyze the Streptococcus pneumoniae serotype distribution. We analyzed MEF and NPS samples in children 2 months to 5 years for vaccination status, frequency of bacterial strains, serotype/emm-type distribution of S. pneumoniae, Haemophilus influenzae, and Streptococcus pyogenes; and intraindividual correlation between MEF and NPS. From 2008 to 2014, MEF samples were collected from 2,138 subjects of which 2,001 (93.6%) also provided an NPS sample. In 851 of 2,138 MEF samples (39.8%), we identified organisms with confirmed pathogenic potential—S. pyogenes: 315 (14.7%), S. pneumoniae: 170 (8.0%), Staphylococcus aureus: 168 (7.9%), H. influenzae: 133 (6.2%), and Moraxella catarrhalis. Among NPS samples, 1,018 (50.9%) contained S. pneumoniae, 775 (38.7%) H. influenzae, 648 (32.4%) M. catarrhalis, and 344 (17.2%) S. pyogenes. Over the seven study years, the number of AOM patients steadily decreased, while the recruiting base remained constant. S. pneumoniae MEF isolates decreased by 86%, with serotype 3 being the most prevalent (25.7–42.9%). PCV13-non-PCV7-non-3 serotypes reduced to 0%. Among NPS, PCV7 serotypes decreased from 14.1 to 3.7%, PCV10: 17.6 to 3.7%, and PCV13: 55.3 to 25.7%. PCV13-non-PCV7-non-3 serotypes increased in the first 3 years of the study (17.1–22.9%), then decreased to 4.6% in year 7. Non-typeable H. influenzae reduced from 87.1 to 41.7% in MEF and from 91.4 to 54.2% in NPS. MEF and NPS isolates from the same subject were identical for 91.9% of S. pneumoniae, 99.0% of S. pyogenes, and 83.3% of H. influenzae. Among PCV7-vaccinated children, 5.6% had a PCV7 vaccine type in the MEF sample, and among PCV13-vaccinated children, 51.7% had a PCV13 serotype. Among non-vaccinated children, the percentages were 14.8 and 70.4. Pneumococcal conjugate vaccination has impacted the prevalence and etiology of spontaneously ruptured otitis media among children in Germany. Overall case numbers and pneumococcal vaccine type cases have strongly decreased.

Risk factors associated with Streptococcus pneumonia carriage in children under five years old with acute respiratory infection in Niger

Introduction

Streptococcus pneumonia is a leading cause of bacterial pneumonia, meningitis and sepsis in children, and pneumococcal carriage is an important source of horizontal spread of these pathogens within the community.

Methods

A questionnaire was addressed to parents for the collection of sociodemographic and medical information. Nasopharyngeal swabbing was processed using a molecular method. We used logistic regression models to examine independent associations between pneumococcal carriage and potential risk factors. All associations with a p-value of < 0.25 in the bivariate regression analyses were subsequently entered in the multivariate regression model.

Results

A total of 637 children aged 1 to 59 months admitted for acute respiratory infection were included. The rate of respiratory virus carriage was 76%, whereas that of bacteria was 47% and that of bacteria-virus co-colonization was 42%. A bivariate analysis showed that carriage was not related to gender, father's or mother's education level, father's occupation, type of housing or lighting, or passive exposure to cigarette smoking in the house. It was also not linked to complete vaccination with PCV-13 or PPSV-23 and antibiotic treatment prior to hospitalization. A multivariate analysis showed that carriage was related to age greater than 3 months, maternal occupation, house flooring type, and co-colonization of another bacterium and virus.

Conclusion

These results can be helpful to understand the dynamics of pneumococcal nasopharyngeal colonization; they confirm the interest of vaccinating infants before the age of 3 months with appropriate vaccine to prevent spread nasopharyngeal colonization and pneumococcal diseases in children.

Bacterial spectrum of spontaneously ruptured otitis media in the era of pneumococcal conjugate vaccination in Germany

Otitis media is a common pediatric disease and the main reason for antibiotic prescription in children. Before implementation of routine childhood pneumococcal vaccination in Germany, serotypes contained in the seven-valent pneumococcal conjugate vaccine (PCV) were among the most frequent pneumococcal serotypes responsible for acute otitis media (AOM). This report describes the first 3 years of a prospective, multicenter, epidemiological cross-sectional study examining the bacteriology of middle ear fluids (MEF) and nasopharyngeal swabs (NPS) of children 2 months to 5 years of age with spontaneously perforated AOM in the era of routine pneumococcal vaccination. MEF was obtained from 963 subjects; NPS from 877. Reported case numbers steeply decreased over the three study years even though the recruiting base remained the same. Among subjects with relevant bacterial growth in their MEF swabs, 113 (11.7%) had Streptococcus pyogenes, 97 (10.1%) Staphylococcus aureus, 88 (9.1%) Streptococcus pneumoniae, 63 (6.5%) Haemophilus influenzae, and 8 (0.8%) Moraxella catarrhalis. S. pneumoniae isolates decreased from 41 (9.3%) in year 1 to 12 (5.7%) in year 3 (p = 0.128). PCV7 serotypes accounted for only 7.9% (n = 7) of isolated pneumococci. Of the 877 subjects with NPS cultures, 465 (53.0%) carried S. pneumoniae, 314 (35.8%) H. influenzae, 292 (33.3%) M. catarrhalis, and 110 (12.5%) S. pyogenes; 79.4% (n = 765) of the children were vaccinated with at least one dose of PCV. Carriage of pneumococci was slightly lower in vaccinated (47.8%) than in unvaccinated (52.7%) children (p = 0.254). PCV7 serotypes were carried by 9.6% of unvaccinated children but by only 4.2% of vaccinated children, resulting in a 56.3% vaccine effectiveness.

CONCLUSIONS

Following universal PCV7 immunization, a clear epidemiological impact of pneumococcal conjugate vaccination was observed as PCV7 serotypes have almost disappeared among AOM.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Approximately 450,000 children worldwide die of pneumococcal infections each year. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but do not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 July 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing, or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We contacted study authors for additional information.

MAIN RESULTS

Seven trials were included, but only six trials (919 participants) contributed data. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (risk ratio (RR) 0.66; 95% confidence interval (CI) 0.30 to 1.46; two trials, 241 pregnancies, low quality evidence). Although the data suggest an effect in reducing pneumococcal colonization in infants by 16 months of age (average RR 0.33; 95% CI 0.11 to 0.98; one trial, 56 pregnancies), there was no evidence of this effect in infants at two to three months of age (average RR 1.13; 95% CI 0.46 to 2.78; two trials, 146 pregnancies, low quality evidence) or by six to seven months of age (average RR 0.67, 95% CI 0.22 to 2.08; two trials, 148 pregnancies, low quality evidence). None of the trials included in this review reported neonatal death as a result of pneumococcal infection.Neonatal antibody levels were reported as geometric mean and 95% CI. There were inconsistent results between studies. Two studies showed significantly higher immunoglobulin G (IgG) levels in cord blood in the pneumococcal vaccine group when compared with the control group for all serotypes. In contrast, another trial showed no difference in neonatal antibody levels between the pneumococcal vaccine group and the control group.Maternal antibody levels were also reported as geometric mean and 95% CI. One study showed significantly higher IgG levels in maternal serum in women immunized with pneumococcal vaccine when compared with control vaccine regardless of any serotypes. Another study showed significantly higher maternal antibody levels only for serotype 14, but no evidence of an effect for other serotypes.The percentage of women with seroprotection was measured in one trial at delivery and at 12 months post-delivery. At delivery, results favored the intervention group for serotype 6 (RR 1.49, 95% CI 1.31 to 1.69), serotype 14 (RR 1.40, 95% CI 1.25 to 1.56) and serotype 19 (RR 2.29, 95% CI 1.89 to 2.76). There were no group differences seen at 12 months post-delivery for serotypes 6 or 14 (RR 1.06, 95% CI 1.00 to 1.12 and RR 1.06, 95% CI 0.98 to 1.15, respectively), but results favored the intervention group for serotype 19 (RR 1.59, 95% CI 1.37 to 1.85).No significant difference for tenderness at the injection site between women who received pneumococcal vaccine and those who received control vaccine (average RR 3.20; 95% CI 0.32 to 31.54; two trials, 130 women).The overall quality of evidence is low for primary outcomes. Most outcomes had wide confidence intervals crossing the line of no effect, and most of the included trials had small numbers of participants and few events which led to downgrading evidence for imprecision of findings.

AUTHORS' CONCLUSIONS

There is insufficient evidence to assess whether pneumococcal vaccination during pregnancy could reduce infant infections.

ASHP therapeutic position statement on strategies for identifying and preventing pneumococcal resistance

The incidence of MDRSP continues to increase, causing significant morbidity and mortality. Health care providers should seize the opportunity to promote the judicious use of antimicrobials and vaccinate patients with the pneumococcal vaccines as a means to lessen this significant health problem. Pharmacists are poised to play a key role in patient care by assessing for the need and administering vaccines in compliance with the current guidelines. A pharmacist should have a key role on the antimicrobial stewardship team.

Impact of 13-valent pneumococcal conjugate vaccine on otitis media bacteriology

OBJECTIVES

To determine the microbiology of otitis media (OM) since the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) in February 2010.

METHODS

Middle ear effusion from a pediatric Otolaryngology population undergoing pressure equalization tube (PET) placement was obtained and sent for aerobic culture and antibiotic susceptibility testing between August 2012 and April 2013. Vaccination records were obtained and statistical analysis was completed.

RESULTS

During the 8-month period, 236 ears were evaluated, and of those 39 ears were found to have positive cultures. The single nonvaccine Streptococcus pneumoniae (serotype 16) isolate was obtained from a PCV7-only vaccinated patient and was penicillin susceptible. The three most common isolates were Staphylococcus coagulase negative (57%), Haemophilus influenzae (17%), and Moraxella catarrhalis (7%).

CONCLUSIONS

This study is the first to assess the bacteriology of OM in a pediatric population undergoing PET placement in the immediate post-PCV13 era. Our study is limited by sample size; however, the lack of S. pneumoniae cultures indicates that PCV13 has had a significant impact on pneumococcal infections during these initial years following licensure.

Nasopharyngeal carriage of individual Streptococcus pneumoniae serotypes during pediatric radiologically confirmed community acquired pneumonia following PCV7 introduction in Switzerland

BACKGROUND

Community-acquired pneumonia (CAP) is a serious cause of morbidity among children in developed countries. The real impact of 7-valent pneumococcal conjugate vaccine (PCV7) on pneumococcal pneumonia is difficult to assess accurately.

METHODS

Children aged ≤16 years with clinical and radiological pneumonia were enrolled in a multicenter prospective study. Children aged ≤16 years admitted for a minor elective surgery was recruited as controls. Nasopharyngeal samples for PCR serotyping of S. pneumoniae were obtained in both groups. Informations on age, gender, PCV7 vaccination status, day care/school attendance, siblings, tobacco exposure were collected.

RESULTS

In children with CAP (n=236), 54% of the nasopharyngeal swabs were PCR-positive for S. pneumoniae compared to 32% in controls (n=105) (p=0.003). Serotype 19A was the most common pneumococcal serotype carried in children with CAP (13%) and in controls (15%). Most common serotypes were non-vaccine types (39.4% for CAP and 47.1% for controls) and serotypes included only in PCV13 (32.3% for CAP and 23.5% for controls). There was no significant difference in vaccine serotype distribution between the two groups. In fully vaccinated children with CAP, the proportion of serotypes carried only in PCV13 was higher (51.4%) than in partially vaccinated or non vaccinated children (27.6% and 28.6% respectively, p=0.037).

CONCLUSIONS

Two to 4 years following introduction of PCV7, predominant S. pneumoniae serotypes carried in children with CAP were non PCV7 serotypes, and the 6 new serotypes included in PCV13 accounted for 51.4% of carried serotypes in fully vaccinated children.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Each year at least one million children worldwide die of pneumococcal infections. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but does not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2011) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, methodological quality and extracted data using a data collection form. Data were checked for accuracy. We contacted study authors for additional information.

MAIN RESULTS

Seven trials were included, but only five trials (579 participants) contributed data. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (risk ratio (RR) 0.66; 95% confidence interval (CI) 0.30 to 1.46; two trials, 241 pregnancies). Although the data suggest an effect in reducing pneumococcal colonization in infants by 16 months of age (RR 0.33; 95% CI 0.11 to 0.98; one trial, 56 pregnancies), there was no evidence of this effect in infants at two to three months of age (RR 1.13; 95% CI 0.46 to 2.78; two trials, 146 pregnancies) or by six to seven months of age (RR 0.66; 95% CI 0.20 to 2.17; two trials, 144 pregnancies). No significant difference for tenderness at the injection site between women who received pneumococcal vaccine and those who received control vaccine (RR 3.20; 95% CI 0.32 to 31.54; two trials, 130 women).

AUTHORS' CONCLUSIONS

There is insufficient evidence to assess whether pneumococcal vaccination during pregnancy could reduce infant infections.

Can mucosal adjuvants contribute to the induction of immunological memory induced via unconjugated T-cell-independent antigens?

Vaccination remains the most cost-effective method for preventing infectious diseases. Key to vaccine design is the development of immunological memory, which is an essential property of the adaptive immune system. Bacterial polysaccharide conjugate vaccines are the gold standard currently used to confer protection of the host by inducing humoral immune responses against T-cell-independent antigens. Conjugate vaccines are effective, but we propose that local mucosal immune responses are likely to also play an important role in inducing immunity, and they have been less explored than systemic and adaptive immune responses. Adjuvants have been used to improve the immune response to vaccine antigens, however, no mucosal adjuvant has been licensed for human use. Here we describe the recent progress in the use of mucosal adjuvants to achieve significant immune responses against T-cell-independent antigens. We also introduce the idea that studying the mechanisms that induce cell sub-populations with strong immunological memory may facilitate the design of novel vaccine formulations, in particular in cases of B-cell unresponsiveness to thymus-independent stimuli.

Effect of the pneumococcal conjugate vaccine on pneumococcal carriage in Turkish children

BACKGROUND

  The aim of our study was to evaluate the effect of the seven-valent pneumococcal conjugate vaccine which has recently been included in the national immunization schedule on the nasopharyngeal carriage of Streptococcus pneumoniae in a group of healthy Turkish children. This is the first study determining the efficacy of this vaccine in Turkey.

METHODS

  One hundred and thirty-eight children who had completed their pneumococcal vaccination series and 109 unvaccinated control subjects aged 12-59 months were included in the study between October 2007 and April 2008. A single nasopharyngeal swab sample was obtained from each subject.

RESULTS

  S. pneumoniae was isolated in 32 (12.9%) of 247 subjects. No significant differences were detected in pneumococcal carriage rate between the vaccinees and controls (10.1% vs 16.5%). Prevalence of vaccine type (VT) carriage was statistically lower in the vaccinated group than the controls while non-vaccine type carriage (NVT) was similar. Most frequently isolated vaccine serotype was 23F in the vaccinated group and 19F in the non-vaccinated group. Of the isolated S. pneumoniae, 13.3% were penicillin susceptible and 86.7% were non-susceptible. Vaccinees and controls did not differ statistically with respect to carriage rate of penicillin-resistant S. pneumoniae. All the pneumococcal isolates were susceptible to ceftriaxone, vancomycin, rifampicin and quinolones.

CONCLUSION

  Seven-valent conjugate vaccine induces long-term protection against carriage of VT S. pneumoniae in Turkish children. The ability of the conjugate vaccine to reduce transmission of antibiotic resistant S. pneumoniae may be possible if its introduction is coupled with a reduction in inappropriate use of antibiotics.

Pneumococcal conjugate vaccines in the prevention of childhood pneumonia

Lower respiratory tract infections are among the most important causes of childhood mortality worldwide, more than 2 million children die due to pneumonia every year. A number of infections caused by the main pathogens related to pneumonia can be prevented through vaccination ( S. pneumoniae, H. influenzae type-b, morbilli, pertussis, influenza). In the last decade, after the introduction of the 7-valent pneumococcal conjugated vaccine (PCV), the epidemiological background of childhood pneumonia has changed. Recently, several studies have been performed to collect data and evidences about the efficacy of PCV against noninvasive pneumococcal diseases (e.g. pneumonia, otitis media). These investigations showed 10-50% decrease of all pneumonia cases, 10-30% decrease of radiologically diagnosed pneumonia, and 50-70% decrease of the incidence of pneumococcal pneumonia in children. The aim of this review was to determine the role of the PCV in the prevention of childhood pneumonia according to the medical literature, and to summarize the efforts of global organizations (WHO, UNICEF, GAVI) in the fight against pneumonia in children.

Serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae strains isolated from middle ear fluids of children aged 0–24 months with acute otitis media

Az akut otitis media a két éven aluli korcsoport egyik leggyakoribb betegsége, amelynek legfőbb bakteriális kórokozója a Streptococcus pneumoniae . A jelenleg elérhető, hét szerotípus elleni védelmet adó konjugált pneumococcusvakcina világszerte jelentős hatással van az otitis media, különösen a vakcinában megtalálható hét szerotípusba tartozó pneumococcusok okozta otitis media előfordulására. Az oltás hatékonysága az adott régióban észlelt otopatogén pneumococcus törzsek szerotípus-megoszlásától függ. A vizsgálat célja: Kétévesnél fiatalabb gyermekekben középfülgyulladást okozó S. pneumoniae törzsek szerotípusának és antibiotikum-érzékenységének meghatározása, és ezek összehasonlítása a nemzetközi adatokkal. Betegek és módszerek: 2002 és 2005 között 10 budapesti gyermekgyógyászati intézményben megjelent, 0–24 hónapos korú, otitis media acutában szenvedő gyermek dobüregi váladékából 73 S. pneumoniae törzset izoláltunk, amelyeket a Fővárosi Szent László Kórház Mikrobiológiai Laboratóriumában identifikáltuk és Quellung-reakció segítségével szerotipizáltuk. Az antibiotikum-érzékenységi vizsgálatokat a laboratórium a Magyar Mikrobiológiai Társaság által elfogadott standard módszerek alapján végezte és értékelte. Eredmények: A 73 izolált S. pneumoniae törzs 14 szerotípust reprezentált. A 14 (13,7%), a 19F (13,7%), a 6B (13,7%), a 23A (11%) és a 3 (9,6%) szerotípusok voltak a leggyakoribbak. A törzsek 63%-a tartozott a hét szerotípus ellen védelmet nyújtó konjugált vakcinában megtalálható szerotípusba. A penicillinre mérsékelten érzékeny törzsek aránya 41% volt, e törzsek 90%-a a vakcina szerotípusaiba tartozott. Penicillinrezisztenciát nem észleltünk. A leginkább rezisztens törzsek a 9V, 14, 19F szerotípusokba tartoztak. Következtetés: Az otopatogén S. pneumoniae törzsek szerotípus-megoszlása a hét szerotípus ellen védelmet adó konjugált pneumococcusvakcináció szempontjából az egyéb régiókban megismerteknek megfelel. Ennek alapján az oltás hatása az otitis media előfordulására a külföldi tanulmányokban igazoltakhoz hasonló lehet majd Magyarországon is.

Streptococcus Pneumonia Serotypes in Newly Developed State of Qatar: Consideration for Conjugate Vaccine

Objectives: The objective of the study was to determine prevalent pneumococcal serotypes causing infections in different age groups, their susceptibility to fi-lactams and macrolides and whether these serotypes are covered by the conjugated pneumococcal vaccines.

Methods: Streptococcus pneumonia strains isolated from different patients at Hamad Medical Corporation, Microbiology Laboratory between September 1999 and July 2000 were sent to Statum Serum Institute in Denmark for serotyping. The strains were tested for their susceptibility to penicillin, ceftriaxone and erythromycin by Vitek 2 machine (bioMerieux, France) at Hamad Medical Corporation, Microbiology Laboratory.

Results: Predominant serotypes in children <  2 years were: 6A, 6B, 9V, 11 A, 14,19A, 19F and 23 F, predominant serotypes in children between 2-7years were: 3, 6B, 15B, 19A, 19F and 23F, while predominant serotypes in adults were: 3, 8, 9V, 14,15B, 20 and 22F. In children less than 2 years, the 7-valent and 9-valent conjugate vaccines covered 52% of serotypes. 33% of strains were moderately resistant to penicillin, 27% showed high-level resistance to penicillin, 30% resistant to erythromycin and 2% resistant to ceftrixone.

Conclusion: The 7-valent and 9-valent vaccines offer similar coverage of serotypes in children less than 2 years while the 11-valent vaccines offers 55% coverage. This difference is not statistically significant. Resistance to penicillin was high which leaves ceftriaxone as the drug of choice for empirical treatment of invasive pneumococcal diseases.

Bacterial meningitis: the impact of vaccination

Acute bacterial meningitis remains an important cause of morbidity and mortality in children. Children <2 years of age are particularly susceptible to infection with encapsulated bacteria due to their immature response to polysaccharide antigens. Conjugate vaccines, which induce T cell memory, can provide immunological protection for these children. The Haemophilus influenzae type b (Hib) conjugate vaccine was the first such vaccine to become available. The efficacy of the vaccine has been quoted as being 98%. Its introduction was followed by a dramatic decrease in the incidence of all invasive Hib disease, including meningitis. This reduction was in part due to the ability of these vaccines to reduce nasopharyngeal carriage of the organism and thereby induce herd immunity. Different Hib vaccines use a variety of protein carriers and differ in their immunogenicity and efficacy. The most suitable vaccine needs to be determined according to the local epidemiology of Hib disease. Commercial combination vaccines may lead to lower antibody levels. A recent increase in the incidence of Hib disease in the UK highlights the importance of continued surveillance and the need for booster vaccinations to ensure continued protection. Conjugate vaccines to Streptococcus pneumoniae and Neisseria meningitidis have been developed. The introduction of a pneumococcal conjugate vaccine in the US has led to a decrease in the rate of infection by nearly 60% in children <5 years of age. A reduction in pneumococcal carriage may also modify disease epidemiology. The UK introduced the conjugate meningococcal C vaccine into its infant schedule with a corresponding reduction in N. meningitidis group C disease. A recent decrease in the effectiveness of the vaccine, however, suggests a booster may be necessary in the future. Our present understanding of the immunology of conjugate vaccines is far from complete. Developed countries have introduced conjugate vaccines into their immunisation schedules to prevent bacterial meningitis; however, their high cost precludes their use in many developing countries. Progress needs to be made in order to get these highly effective vaccines to those areas that need them.

Reduction of frequent otitis media and pressure-equalizing tube insertions in children after introduction of pneumococcal conjugate vaccine

OBJECTIVE

Streptococcus pneumoniae is an important cause of otitis media in children. In this study we estimated the effect of routine childhood immunization with heptavalent pneumococcal conjugate vaccine on frequent otitis media (3 episodes in 6 months or 4 episodes in 1 year) and pressure-equalizing tube insertions.

PATIENTS AND METHODS

The study population included all children who were enrolled at birth in TennCare or selected upstate New York commercial insurance plans as of July 1998 and continuously followed until 5 years old, loss of health plan enrollment, study outcome, or end of the study. We compared the risk of developing frequent otitis media or having pressure-equalizing tube insertion for 4 birth cohorts (1998-1999, 1999-2000, 2000-2001, and 2001-2002) by using Cox regression analysis. We used data from the National Immunization Survey to estimate the heptavalent pneumococcal conjugate vaccine uptake for children in these 4 birth cohorts in Tennessee and New York.

RESULTS

The proportion of children in Tennessee and New York who received at least 3 doses of heptavalent pneumococcal conjugate vaccine by 2 years of age increased from < or = 1% for the 1998-1999 birth cohort to approximately 75% for the 2000-2001 birth cohort. By age 2 years, 29% of Tennessee and New York children born in 2000-2001 had developed frequent otitis media, and 6% of each of these birth cohorts had pressure-equalizing tubes inserted. Comparing the 2000-2001 birth cohort to the 1998-1999 birth cohort, frequent otitis media declined by 17% and 28%, and pressure-equalizing tube insertions declined by 16% and 23% for Tennessee and New York children, respectively. For the 2000-2001 to the 2001-2002 birth cohort, frequent otitis media and pressure-equalizing tubes remained stable in New York but increased in Tennessee.

CONCLUSIONS

After heptavalent pneumococcal conjugate vaccine introduction, children were less likely to develop frequent otitis media or have pressure-equalizing tube insertions.

The Prevalence of Colonization with Drug-Resistant Pneumococci among Adult Workers in Children's Daycare

We conducted a study to determine if employment at a children's daycare facility increases an adult's risk of carrying Streptococcus pneumoniae in general and antibiotic-resistant S pneumoniae in particular. From January through March 2003, we obtained nasopharyngeal and oropharyngeal specimens from 63 adult workers at 6 daycare facilities and 65 similarly aged controls; all but 2 controls were nonclinical employees at our tertiary care center. Culture and sensitivity data were obtained from all specimens, and written questionnaires were used to gather information on each daycare worker, control, and daycare center. The vaccination records of children at 5 of the 6 daycare centers were reviewed. Odds ratios with 95% confidence intervals were calculated to compare the rates of colonization with S pneumoniae in the daycare workers and controls. Multinomial logistic regression analysis was used to compare different daycare centers and to identify risk factors for S pneumoniae carriage. Analysis of the results revealed that the prevalence of S pneumoniae colonization among daycare workers (3/63 [4.76%]) and controls (3/65 [4.62%]) was nearly identical. Whereas no S pneumoniae isolate from a daycare worker displayed multiple drug resistance, all 3 isolates from the controls did; however, this difference was not statistically significant. We conclude that employment at a children's daycare facility in our community did not increase an adult's risk of carrying S pneumoniae. In fact, daycare workers may be even less likely to carry antibiotic-resistant S pneumoniae because of the widespread and successful use of the heptavalent pneumococcal vaccine in young children.

Upgrading antibiotic use within a class: tradeoff between resistance and treatment success

Increasing resistance to antibiotics creates the need for prudent antibiotic use. When resistance to various antibiotics within a class is driven by stepwise accumulation of mutations, a dilemma may exist in regard to replacing an antibiotic that is losing effectiveness due to resistance with a new drug within the same class. Such replacement may enhance treatment success in the short term but promote the spread of highly resistant strains. We used mathematical models to quantify the tradeoff between minimizing treatment failures (by switching early) and minimizing the proliferation of the highly resistant strain (by delaying the switch). Numerical simulations were applied to investigate the cumulative prevalence of the highly resistant strain (Resistance) and the cumulative number of treatment failures (Failure) that resulted from following different antibiotic use policies. Whereas never switching to the new drug always minimizes Resistance and maximizes Failure, immediate switching usually maximizes Resistance and minimizes Failure. Thus, in most circumstances, there is a strict tradeoff in which early use of the new drug enhances treatment effectiveness while hastening the rise of high-level resistance. This tradeoff is most acute when acquired resistance is rare and the highly resistant strain is readily transmissible. However, exceptions occur when use of the new drug frequently leads to acquired resistance and when the highly resistant strain has substantial "fitness cost"; these circumstances tend to favor an immediate switch. We discuss the implications of these considerations in regard to antibiotic choices for Streptococcus pneumoniae.

Pneumococcal vaccination during pregnancy for preventing infant infection

BACKGROUND

Each year at least one million children worldwide die of pneumococcal infections. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but does not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection.

OBJECTIVES

To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (June 2004), CENTRAL (The Cochrane Library, Issue 2, 2004), MEDLINE (January 1966 to June 2004), EMBASE (January 1985 to June 2004), and reference lists of articles.

SELECTION CRITERIA

Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing or with another vaccine to prevent infant infections.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed methodological quality and extracted data using a data collection form. Study authors were contacted for additional information.

MAIN RESULTS

Three trials (280 participants) were included. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (one trial, 149 pregnancies, relative risk (RR) 0.51; 95% confidence interval (CI) 0.18 to 1.41). Although the data suggest an effect in reducing pneumococcal colonisation in infants by 16 months of age (one trial, 56 pregnancies, RR 0.33; 95% CI 0.11 to 0.98), there was no evidence of this effect in infants at two months of age (RR 0.28; 95% CI 0.02 to 5.11) or by seven months of age (RR 0.32; 95% CI 0.08 to 1.29).

AUTHORS' CONCLUSIONS

There is insufficient evidence to support whether pneumococcal vaccination during pregnancy could reduce infant infections.

Dynamics of pneumococcal carriage among healthy Icelandic children attending day-care centres

Invasive pneumococcal disease and antimicrobial (AM) resistance in pneumococci are important public health concerns. With the advent of new pneumococcal vaccines, information on serotype prevalence and their temporal fluctuations is important. Information on AM use and consent for participation was obtained by a questionnaire to parents of children at 5 day-care centres in Reykjavik from 1992 to 1999, and nasopharyngeal swabs were cultured selectively for pneumococci. The pneumococci were serotyped and pulsed field gel electrophoresis used to determine clonality. Of 1228 nasopharyngeal swabs, 640 (52.1%) yielded pneumococci of which 89 (13.9%) had decreased susceptibility to penicillin and 1 was resistant. Children receiving AMs during the month preceding nasopharyngeal sampling and children attending a day-care centre where AM use was high were significantly more likely to carry penicillin non-susceptible isolates. Serotypes 6A, 6B and 23F were most common (48%), and 74% of serotyped isolates belonged to 1 of the 7 most common serotypes. Almost all penicillin non-susceptible isolates were of serotype 6B or 19A. Serotype prevalence fluctuated markedly between y. In conclusion, there was significant variation in serotype prevalence between y, and only 51% of the pneumococci belonged to serotypes covered by the current 7-valent conjugated vaccine.

The Epidemiology of Childhood Pneumococcal Disease in the United States in the Era of Conjugate Vaccine Use

In 2000, a heptavalent pneumococcal conjugate vaccine was licensed and included in the schedule of routine childhood immunizations in the United States. The vaccine contains the serotypes most commonly associated with invasive and noninvasive pneumococcal infection in children and the serotypes most commonly expressing antibiotic resistance. Since the introduction of the vaccine, the incidence of invasive pneumococcal disease has declined dramatically in the United States, particularly among children younger than 2 years of age. The incidences of pneumonia and acute otitis media also have declined, but less substantially. Several factors may blunt the future effectiveness of the vaccine, however, particularly the emergence of noninvaccine pneumococcal serotypes and the propensity for pathogenic pneumococci to switch their capsular types, evading vaccine-conferred immunity.

Acquisition of Streptococcus pneumoniae and nonspecific morbidity in infants and their families: a cohort study

BACKGROUND

Most children are believed to acquire Streptococcus pneumoniae asymptomatically, with only a few developing overt S. pneumoniae disease. This study investigates the relationship between acquisition of S. pneumoniae and mild nonspecific infection leading to general practitioner (GP) consultation.

METHODS

A prospective birth cohort study of 213 infants assessed at home 9 times during 24 weeks by nasopharyngeal swab and parental interview was conducted.

RESULTS

All positive S. pneumoniae swabs (including acquisition and carriage) were significantly associated with GP consultations for infection by the study infant compared with infants with negative swabs [odds ratio (OR), 1.6; 95% confidence interval (CI) 1.1-2.2; P = 0.005]. There was a stronger association with S. pneumoniae acquisition alone (OR 2.1; 95% CI 1.3-3.4; P = 0.001) than with carriage only (OR 1.4; 95% CI 0.9-2.0; P = 0.1). Multivariate analysis confirmed that S. pneumoniae acquisition by the study subject was independently associated with GP consultations: adjusted hazard ratio, 1.8 (95% CI 1.1-2.9); P = 0.02. A similar and independent association was found between S. pneumoniae acquisition by the study subject, and GP consultations for infection by the family (adjusted hazard ratio, 1.8; 95% CI 1.1-2.8; P = 0.01).

CONCLUSION

Acquisition of S. pneumoniae by the study infant was significantly associated with GP consultations for infection by the infant or family.

Short-Course Antimicrobial Therapy for Community-Acquired Pneumonia

Management of community-acquired pneumonia (CAP) remains surprisingly controversial. Optimal duration of antimicrobial therapy reflects one of the open questions due to the lack of sufficient randomized clinical trial data. Recently, there have been efforts to rationalize antimicrobial therapy of this disease. Trials addressing the issue of short-course antimicrobial therapy for CAP have revealed no adverse outcomes with a treatment duration of 5 days when compared with conventional courses of 7-10 days. There is accumulating evidence that a shorter duration of antimicrobial therapy may have benefits in patients with CAP, as it might enhance compliance, decrease the development of antimicrobial resistance, decrease the incidence and shorten the duration of adverse drug effects, reduce treatment costs and improve patient satisfaction with therapy. Nevertheless, remaining questions regarding the influence of patient selection, disease severity or choice of antimicrobial for short-course therapy indicate the need for further randomized controlled clinical trials in this area of research. This article summarizes current evidence for short-course therapy in patients with CAP and draws conclusions for clinical practice.

Streptococcus pneumoniae in nasopharyngeal secretions of healthy children: comparison of real-time PCR and culture from STGG-transport medium

Precise methods for the detection of Streptococcus pneumoniae are needed for predicting the consequences of pneumococcal conjugate vaccines on nasopharyngeal carriage. In this study, 400 nasopharyngeal swab samples from children were analyzed using a real-time pneumolysin (ply)-PCR method. The specimens were originally collected into STGG-transport medium and cultured in 1999, after which they were stored at -80 degrees C until analyzed by real-time PCR in 2001. The sensitivities of real-time PCR and culture methods were also studied by analyzing 10-fold dilutions of a pneumococcal broth culture using both methods. Of the 400 nasopharyngeal swab samples, 158 (40%) were positive in culture and 276 (69%) by real-time PCR. A minor part (4%) of the culture-positive samples remained negative by PCR. There was a trend between the quantity of genome equivalents detected by PCR and the number of colonies found in culture. When analyzing 10-fold dilutions of a pneumococcal broth culture, a higher number of genome equivalents were detected using real-time PCR than the number of colonies detected by culture. Quantitative real-time PCR provides feasible means for quantifying pneumococcal carriage. Further studies are needed to confirm that positive PCR findings really indicate the presence of viable pneumococcus in nasopharyngeal specimens.

Serotype-specific pneumococcal antibodies in breast milk of Gambian women immunized with a pneumococcal polysaccharide vaccine during pregnancy

BACKGROUND

In breast-feeding populations, immunization during pregnancy with pneumococcal polysaccharide offers a potentially useful approach to preventing pneumococcal disease in young infants.

METHODS

Breast milk samples were collected at 0, 2, 4 and 6 months after delivery from Gambian women vaccinated during pregnancy (24-32 weeks gestation) with Pneumovax II (n = 56) or Mengivax A&C (n = 57). Specimens were examined for secretory immunoglobulin A (s-IgA) concentration, subclass distribution and avidity specific to pneumococcal serotypes 4, 6B, 14, 19F and 23F and the antigen mixture in Pneumovax II by enzyme-linked immunosorbent assay. Colostral s-IgA and IgG concentrations in paired maternal sera were compared.

RESULTS

Colostral s-IgA concentrations specific to all pneumococcal polysaccharide antigens investigated were significantly higher (P < 0.05) among Pneumovax II vaccinees. Titers specific to serotypes 4, 6B and 14 and the vaccine formula remained significantly higher during 6 months, and those for 19F were higher during 4 months. Significantly higher concentrations of vaccine antigen-specific s-IgA antibody were sustained for 6 months after delivery (P = 0.011). Comparison of colostral s-IgA and IgG in serum revealed a significant correlation only among Mengivax A&C vaccinees for pneumococcal polysaccharide 23F (rs= 0.68; P < or = 0.0001). Vaccination elicited trends toward increased s-IgA2, reaching significance for serotype 14 and the vaccine formula. Immunization elicited significantly higher s-IgA avidities specific to all pneumococcal polysaccharide antigens studied during 6 months.

CONCLUSIONS

The public health value of immunization during pregnancy with pneumococcal polysaccharide vaccine in breast-feeding populations warrants further evaluation, particularly in populations with a high incidence of pneumococcal disease in early infancy.

Mucosal immunology of vaccines against pathogenic nasopharyngeal bacteria

The introduction of Haemophilus influenzae type b conjugate vaccines during the 1990s was followed by dramatic decreases both in the incidence of Haemophilus influenzae type b related invasive disease and in nasopharyngeal carriage of the organism. The extent of this effect has been influenced by the fact that Haemophilus influenzae type b conjugate vaccines reduce nasopharyngeal carriage and induce herd immunity. Based on the success of Haemophilus influenzae type b conjugate vaccines, chemical conjugation has been applied to the development of pneumococcal and meningococcal polysaccharide conjugate vaccines. Evidence has begun to accumulate that these new polysaccharide based conjugate vaccines can also reduce nasopharyngeal carriage and can induce immune responses at the local mucosal level, which may be responsible for these effects. This article reviews recent studies on mucosal immune responses induced by polysaccharide based vaccines and some protein vaccine antigens against several pathogenic nasopharyngeal bacteria, and discusses the mechanisms and functions of these immune responses that may help our understanding of mucosal immune responses to both immunisation and infection.

Community-wide vaccination with the heptavalent pneumococcal conjugate significantly alters the microbiology of acute otitis media

BACKGROUND

Community-wide use of conjugated heptavalent pneumococcal vaccine (PCV7) in children <2 years of age could affect the microbiology of acute otitis media (AOM) in vaccinees, particularly for penicillin-nonsusceptible Streptococcus pneumoniae (PNSP).

SETTING

Since Summer 2000, 94% of young children cared for by this 7-clinician, pediatric practice in rural central Kentucky received 3 or 4 doses of PCV7 in the first 18 months of life.

OBJECTIVE

To determine changes in microbiology of AOM before and after community-wide routine implementation of PCV7.

METHODS

Among children 7-24 months old with severe or refractory AOM, we compared 336 AOM isolates from 1992-1998 with 83 AOM isolates from 2000-2003 in children who had received 3 or 4 doses of PCV7.

RESULTS

Comparing each cohort (1992-1998 versus 2000-2003), the proportion of S. pneumoniae decreased from 48% to 31% (P = 0.009; relative risk, 0.754; 95% confidence interval, 0.628-0.906), and nontypable Haemophilus influenzae increased from 41% to 56% (P = 0.01; relative risk, 1.87; 95% confidence interval, 1.15-3.04; beta-lactamase-positive, 56% versus 64%, not significant). The proportions of intermediate PNSP and resistant PNSP, respectively, were 16% and 9% versus 13% and 6% pre- and post-PCV7, respectively. Vaccine and vaccine-related serotypes, respectively, comprised 70% and 8% versus 36% and 32% of S. pneumoniae strains (P = 0.003). Post-PCV7, Gram-negative bacteria and beta-lactamase-producing organisms accounted for two-thirds and one-half of all AOM isolates, respectively.

DISCUSSION

The overall proportion of S. pneumoniae isolates and vaccine serotypes in AOM were significantly reduced by community-wide use of PCV7 vaccine in our practice. The proportion of Gram-negative bacteria became 2-fold more frequent than S. pneumoniae in AOM in PCV7-vaccinated young children where PCV7 uptake was community-wide and supply was adequate.

What can children gain from pneumococcal conjugate vaccines?

In excess of 1 million young children die every year as a consequence of disease caused by Streptococcus pneumoniae, the vast majority in developing countries. Although the first vaccine against the Pneumococcus was produced before the First World War, licensure of the first vaccine with documented efficacy against severe infections in infants and young children did not occur until February 2000 in the United States. This conjugate vaccine consists of purified polysaccharide, from each of seven pneumococcal serotypes, chemically linked to a carrier protein. A high degree of efficacy of the new vaccine against potentially life-threatening infections has been shown in both poor and affluent countries. The vaccine's potential to protect from acute otitis media, however, is very limited, although encouraging indirect effects, such as reduced antibiotic prescriptions, have been reported. An inherent problem with the new pneumococcal conjugate vaccines is that, while more than 20 pneumococcal serotypes may cause invasive disease, only a more limited number of polysaccharides, 11 or so, can in practice be conjugated to carrier protein as part of a single vaccine formulation. Because of variation in the ranking of serotypes most commonly responsible for pneumococcal disease, by region, age and disease manifestation, compromise was required in selecting serotype-specific saccharides for inclusion.

CONCLUSION

Complex conjugate technology comes at a price, and the present costs keep most of the world's children far out of reach of an effective vaccine. However, the pneumococcal conjugate vaccine is a highly functional weapon against deadly pneumococcal infections, and strenuous efforts are needed to maximise its accessibility to children most at risk.

Short- and long-term effects of pneumococcal conjugate vaccination of children on penicillin resistance

Recent observations have shown that wide-scale vaccination with pneumococcal conjugate vaccines was associated with a reduction in invasive disease, supporting the expectation that vaccination could help reduce carriage of Streptococcus pneumoniae and control the spread of resistant strains. However, it is too early to assess whether these effects can be sustained in the long term. Here, we used mathematical modeling to investigate time changes in pneumococcal colonization and resistance induced by conjugate vaccination in an environment where antibiotic exposure is high and resistance is widespread. According to model predictions, vaccination induced a decrease in carriage of vaccine-type pneumococci to very low levels, typically in 10 to 15 years under epidemiologically realistic conditions. Almost simultaneously, non-vaccine-type pneumococci spread in the community. Consequently, while there was a short-term decrease in the overall carriage rate, it was followed after a few years by a renewed, although limited, increase. Vaccination with a heptavalent vaccine did not affect the extent to which antibiotic resistance was selected: in all cases, the distribution of resistance levels peaked at high levels (MIC > 2 microg/ml) after 20 years. With a vaccine optimally designed to include all serotypes currently exhibiting decreased susceptibility to penicillin G, the selection of resistance was slowed down, although not prevented. These results suggest that because of serotype replacement, the effects of vaccination observed today may not be sustained in the long term. As a consequence, vaccination alone may not be successful in controlling selection for resistance in S. pneumoniae.

Antibiotic susceptibility in relation to penicillin-binding protein genes and serotype distribution of Streptococcus pneumoniae strains responsible for meningitis in Japan, 1999 to 2002

The antibiotic susceptibilities, genotypes of penicillin (PEN)-binding protein genes (pbp), and serotype distributions of Streptococcus pneumoniae isolates from meningitis patients were investigated by a nationwide surveillance group in Japan between 1999 and 2002. We analyzed 146 isolates from children (</=17 years old) and 73 from adults (>/=18 years old). Isolates with or without abnormal pbp1a, pbp2x, or pbp2b genes identified by PCR were classified into six genotype patterns and 90% MIC (MIC(90)) values for PEN: (i) strains with three normal genes (17.2% of isolates; MIC(90), 0.031 micro g/ml); (ii) strains with abnormal pbp2x (22.1%, 0.063 micro g/ml); (iii) strains with abnormal pbp2b (1.0%, 0.125 micro g/ml); (iv) strains with abnormal pbp2x and pbp2b (7.4%, 0.25 micro g/ml); (v) strains with abnormal pbp1a and pbp2x (12.7%, 0.25 micro g/ml); and (vi) strains with three abnormal PBP genes (39.7%, 4 micro g/ml), which are termed genotypic PEN-resistant S. pneumoniae (gPRSP). Panipenem, a carbapenem, showed an excellent MIC(90) (0.125 micro g/ml) against gPRSP, followed by meropenem and vancomycin (0.5 micro g/ml), cefotaxime and ceftriaxone (1 micro g/ml), and ampicillin (4 micro g/ml). Strains of gPRSP were significantly more prevalent in children (45.2%) than in adults (27.4%). The most frequent serotypes were 6B, 19F, 23F, 6A, and 14 in children and 23F, 22, 3, 10, 6B, and 19F in adults. Serotypes 6B, 6A, 19F, 23F, and 14 predominated among gPRSP. In children, 7- and 11-valent pneumococcal conjugate vaccines would cover 76.2 and 81.3% of isolates, respectively, although coverage would be lower in adults (43.9 and 56.0%, respectively). These findings suggest the need for early introduction of pneumococcal conjugate vaccines and continuous bacteriological surveillance for meningitis.

Mucosal immune responses to capsular pneumococcal polysaccharides in immunized preschool children and controls with similar nasal pneumococcal colonization rates

BACKGROUND

Immunization with conjugate pneumococcal vaccines induces significant primary and memory IgG anti-polysaccharide (PS) responses in serum. It can also induce mucosal responses in infants especially after a polysaccharide booster. However, it is unclear whether it can prime for mucosal memory responses on nasal exposure to pneumococcus, which may be important in protection against pneumococcal invasion and/or carriage.

METHOD

IgA and IgG to serotypes 4, 6B, 9V, 14, 18C, 19F and 23F (conjugate vaccine serotypes), 1 and 3 (nonvaccine serotypes) capsular PS were measured by immunoassay in saliva from 2- to 5-year-old children previously given three doses of 7-valent pneumococcal conjugate vaccine in infancy, followed by 23-valent PS vaccine at 13 months and from unvaccinated controls of similar age and sex. Salivary antibody responses were analyzed in relation to carriage of pneumococci assessed by bacterial culture of nasopharyngeal swab samples collected in the summer and winter of the year 2000.

RESULTS

Rates of detectable IgG antibodies to all vaccine serotypes except 23F were higher in subjects than in controls. No such differences were observed for IgA antibodies except for serotype 6B. Nasal colonization rates were similar, and in both groups mucosal IgA responses were more common and larger than IgG responses.

CONCLUSIONS

The mucosal anti-capsular IgA responses observed could develop in response to colonization in preschool children, regardless of vaccination status, and contribute to the falling carriage rates observed with increasing age.

The cost-effectiveness of pneumococcal conjugate vaccination in Australia

BACKGROUND

Pneumococcal conjugate vaccine, 7 valent (PCV7) is the most costly vaccine yet considered for publicly funded programs. In mid 2001, Australia funded PCV7 for high-risk groups only (indigenous children and children with certain underlying medical conditions). World wide, non-industry-funded studies and studies using cost-utility measures are sparse. We undertook an independent economic analysis of PCV7 compared with no vaccination in the non high-risk Australian childhood population using cost-utility and cost-effectiveness measures.

METHODS

The incidence of invasive pneumococcal disease (IPD), non-bacteraemic pneumonia and otitis media was estimated using representative urban Australian data, or by extrapolation from comparable industrialised countries. A decision-analytic model was developed for a hypothetical birth cohort using the age-specific vaccine coverage from the Californian randomised controlled trial of PCV7. Health outcomes were measured by life-years saved and deaths and disability-adjusted life-years (DALYs) averted. In line with government guidelines, only direct costs were considered in 1997-1998 Australian dollars.

RESULTS

For a birth cohort of 250,000, the gross cost of vaccination is $ 78.6 million. Subtracting treatment cost savings, the net cost (discounted) is $ 61.7 million. In undiscounted terms, vaccination prevents 13.7 deaths, 11.2 (82%) from IPD and the remainder from non-bacteraemic pneumonia. The discounted cost per death avoided is $ 5.0 million, per life-year saved $ 230,130 and per DALY averted $ 121,100, giving a break-even vaccine price of $ 15.40 per dose. These estimates are most sensitive to the unit cost per dose of vaccine, estimates of incidence and vaccine efficacy against non-bacteraemic pneumonia and the discount rate. The cost per DALY reduced to $ 81,000 with a discount rate of 3% rather than 5% and to $ 90,000 with the most favourable assumptions concerning pneumonia reduction.

DISCUSSION

With a vaccine price of $ 90 per dose, mid-range estimates of impact against non-bacteraemic pneumonia, and discount rate of 5%, a PCV7 program for infants not at high risk of IPD is at the upper limit of cost per DALY previously approved under Australian pharmaceutical funding guidelines. The impact of PCV7 against non-bacteraemic pneumonia is poorly defined, but its importance to cost-effectiveness in resource rich and resource poor settings warrants further studies or analysis to give greater precision to this outcome.

Streptococcus pneumoniae colonisation: the key to pneumococcal disease

Streptococcus pneumoniae is an important pathogen causing invasive diseases such as sepsis, meningitis, and pneumonia. The burden of disease is highest in the youngest and oldest sections of the population in both more and less developed countries. The treatment of pneumococcal infections is complicated by the worldwide emergence in pneumococci of resistance to penicillin and other antibiotics. Pneumococcal disease is preceded by asymptomatic colonisation, which is especially high in children. The current seven-valent conjugate vaccine is highly effective against invasive disease caused by the vaccine-type strains. However, vaccine coverage is limited, and replacement by non-vaccine serotypes resulting in disease is a serious threat for the near future. Therefore, the search for new vaccine candidates that elicit protection against a broader range of pneumococcal strains is important. Several surface-associated protein vaccines are currently under investigation. Another important issue is whether the aim should be to prevent pneumococcal disease by eradication of nasopharyngeal colonisation, or to prevent bacterial invasion leaving colonisation relatively unaffected and hence preventing the occurrence of replacement colonisation and disease. To illustrate the importance of pneumococcal colonisation in relation to pneumococcal disease and prevention of disease, we discuss the mechanism and epidemiology of colonisation, the complexity of relations within and between species, and the consequences of the different preventive strategies for pneumococcal colonisation.

Bacterial polysaccharide-protein conjugate vaccines

Following demonstration that chemical conjugation of polysaccharide antigens to proteins could enhance their immunogenicity in the 1920s, interest in this approach to primary prevention of bacterial infections waned with the development and widespread use of antibiotics. Emergence of resistant bacteria rekindled interest in the late 20th century, which saw extremely rapid development and implementation of several vaccines which are already rapidly changing the epidemiology of childhood infections with Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. Others such as Group B streptococcus and Salmonella typhi infections may soon follow. However, several important questions about the immunology of these antigens remain unanswered and the long-term implications of reducing or eliminating the circulation of organisms which are more commonly nasopharyngeal commensals than pathogenic invaders are uncertain.

Changes in treatment strategies for acute otitis media after full implementation of the pneumococcal seven valent conjugate vaccine

BACKGROUND

Administration of the pneumococcal seven valent conjugate vaccine (PCV-7) results in significant reductions in the incidence of invasive pneumococcal disease and nasopharyngeal colonization rates; however, the reduction in the overall incidence of acute otitis media (AOM) is minimal. Despite an ongoing shortage of PCV-7 in the United States, during which children are receiving fewer doses at longer intervals than the recommended dosing schedule, the incidence of invasive pneumococcal disease in young children has continued to decrease.

PURPOSE

The purpose of this article is to review why the reported effect of PCV-7 on AOM infection rates does not match the reduction in invasive pneumococcal disease or the reduction in nasopharyngeal carriage of Streptococcus pneumoniae.

METHODS

The potential effect of a fully implemented PCV-7 schedule on AOM infections is calculated based on serotype-specific AOM reduction rates observed in clinical studies. Clinical success rates of various antimicrobials used in the treatment of AOM in children fully immunized with PCV-7 also are calculated based on projected PCV-7-induced changes in pathogen profiles and documented antimicrobial resistance rates. Questions regarding potential serotype substitution in children with AOM but not invasive pneumococcal disease, the increased incidence of infection with Haemophilus influenzae in children immunized with PCV-7 and the possibility of herd immunity also will be addressed.

RESULTS

Although the majority of penicillin-nonsusceptible S. pneumoniae are included in PCV-7, AOM caused by these strains will not completely disappear, especially in children 24 months of age and younger.

CONCLUSIONS

Consequently, clinicians must continue to consider penicillin-nonsusceptible pneumococci when prescribing antimicrobials for AOM.

Vaccination of day-care center attendees reduces carriage of Streptococcus pneumoniae among their younger siblings

AIM

We conducted a study to determine whether administration of a pneumococcal conjugate vaccine to toddlers attending day-care centers (DCCs) could prevent acquisition of Streptococcus pneumoniae of the vaccine serotypes (VT) by their younger siblings.

METHODS

In a double blind study, 262 DCC attendees ages 12 to 35 months were randomized to receive a 9-valent pneumococcal conjugate vaccine (PnCRM9; n = 132), or a control vaccine (meningococcus C vaccine; n = 130). It was planned to follow the groups for 2 years with monthly nasopharyngeal pneumococcal cultures during the first follow-up year and every 2 months during the second year. Forty-six younger siblings of the above described children, age <18 months (23 siblings of the PnCRM9 recipients and 23 of the controls), were also enrolled, and nasopharyngeal cultures were obtained monthly until the children reached the age of 18 months or started to attend DCC, if before the age of 18 months. Pneumococcal isolates were serotyped and tested for antibiotic susceptibility.

RESULTS

Of the 3748 cultures obtained from the DCC attendees, 2450 (65%) were positive for S. pneumoniae. Of 306 cultures obtained from the younger siblings, 151 (49%) were positive. Among the PnCRM9 recipients, cultures were significantly less frequently positive for the VT S. pneumoniae than among the controls (13% vs. 21%, respectively; P < 0.001). The same pattern was seen in the younger siblings of PnCRM9 recipients vs. the siblings of controls (21% vs. 34%, respectively; P = 0.017). The reverse trend was seen for non-VT strains in both the DCC attendees (44% vs. 34%, respectively; P < 0.001) and their younger siblings (19% vs. 13%, respectively; P = 0.15). There was a significant decrease in the carriage rate of antibiotic-resistant S. pneumoniae in both the PnCRM9 recipients and their younger siblings. The relative risks (and 95% confidence intervals) to carry S. pneumoniae penicillin-nonsusceptible, resistant to > or =1, > or =2 and > or =3 antibiotic categories among younger siblings of PnCRM9 recipients vs. siblings of controls were 0.47 (0.31 to 0.70), 0.49 (0.33 to 0.71), 0.46 (0.30 to 0.73) and 0.49 (0.21 to 1.17), respectively. When acquired, VT and antibiotic-resistant S. pneumoniae were carried for a significantly shorter period of time among siblings of PnCRM9 recipients than in siblings of controls.

CONCLUSION

The marked effect of PnCRM9 administration to DCC attendees on carriage of VT and antibiotic-resistant S. pneumoniae among their younger household close contacts demonstrates a herd effect of the vaccine.

Effect of a nonavalent conjugate vaccine on carriage of antibiotic-resistant Streptococcus pneumoniae in day-care centers

BACKGROUND

In the developed societies, day-care centers (DCCs) play an important role in the spread of antibiotic-resistant pneumococci both within the facility and from the facility to the community. This study was conducted to determine the effect of a nonavalent pneumococcal conjugate vaccine (PCV-9) on the carriage of antibiotic-resistant pneumococci in the DCC.

SUBJECTS AND METHODS

Healthy DCC attendees ages 12 to 35 months were randomized to receive either PCV-9 or a control vaccine (conjugate meningococcus C vaccine) in a double blinded manner. Nasopharyngeal Streptococcus pneumoniae cultures were obtained from each subject before vaccination, monthly during the first year of follow-up and every 2 to 3 months during the second year of follow-up. For each isolate the serotype and antibiotic susceptibility were determined.

RESULTS

A total of 132 and 130 evaluable toddlers received either PCV-9 or the control vaccine, respectively. In total 3748 cultures were obtained, of which 2450 (65%) were positive for S. pneumoniae. The resistance rates to penicillin, trimethoprim-sulfamethoxazole and erythromycin were 36, 35 and 16%, respectively. Resistance rates to > or =1 and > or =3 antibiotic categories were 52 and 9%, respectively. Antibiotic resistance was found mainly in the 5 serotypes included in the pneumococcal conjugate vaccines (6B, 9V, 14, 19F and 23F) and in 2 related serotypes (6A and 19A). In the vaccinated group a clear and significant reduction of the carriage rate of the serotypes included in the vaccine and the related serotype 6A as well as an increase in the carriage rate of the serotypes not included in the vaccine were observed. In parallel a significant decrease in carriage rate of antibiotic-resistant pneumococci was observed. The reduction of carriage of antibiotic-resistant pneumococci was seen in all age windows but was greater in the age window <36 months.

CONCLUSIONS

The carriage rate of antibiotic-resistant S. pneumoniae, including multiply resistant S. pneumoniae, in DCC attendees is high. Pneumococcal conjugate vaccines seem to be an important tool for reducing the carriage rate of antibiotic-resistant pneumonia in DCCs.

Serotypes of respiratory tract isolates of Streptococcus pneumoniae from Jamaican children

BACKGROUND

Data are lacking on the pneumococcal serotypes present in many developing regions, including the Caribbean. We examined the serotypes of nasopharyngeal (NP) isolates of pneumococci obtained from Jamaican children.

METHODS

We obtained NP samples from children seen in the Emergency Department at the Bustamante Children's Hospital. The samples were transported to Canada for isolation and serotyping of pneumococci.

RESULTS

We obtained 94 isolates from 276 children; median age 3.4 years. The majority (57%) had symptoms of acute respiratory infection at the time of sampling. The main serotypes carried were 6B (20.5%), 19F (14.5%), and 14 (8.4%). Non-typable isolates accounted for 10.8% of the isolates. Fifty-nine per cent of the serotypes were present among the 11 being considered for candidate pneumococcal conjugate vaccines (95% CI 48-70%); the corresponding proportion present in the recently licensed 7-valent vaccine was 57% (95% CI 45-67%). A significant proportion of the serotypes found is absent from those to be included in future conjugate vaccines (P<0.0001; reference=85% expected serotype representation). Less than 5% of isolates were non-susceptible to penicillin (3.2%), cefotaxime-ceftriaxone (3.2%) and cefuroxime (3.2%), while 8.4% and 1.l% of isolates were resistant to trimethoprim-sulfamethoxazole and erythromycin respectively. There were three isolates with resistance to two or more classes of drug. These isolates were all resistant to penicillin (MIC 2 micro g/mL); the serotypes were 14, 23F, and 19F.

CONCLUSION

A significant proportion of the serotypes found is absent from those to be included in future conjugate vaccines.

Pneumococcal nasopharyngeal carriage in children following heptavalent pneumococcal conjugate vaccination in infancy

AIMS

To ascertain whether the reduction in nasopharyngeal carriage of vaccine serotypes induced by pneumococcal conjugate vaccine (PnCV) administered to infants persists beyond the age of 2 years.

METHODS

Non-randomised, unblinded controlled study of 2-5 year old children who had received three doses of heptavalent PnCV (7VPnCV) in infancy and 23-valent pneumococcal polysaccharide vaccine at 13 months, and unimmunised controls. Nasopharyngeal swabs were taken in summer (150 vaccinated subjects, 126 controls) and winter (143 vaccinated subjects, 188 controls). The swabs were cultured and serotyped for Streptococcus pneumoniae.

RESULTS

Carriage rates (vaccinated subjects: 24.7% and 43.4%; controls: 27.0% and 41.0%, in summer and winter respectively) and carriage of vaccine serotypes (subjects: 10.0% and 30.0%; controls: 13.5% and 31.5%, in summer and winter respectively) were similar in the two groups.

CONCLUSIONS

Effects of vaccination in infancy on rates of nasal carriage of pneumococcus and serotype replacement in children living in a largely unvaccinated population are no longer evident by 2-5 years of age.

Impact of the pneumococcal conjugate vaccine on otitis media

CONTEXT

The heptavalent pneumococcal conjugate vaccine (PCV) is recommended for infants to protect against invasive disease, but its impact on otitis might also have public health importance.

OBJECTIVE

To examine the impact of PCV on the incidence of otitis media, frequent otitis media and tympanostomy tube procedures and to assess whether the effectiveness of the vaccine wanes after age 24 months and varies by race, sex or season.

DESIGN, SETTING AND PATIENTS

From 1995 to 1998, 37 868 children at Kaiser Permanente in Northern California were randomized to receive PCV or a control vaccine in a double blind trial and were followed through April 1999.

INTERVENTIONS

Children received a primary series at 2, 4 and 6 months of age and a booster at 12 to 15 months.

MAIN OUTCOME MEASURES

Visits for otitis, frequent visits for otitis and tympanostomy tube procedures. Otitis was ascertained from diagnosis checklists routinely marked by physicians.

RESULTS

Control children averaged 1.8 otitis visits per year. Children given PCV had fewer otitis visits than control children in every age group, sex, race and season examined. Intention-to-treat analysis permitted rejection of the null hypothesis that PCV is ineffective against otitis media (P < 0.0001). In children who completed the primary series per protocol, PCV reduced otitis visits by 7.8% [95% confidence interval (CI), 5.4 to 10.2%] and antibiotic prescriptions by 5.7% (CI 4.2 to 7.2%). Frequent otitis was reduced by amounts that increased with otitis frequency, from a 10% reduction in the risk of 3 visits to a 26% reduction in the risk of 10 visits within a 6-month period. Tube placements were reduced by 24% (CI 12 to 35%).

CONCLUSION

In children followed up to 3.5 years, PCV provided a moderate amount of protection against ear infections while reducing frequent otitis media and tube procedures by greater amounts.

Interactions among strategies associated with bacterial infection: pathogenicity, epidemicity, and antibiotic resistance

Infections have been the major cause of disease throughout the history of human populations. With the introduction of antibiotics, it was thought that this problem should disappear. However, bacteria have been able to evolve to become antibiotic resistant. Nowadays, a proficient pathogen must be virulent, epidemic, and resistant to antibiotics. Analysis of the interplay among these features of bacterial populations is needed to predict the future of infectious diseases. In this regard, we have reviewed the genetic linkage of antibiotic resistance and bacterial virulence in the same genetic determinants as well as the cross talk between antibiotic resistance and virulence regulatory circuits with the aim of understanding the effect of acquisition of resistance on bacterial virulence. We also discuss the possibility that antibiotic resistance and bacterial virulence might prevail as linked phenotypes in the future. The novel situation brought about by the worldwide use of antibiotics is undoubtedly changing bacterial populations. These changes might alter the properties of not only bacterial pathogens, but also the normal host microbiota. The evolutionary consequences of the release of antibiotics into the environment are largely unknown, but most probably restoration of the microbiota from the preantibiotic era is beyond our current abilities.

Current state of pneumococcal vaccines

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, and acute otitis media in children and adults worldwide. According to World Health Organization estimates, at least 1 million children under 5 years of age die each year from pneumococcal pneumonia. The emergence of resistant strains necessitates the development of an effective vaccine with a large serotype coverage. The 11 most common serotypes cause 72-83% of all serious pneumococcal diseases worldwide. Currently marketed 23-valent pneumococcal polysaccharide vaccine provides large serotype coverage and offers a less expensive option. However, it is efficacious only in adults but not in infants. Conjugate vaccines offer a solution by generating immunological memory already at early age. A recently licensed 7-valent conjugate vaccine is immunogenic and efficacious in infants. Its serotype coverage might be sufficient in Europe and North America, but not in Africa, Asia and Oceania. A need exists to develop pneumococcal vaccines with lower cost and larger serotype coverage. Several 11-valent pneumococcal conjugate vaccines are being evaluated in phase I-III trials. This study reviews the current state of pneumococcal problem and pneumococcal vaccines in clinical use.

Should the new pneumococcal vaccine be used in high-risk children?

A new conjugate 7-valent vaccine to prevent pneumococcal infection (Prevenar, Wyeth) has recently received a European licence for use in young healthy children. The vaccine is not currently included in the universal immunisation schedule in the UK or elsewhere in Europe, although it is being used widely in the USA. Its availability for purchase raises the question whether paediatricians should consider using it in high risk children, including those for whom the polysaccharide 23-valent vaccine was previously recommended, until (or unless) it is introduced into general use-indeed the Chief Medical Officer for England and Wales has recently made a recommendation regarding such children aged less than 2 years. We review the evidence concerning use of the vaccine in such children and make suggestions as to how the vaccine may be used while further information is collected.

Capsulate bacteria and the lung

Capsulate bacteria cause the majority of community-acquired pneumonia presenting to hospital world-wide, at all ages. They are united by the virulence factor of their differing capsular polysaccharides, enabling them to evade phagocytosis. All cause invasive disease beyond the respiratory tract, including septicaemia and central nervous system infection. Recent advances in vaccine development have made the capsular polysaccharide an achievable target for vaccine strategies across all ages, with impacts already seen upon Streptococcus pneumoniae and Haemophilus influenzae type b pneumonia in countries able to afford these new vaccines.