The epidemiology of Haemophilus influenzae type b disease in the Republic of Ireland

Association of secondhand smoke exposure with pediatric invasive bacterial disease and bacterial carriage: a systematic review and meta-analysis

BACKGROUND

A number of epidemiologic studies have observed an association between secondhand smoke (SHS) exposure and pediatric invasive bacterial disease (IBD) but the evidence has not been systematically reviewed. We carried out a systematic review and meta-analysis of SHS exposure and two outcomes, IBD and pharyngeal carriage of bacteria, for Neisseria meningitidis (N. meningitidis), Haemophilus influenzae type B (Hib), and Streptococcus pneumoniae (S. pneumoniae).

METHODS AND FINDINGS

Two independent reviewers searched Medline, EMBASE, and selected other databases, and screened articles for inclusion and exclusion criteria. We identified 30 case-control studies on SHS and IBD, and 12 cross-sectional studies on SHS and bacterial carriage. Weighted summary odd ratios (ORs) were calculated for each outcome and for studies with specific design and quality characteristics. Tests for heterogeneity and publication bias were performed. Compared with those unexposed to SHS, summary OR for SHS exposure was 2.02 (95% confidence interval [CI] 1.52-2.69) for invasive meningococcal disease, 1.21 (95% CI 0.69-2.14) for invasive pneumococcal disease, and 1.22 (95% CI 0.93-1.62) for invasive Hib disease. For pharyngeal carriage, summary OR was 1.68 (95% CI, 1.19-2.36) for N. meningitidis, 1.66 (95% CI 1.33-2.07) for S. pneumoniae, and 0.96 (95% CI 0.48-1.95) for Hib. The association between SHS exposure and invasive meningococcal and Hib diseases was consistent regardless of outcome definitions, age groups, study designs, and publication year. The effect estimates were larger in studies among children younger than 6 years of age for all three IBDs, and in studies with the more rigorous laboratory-confirmed diagnosis for invasive meningococcal disease (summary OR 3.24; 95% CI 1.72-6.13).

CONCLUSIONS

When considered together with evidence from direct smoking and biological mechanisms, our systematic review and meta-analysis indicates that SHS exposure may be associated with invasive meningococcal disease. The epidemiologic evidence is currently insufficient to show an association between SHS and invasive Hib disease or pneumococcal disease. Because the burden of IBD is highest in developing countries where SHS is increasing, there is a need for high-quality studies to confirm these results, and for interventions to reduce exposure of children to SHS.

Long-term complications and risk of other serious infections following invasive Haemophilus influenzae serotype b disease in vaccinated children

This study describes the long-term complications in children with Haemophilus influenzae serotype b (Hib) vaccine failure and to determine their risk of other serious infections. The families of 323 children with invasive Hib disease after appropriate vaccination (i.e. vaccine failure) were contacted to complete a questionnaire relating to their health and 260 (80.5%) completed the questionnaire. Of the 124 children with meningitis, 18.5% reported serious long-term sequelae and a further 12.1% of parents attributed other problems to Hib meningitis. Overall, 14% (32/231 cases) of otherwise healthy children and 59% (17/29 cases) of children with an underlying condition developed at least one other serious infection requiring hospital admission. In a Poisson regression model, the risk of another serious infection was independently associated with the presence of an underlying medical condition (incidence risk ratio (IRR) 7.6, 95% CI 4.8-12.1; p<0.0001), both parents having had a serious infection (IRR 4.1, 95% CI 1.6-10.3; p=0.003), requirement of more than two antibiotic courses per year (IRR 2.3, 95% CI 1.4-3.6; p=0.001) and the presence of a long-term complication after Hib infection (IRR 1.8, 95% CI 1.1-3.1; p=0.03). Thus, rates of long-term sequelae in children with vaccine failure who developed Hib meningitis are similar to those in unvaccinated children in the pre-vaccine era. One in seven otherwise healthy children (14%) with Hib vaccine failure will go on to suffer another serious infection requiring hospital admission in childhood, which is higher than would be expected for the UK paediatric population.

Haemophilus influenzae serotype b conjugate vaccine failure in twelve countries with established national childhood immunization programmes

The present study describes the clinical and immunological features of children with Hib vaccine failure, who were identified through national surveillance between 1996 and 2001 in Europe, Israel and Australia. True vaccine failure was defined as invasive Hib disease occurring ≥2 weeks after one dose, given after the first birthday, or ≥1 week after ≥2 doses, given at <1 year of age. Of the 423 cases (representing 0.2 cases per 100,000 child-years at risk) reported, 330 (78%) had received three doses in the first year of life and developed disease at a median age of 28 months. Of the remaining 93, 48 had received two doses in infancy, 34 had received four doses including a booster, and 11 had received a single dose after 12 months of age. These children developed disease at a median age of 12, 33 and 71 months, respectively. In total, 47 out of 258 children (18%) with available information had an underlying medical problem (including prematurity) and 53 out of 161 (33%) had immunoglobulin deficiency. Convalescent Hib antibody concentrations were above the putative protective concentration of 1.0 mg/L in 147/194 (76%) children; low concentrations were associated with both the presence of an underlying medical problem and young age at the time of Hib disease. Almost all children who received an additional vaccine dose developed antibodies at protective concentrations. Thus, Hib vaccine failure is rare, but can occur with any immunization schedule. Children with Hib vaccine failure should have immunoglobulin and convalescent Hib antibody concentrations measured after infection and receive additional vaccination, if required.

Changes in ascertainment of Hib and its influence on the estimation of disease incidence in the United Kingdom

Enhanced surveillance for Hib infection, initially covering Wales and five English regions, began in 1990 and in 1995 was extended to the whole of England and Wales. To determine whether changes in the ascertainment of Haemophilus influenzae may have affected estimates of Hib disease incidence, data from January 1990 to December 2003 were analysed. A total of 8887 and 4020 (45%) cases of H. influenzae and Hib respectively were reported. The proportion of isolates that were serotyped increased over time, and therefore reported incidence may have underestimated the true incidence in the early years of the study. Adjusting for this under-ascertainment, the incidence in children aged <5 years declined from a peak of 28.3/100,000 in 1991 to 0.97/100,000 in 1998 and increased to 3.8/100,000 in 2003. Following the implementation of universal vaccination a dramatic decline in the true incidence of invasive Hib disease occurred. The observation of the subsequent resurgence was real but the highest incidence reached was 85% below the corrected incidence in the pre-vaccine era. Continued high-quality surveillance is needed in order to accurately monitor and detect changes in disease incidence.

Invasive Haemophilus influenzae disease: an ecological study of sociodemographic risk factors before and after the introduction of Hib conjugate vaccine

This study examines the impact of H. influenzae type b (Hib) conjugate vaccine on sociodemographic risk factors for invasive H. influenzae disease in the 2 years before and immediately after the introduction of Hib conjugate vaccine. An ecological study design was used and cases were identified using active surveillance employing several surveillance systems. The study population comprised all children aged < 5 years resident in the West Midlands, an English health region, with laboratory confirmed invasive disease 2 years before (1990-1992) and 2 years after (1992-1994) the introduction of Hib conjugate vaccine. Selected sociodemographic variables derived from the UK census were obtained for all census enumeration districts in the region. Each variable was then ranked and divided into six categories. Linear associations between disease rates and sociodemographic variables were examined. Overall, there was a significant reduction in the incidence of invasive H. influenzae disease. In the pre-conjugate vaccine era there were trends of decreasing disease incidence with increasing child population density (p = 0.012) and total population density (p = 0.0023). In the post-conjugate vaccine period, total population density (p = 0.0275) remained significant and a trend of increasing disease incidence with increasing population mobility (p = 0.0012) was seen. Although Hib conjugate vaccine has resulted in a dramatic reduction in disease incidence changes in sociodemographic risk factors were identified in the post-conjugate vaccine period, particularly population mobility. Our results may have implications for current and future vaccine strategies.

Clinical and immunological risk factors associated with Haemophilus influenzae type b conjugate vaccine failure in childhood

Haemophilus influenzae type b (Hib) conjugate vaccines have proved extremely efficacious in healthy children. True Hib vaccine failures are rare. Hib conjugate vaccines were introduced for routine immunization in the United Kingdom and the Republic of Ireland in 1992. Coincident with this, active prospective and national surveillance via pediatricians, microbiologists, and public health physicians was commenced to assess the clinical and immunological factors associated with vaccine failure. During the 6 years of the study, 115 children with true vaccine failure were reported. Of the children who were vaccinated before 12 months of age, a clinical risk factor was detected in 20%, an immunological deficiency was detected in 30%, and one or both were detected in 44%. Children who were vaccinated after 12 months of age were more likely to have one or both factors (67%). Thirty percent (33 of 105) of children with true vaccine failure had a low Hib antibody response (concentration, <1.0 microg/mL) after disease, but the majority then responded to a further dose of Hib vaccine. Children who develop Hib disease despite vaccination deserve further clinical and immunological evaluation.

Haemophilus influenzae type b disease and vaccination in Europe: lessons learned

OBJECTIVE

To scrutinize the experiences of those European countries that have played a central role in understanding the behavior of and vaccination for Haemophilus influenzae type b (Hib) diseases, to enlighten weaknesses and to explore whether lessons learned would benefit other countries in combating Hib.

DESIGN

Epidemiologic and clinical data on Hib infections and vaccinations were analyzed, including all disease manifestations and all age groups. To improve reliability, sources that used active case finding were especially searched for.

RESULTS

In the prevaccination era meningitis represented 40 to 70% of all classical Hib diseases. Epiglottitis was the second most common presentation, except in southern Europe (data not available from former socialist countries). The overall incidence of meningitis and of all Hib disease combined for children ages 0 to 4 years was 23 and 41 per 100000, suggesting 9900 and 17800 cases per year, respectively. Including all age groups and entities, >20000 Hib cases occurred annually. Vaccination, accomplished with two or three primary doses and a late booster, has almost eliminated Hib disease in >10 countries, and >10000 cases per year are prevented. An age analysis of Hib meningitis suggests that strong early immunogenicity is not as imperative in Europe as in some other regions. The incidence of non-type b H. influenzae infections has not increased.

CONCLUSIONS

With Hib epidemiology comparable with that in Europe, good protection is achieved by various conjugate vaccines also with two primary doses only. However, active research on the whole Hib issue should be a priority, especially in southern and eastern European countries.

Invasive Haemophilus influenzae in the Republic of Ireland

Prior to the general availability of Haemophilus influenzae type b vaccine in the Republic of Ireland, a two-year study of the epidemiology of invasive Haemophilus influenzae disease was carried out. Of 137 invasive strains of Haemophilus influenzae examined in a central laboratory, 94.2% were serotype b and 90.5% were biotype I. Seventeen percent of serotype b strains produced beta-lactamase, and 2.3% were resistant to both ampicillin and chloramphenicol. The majority of serotype b strains were electrophoretic types of the electrophoretic 12 clone family, principally 12.5. Meningitis was the most common infection caused by serotype b. The study data extend the current knowledge of strains of Haemophilus influenzae causing invasive disease in the Republic of Ireland.

Haemophilus influenzae: then and now

Haemophilus influenzae has long been recognised as a major cause of serious infection and mortality in children less than 5 years old. Prior to the introduction of Haemophilus influenzae type b (Hib) immunisation, the incidence of a child suffering an invasive Haemophilus infection was 20-50/100,000 in industrialised countries and up to ten times higher in developing regions. The introduction of a Hib vaccine programme results in a rapid and dramatic decline in the incidence of Hib infection in the susceptible childhood population. For example, within two years of the introduction of routine Hib vaccination of infants in the UK, the risk of serious Hib infection had fallen from 1:600 to 1:30,000 by 5 years of age. Many other European countries have introduced, or are in the process of introducing, a routine Hib immunisation programme. Because the epidemiology of Haemophilus influenzae infection is changing so dramatically, it is opportune to review Haemophilus influenzae as it was perceived in the pre-vaccine era (the past) and during vaccine implementation (the present), and how its role may change in the post-vaccination era (the future). This review will summarise the historical landmarks that have led to our present-day understanding of Haemophilus influenzae pathogenicity, the concerns about antibiotic resistance, the features of the host immune response to Haemophilus influenzae, and the introduction of the Hib vaccine. Furthermore, the possible importance of this organism in the future will be discussed.

Acute haematogenous osteomyelitis--evaluation of management in the 1990s

There are three main areas of debate in the management of acute haematogenous osteomyelitis: The value of early operative intervention, the duration and route of antibiotic treatment and the choice of antibiotic therapy. The aim of this study is to evaluate the management protocol of acute haematogenous osteomyelitis as used in The Childrens' Hospital, Temple Street. The protocol can be recommended. Absence of pyrexia and a normal Erythrocyte Sedimentation Rate do not exclude acute haematogenous osteomyelitis. Current thoughts on antimicrobial therapy are presented.