Epidemiology of invasive Haemophilus influenzae infections in Cape Town, South Africa

A Systematic Review and Meta-analysis of Sex Differences in Morbidity and Mortality of Acute Lower Respiratory Tract Infections Among African Children

Context

Although biological sex influences Acute Lower Respiratory Tract Infections (ALRIs) morbidity and mortality patterns in children living in sub-Saharan Africa, the exact mechanism about the effect is unknown.

Objective

We assessed the quality and strength of evidence on the association of sex with incidence, etiology, and outcomes of ALRI in African children.

Data Sources Study Selection and Data Extraction

We systematically searched electronic databases for publications from 1971-2016 in PubMed, African Journals Online, and Google scholar for ALRI literature in the African children. We used (pneumonia OR bronchiolitis OR "community-acquired pneumonia" OR CAP OR "hospital-acquired pneumonia" OR "nosocomial pneumonia" OR "ventilator-acquired pneumonia" OR "lung abscess" OR "pleural effusion" OR "empyema thoracis") AND (sex OR gender) AND (Africa OR Sub-Saharan) as search terms. We included the published peer-reviewed journal articles reporting on incidence, etiology, and case fatality. We summarized the findings using narrative and meta-analysis methods.

Results

We included 14 studies with sex-related data; the median (IQR) number of reported pneumonia cases was 148 (87-770) and 114 (56-599) for male and female patients, respectively. Only two studies reported a sex-specific incidence. The odds of sex were in favor of male sex, and the chances of identification of Respiratory Syncytia Virus (RSV) were significantly lower in males than in females (OR=0.60; 95% CI: 0.42, 0.86). Estimates from 9 studies showed that the death rate for males was significantly higher than for females (OR=1.26; 95% CI=1.20-1.33).

Conclusions

Sex-disaggregated data on incidence, etiology, and case fatality of pneumonia are scarcely reported in studies published in Africa. However, males appear to die more often than females, and females more likely to have RSV infection.

Circulating innate and adaptive immunity against anti-Haemophilus influenzae type b

Haemophilus influenzae type b (Hib) are one of most dangerous microbes that occupies the paediatric nasopharyngeal as a commensal opportunistic bacterium, which may lead to meningitis in uncontrolled infection. Colonisation of pharyngeal tissues is the starting point for most H. influenzae infections, which may develop into invasive diseases, such meningitis. The vaccination against Hib in specific, as well as against most of vaccines preventable diseases; in general, play a major role in reducing children (< 5 years old) Hib meningitis from 57/100,000 to the lowest known Hib meningitis incidents in the history. First invented Hib vaccine was licensed in 1985 and contained Hib capsular polysaccharide (CPS); afterward, conjugate vaccines have been innovated and licensed on the road to improve Hib vaccine efficacy. Polyribosylribitol phosphate (PRP) is the main vaccine unite structure. Since anti-CPS antibodies in the serum reflect the extent of the acquired immunity against Hib infections, the concentration of ⩾ 0.15 g/ml of anti-CPS is believed to be an indicator for short-term protection from invasive Hib diseases, whereas one-month post-completion of primary Hib immunization concentration of ⩾ 1.0 g/ml is trusted to be immunological protective. As considered that serum anti-CPS antibodies are effectively linked to protection, the evaluation of antibodies concentration and reconsideration of published worldwide populations antibodies concentration are consider vital strides on the way to accurate valuation of Hib immunity that induced by vaccination; either direct or herd. As documented, some populations; worldwide, still susceptible to invasive Hib infections. Several populations worldwide remain vulnerable to Hib-related infections. We believe that up-to-date review article regarding circulated Hib immunology, represented in anti-Hib antibodies and worldwide Hib incidences will provide a precious information for microbiologists, public health officials, epidemiologists, immunologists, and strategic preventive healthcare executives.

Epidemiology of community-acquired pneumonia and implications for vaccination of children living in developing and newly industrialized countries: A systematic literature review

This systematic review evaluated the epidemiology of community-acquired pneumonia in children <6 y of age within 90 developing and newly industrialized countries. Literature searches (1990–2011), based on MEDLINE, EMBASE, Cochrane, CAB Global Health, WHO, UNICEF, country-specific websites, conferences, health-technology-assessment agencies, and the reference lists of included studies, yielded 8,734 records; 62 of 340 studies were included in this review. The highest incidence rate among included studies was 0.51 episodes/child-year, for children <5 y of age in Bangladesh. The highest prevalence was in Chinese children <6 months of age (37.88%). The main bacterial pathogens were Streptococcus pneumoniae, Haemophilus influenzae and Mycoplasma pneumoniae and the main viral pathogens were respiratory syncytial virus, adenovirus and rhinovirus. Community-acquired pneumonia remains associated with high rates of morbidity and mortality. Improved and efficient surveillance and documentation of the epidemiology and burden of community-acquired pneumonia across various geographical regions is warranted.

Haemophilus influenzae serotype a as a cause of serious invasive infections

Haemophilus influenzae, particularly H influenzae serotype b (Hib), is an important pathogen that causes serious diseases like meningitis and septicaemia. Since the introduction of Hib conjugate vaccines in the 1990s, the epidemiology of invasive H influenzae disease has changed substantially, with most infections now caused by non-Hib strains. We discuss the importance of H influenzae serotype a (Hia) as a cause of serious morbidity and mortality and its global epidemiology, clinical presentation, microbiology, immunology, prevention, and control. Much like Hib, the capsule of Hia is an important virulence factor contributing to the development of invasive disease. Molecular typing of Hia has identified distinct clonal groups, with some linked to severe disease and high case-fatality rates. Similarities between Hia and Hib capsules, their clinical presentation, and immunology of infection suggest that a bivalent Hia-Hib capsular polysaccharide-protein conjugate vaccine could offer protection against these two important serotypes of H influenzae.

Haemophilus influenzae type b conjugate vaccines - a South African perspective

Introduction of Hib vaccine is known to positively impact on reduction of both morbidity and mortality in children less than 5 years of age. Incorporation of this vaccine into a National EPI, however, does come at a significant cost, which is especially important in non-GAVI funded countries. Compounded reduction in response in certain patient populations and possible indication of booster doses further impacts on cost-benefit analyses. Despite these issues, South Africa has supplied Hib vaccine as part of the National EPI in the form of a combination vaccine, Pentaxim, which combines Hib with Diphtheria, Tetanus, acellular Pertussis (DTP) and Poliomyelitis since 2009. Prior to this, another combination vaccine was utilized containing Hib and DTP. This has subsequently lead to a significant reduction in invasive Hib disease post-introduction, therefore largely justifying utilization.

Etiology of meningitis among patients admitted to a tertiary referral hospital in Botswana

This retrospective review evaluated records of cerebrospinal fluid samples between 2000 and 2008 at Princess Marina Hospital in Gaborone, Botswana. Of the 7501 cerebrospinal fluid samples reviewed, Streptococcus pneumoniae (n = 125) and Haemophilus influenzae (n = 60) were the most common bacteria cultured. There were also 1018 cryptococcal and 44 tuberculous meningitis cases. Antimicrobial susceptibilities are described. Public health interventions could decrease the burden of meningitis in Botswana.

The Elimination of Haemophilus influenzae type b meningitis following conjugate vaccine introduction in Senegal

BACKGROUND

Senegal introduced routine infant Haemophilus influenzae type b (Hib) conjugate vaccine during 2005.

METHODS

We evaluated acute bacterial meningitis surveillance data among children 0 to 59 months of age collected during January 2003 to September 2007 at the major pediatric referral hospital in the Dakar Region of Senegal. Hib vaccine effectiveness was assessed using a case-control design.

RESULTS

A total of 1749 children with suspected bacterial meningitis were included in the current study of whom 142 (8%) had Hib identified. Among children less than age 1 year, the average annual Hib meningitis incidence decreased from 22 to 47 per 100,000 during 2003-2005 to 1.4 per 100,000 during 2007, while pneumococcal meningitis incidence remained stable. Before vaccine introduction, calculated incidences varied over 4-fold between districts within the Dakar Region for the years 2003 to 2005. Following use of Hib vaccine, pneumococcus has now become the most common etiology of pediatric acute bacterial meningitis in Dakar region.

CONCLUSIONS

Senegal successfully implemented Hib conjugate vaccine into their routine infant immunization program with a resultant near elimination of Hib meningitis burden.

Meningitis registry of hospitalized cases in children: epidemiological patterns of acute bacterial meningitis throughout a 32-year period

Background

Bacterial meningitis remains a source of substantial morbidity and mortality in childhood. During the last decades gradual changes have been observed in the epidemiology of bacterial meningitis, related to the introduction of new polysaccharide and conjugate vaccines. The study presents an overview of the epidemiological patterns of acute bacterial meningitis in a tertiary children 's hospital during a 32-year period, using information from a disease registry. Moreover, it discusses the contribution of communicable disease registries in the study of acute infectious diseases.

Methods

In the early 1970s a Meningitis Registry (MR) was created for patients admitted with meningitis in Aghia Sofia Children's Hospital in Athens. The MR includes demographic, clinical and laboratory data as well as treatment, complications and outcome of the patients. In 2000 a database was created and the collected data were entered, analyzed and presented in three chronological periods: A (1974–1984), B (1985–1994) and C (1995–2005).

Results

Of the 2,477 cases of bacterial meningitis registered in total, 1,146 cases (46.3%) were classified as "probable" and 1,331 (53.7%) as "confirmed" bacterial meningitis. The estimated mean annual Incidence Rate (IR) was 16.9/100,000 for bacterial meningitis, 8.9/100,000 for Neisseria meningitidis, 1.3/100,000 for Streptococcus pneumoniae, 2.5/100,000 for Haemophilus influenzae type b (Hib) before vaccination and 0.4/100,000 for Hib after vaccination. Neisseria meningitis constituted the leading cause of childhood bacterial meningitis for all periods and in all age groups. Hib was the second most common cause of bacterial meningitis before the introduction of Hib conjugate vaccine, in periods A and B. The incidence of bacterial meningitis due to Streptococcus pneumoniae was stable. The long-term epidemiological pattern of Neisseria meningitidis appears in cycles of approximately 10 years, confirmed by a significant rise of IR in period C. The Case Fatality Rate (CFR) from all causes was 3.8%, while higher CFR were estimated for Streptococcus pneumoniae (7.5%, RR=2.1, 95% CI 1.2–3.7) and Neisseria meningitidis (4.8%, RR=1.7, 95% CI 1.1–2.5) compared to other pathogens. Moreover, overall CFR varied significantly among the three time periods (p = 0.0015), and was estimated to be higher in period C.

Conclusion

By using the MR we were able to delineate long-term changes in the epidemiology of bacterial meningitis. Thus the MR proved to be a useful tool in the study and the prevention of communicable diseases in correlation with prevention strategies, such as vaccinations.

Introduction of Haemophilus influenzae type B conjugate vaccine into routine immunization in Ghana and its impact on bacterial meningitis in children younger than five years

This report shows the impact of a pentavalent vaccine that includes Haemophilus influenzae type b (Hib) conjugate vaccine on bacterial meningitis in children younger than 5 years in Ghana. A review of the first 3 years of a pediatric bacterial meningitis surveillance program, started in August 2001 in Accra, Ghana, was undertaken. There was a significant reduction, P = 0.042 and 0.017, in percentage of purulent meningitis in children younger than 1 year, comparing the first year when the vaccine was introduced, to the second and third years, respectively.

The impact of routine infant immunization with Haemophilus influenzae type b conjugate vaccine in Malawi, a country with high human immunodeficiency virus prevalence

Malawi has extreme poverty and a high-human immunodeficiency virus (HIV) prevalence. Following Haemophilus influenzae type b (Hib) conjugate vaccine introduction during 2002, we evaluated vaccine impact by reviewing hospital surveillance data for acute bacterial meningitis in Blantyre district among children age 1-59 months admitted during 1997-2005. Documented annual Hib meningitis incidence rates decreased from 20-40/100,000 to near zero among both rural and urban residents despite no change in pneumococcal meningitis incidence rates. Before vaccine introduction, an average of 10 children/year had Hib meningitis and HIV infection compared to 2/year during 2003-2004 and none during 2005. Vaccine effectiveness was high following two or more doses of vaccine. The most urgent future need is for a sustainable routine infant immunization program, including a less expensive vaccine that preferably is delivered in a multivalent form.

Effectiveness of Haemophilus influenzae type b Conjugate vaccine introduction into routine childhood immunization in Kenya

CONTEXT

Haemophilus influenzae type b (Hib) conjugate vaccine is not perceived as a public health priority in Africa because data on Hib disease burden and vaccine effectiveness are scarce. Hib immunization was introduced in Kenyan infants in 2001.

OBJECTIVE

To define invasive Hib disease incidence and Hib vaccine program effectiveness in Kenya.

DESIGN, SETTING, AND PATIENTS

Culture-based surveillance for invasive Hib disease at Kilifi District Hospital from 2000 through 2005 was linked to demographic surveillance of 38,000 children younger than 5 years in Kilifi District, Kenya. Human immunodeficiency virus (HIV) infection and Hib vaccination status were determined for children with Hib disease admitted 2002-2005.

INTERVENTIONS

Introduction of conjugate Hib vaccine within the routine childhood immunization program at ages 6, 10, and 14 weeks beginning November 2001.

MAIN OUTCOME MEASURES

Incidence of culture-proven Hib invasive disease before and after vaccine introduction and vaccine program effectiveness.

RESULTS

Prior to vaccine introduction, the median age of children with Hib was 8 months; case fatality was 23%. Among children younger than 5 years, the annual incidence of invasive Hib disease 1 year before and 1 and 3 years after vaccine introduction was 66, 47, and 7.6 per 100,000, respectively. For children younger than 2 years, incidence was 119, 82, and 16 per 100,000, respectively. In 2004-2005, vaccine effectiveness was 88% (95% confidence interval, 73%-96%) among children younger than 5 years and 87% (95% confidence interval, 66%-96%) among children younger than 2 years. Of 53 children with Hib admitted during 2002-2005, 29 (55%) were age-ineligible to have received vaccine, 12 (23%) had not been vaccinated despite being eligible, and 12 (23%) had received 2 or more doses of vaccine (2 were HIV positive).

CONCLUSIONS

In Kenya, introduction of Hib vaccine into the routine childhood immunization program reduced Hib disease incidence among children younger than 5 years to 12% of its baseline level. This impact was not observed until the third year after vaccine introduction.

The epidemiology of Haemophilus influenzae type b meningitis in Burkina Faso

BACKGROUND

Haemophilus influenzae type b (Hib) disease burden studies are important to conduct in African countries that plan to introduce vaccine so that vaccine impact can be documented.

METHODS

We implemented population-based meningitis surveillance in 3 districts of Burkina Faso for 12 months each during 2002-2003 and 2004-2005 using polymerase chain reaction, culture and antigen detection.

RESULTS

Lumbar puncture was performed on 1686 patients and 112 had Hib identified. Persons <1, <5, 5-14 and 15+ years of age had annual Hib meningitis incidences of 97, 34, 2.1 and 0.55 per 100,000, respectively; overall case fatality proportion was 25%. During the historic meningitis epidemic season months of December through April, the proportion of purulent cerebrospinal fluid among children aged <5 years that yielded Hib was 27% compared with 30% during other months. Twenty-five of 98 persons with information available were treated with only one or 2 doses of oily chloramphenicol. Among children age <5 years with Hib meningitis, 28% were pretreated with antimalarials and antimalarial pretreatment was associated with delay in hospitalization.

CONCLUSIONS

In Burkina Faso, Hib meningitis incidence and case fatality proportion are high and thus vaccine could have a substantial impact. While awaiting well-implemented routine infant Hib vaccination, empiric case management for pediatric meningitis in sub-Saharan Africa must recognize that Hib is likely even during the epidemic season. In malaria-endemic areas, pediatric Hib meningitis case management may be adversely affected by the similar presentation of these 2 diseases.

Immunogenicity and effectiveness of Haemophilus influenzae type b conjugate vaccine in HIV infected and uninfected African children

The quantitative (anti-Hib capsular polysaccharide antibody concentrations; anti-HibPS) and qualitative (bactericidal activity and avidity) aspects in immune responses to Haemophilus influenzae type b polyribosyl ribitol phospshate-CRM(197) conjugate vaccine (HibCV; HibTiter) were evaluated in 66 HIV infected children not receiving anti-retroviral therapy and 127 HIV uninfected children. Surveillance was conducted for invasive Hib disease in a cohort of 39,865 (approximately 6.4% of whom were HIV infected) children from March 1998 to June 2004. HIV infected children had lower anti-HibPS geometric mean antibody concentrations 1 month post-immunisation than HIV uninfected children (P<0.00001) and were less likely to have anti-HibPS antibody concentrations of >or=1.0 microg/ml (RR 0.54; 95% CI 0.43-0.69). A lower proportion of HIV infected children than HIV uninfected children (RR 0.78; 95% CI 0.66-0.93) had measurable anti-Hib serum bactericidal activity (SBA) and the HibPS antibody concentration required for 50% killing of Hib bacteria was greater among HIV infected than HIV uninfected children (P=0.001). The estimated risk of HibCV failure was 35.1-fold greater (95% CI 14.6-84.6) amongst HIV infected than HIV uninfected children.

Incidences of vaccine-preventable Haemophilus influenzae type b pneumonia and meningitis in Indonesian children: hamlet-randomised vaccine-probe trial

BACKGROUND

Most studies of Haemophilus influenzae type b (Hib) disease in Asia have found low rates, and few Asian countries use Hib vaccine in routine immunisation programmes. Whether Hib disease truly is rare or whether many cases remain undetected is unclear.

METHODS

To estimate incidences of vaccine-preventable Hib pneumonia and meningitis among children younger than 2 years in Lombok, Indonesia, during 1998-2002, we undertook a hamlet-randomised, controlled, double-blind vaccine-probe study (818 hamlets). Children were immunised (WHO schedule) with diphtheria, tetanus, pertussis (DTP) or DTP-PRP-T (Hib conjugate) vaccine. Vaccine-preventable disease incidences were calculated as the difference in rates of clinical outcomes between DTP and DTP-PRP-T groups. Analyses included all children who received at least one vaccine dose.

FINDINGS

We enrolled 55073 children: 28147 were assigned DTP-PRP-T and 26926 DTP. The proportion of pneumonia outcomes prevented by vaccine ranged from less than 0 to 4.8%. Calculated incidences of vaccine-preventable Hib disease (per 10(5) child-years of observation) for outcome categories were: substantial alveolar consolidation or effusion, less than zero (-43 [95% CI -185 to 98]); all severe pneumonia, 264 (95% CI less than zero to 629); all clinical pneumonia, 1561 (270 to 2853); confirmed Hib meningitis, 16 (1.4 to 31); meningitis with cerebrospinal-fluid findings consistent with a bacterial aetiology, 67 (22 to 112); and admission for suspected meningitis or presenting to a clinic with convulsions, 158 (42 to 273).

INTERPRETATION

Hib vaccine did not prevent the great majority of pneumonia cases, including those with alveolar consolidation. These results do not support a major role for Hib vaccine in overall pneumonia-prevention programmes. Nevertheless, the study identified high incidences of Hib meningitis and pneumonia; inclusion of Hib vaccine in routine infant immunisation programmes in Asia deserves consideration.

Acute bacterial meningitis in children admitted to a rural Kenyan hospital: increasing antibiotic resistance and outcome

BACKGROUND

Acute bacterial meningitis (ABM) is an important cause of mortality in Africa, but most studies are based in urban referral hospitals. Poor laboratory facilities make diagnosis difficult, and treatment is limited to inexpensive antibiotics.

METHODS

We retrospectively reviewed data from children admitted with ABM to a Kenyan district hospital from 1994 through 2000. We calculated the minimum incidence in children admitted from a defined area. We also examined the antibiotic susceptibility patterns.

RESULTS

We identified 390 cases (1.3% of all admissions) of whom 88% were <5 years old. The apparent minimum annual incidence in children younger than 5 years of age increased from 120 to 202 per 100,000 between 1995 and 2000 (P < 0.001). Increasing the lumbar punctures performed by including prostrated or convulsing children significantly increased the number of cases detected (P < 0.005). The most common organisms in infants <3 months were streptococci and Enterobacteriaceae. Streptococcus pneumoniae (43.1%) and Haemophilus influenzae (41.9%) were predominant in the postneonatal period. The overall mortality was 30.1%, and 23.5% of survivors developed neurologic sequelae. Chloramphenicol resistance of H. influenzae rose from 8% in 1994 to 80% in 2000 (P < 0.0001) accompanied by an apparent increase in mortality. A short history, impaired consciousness and hypoglycemia were associated with death. Prolonged coma and low cerebrospinal fluid glucose were associated with neurologic sequelae.

CONCLUSION

ABM in rural Kenya is a severe illness with substantial mortality and morbidity. Prognosis could be improved by broadening the criteria for lumbar puncture and use of appropriate antibiotics.

Are Haemophilus influenzae infections a significant problem in India? A prospective study and review

It has been suggested Haemophilus influenzae serotype b (Hib) disease is uncommon in Asia. During 1993--1997, we conducted prospective surveillance of acute infections caused by H. influenzae in 6 academic referral Indian hospitals. The study included 5798 patients aged 1 month to 50 years who had diseases likely to be caused by H. influenzae; 75% of the patients were aged <5 years. A total of 125 H. influenzae infections were detected, 97% of which were caused by Hib. Of 125 isolates, 108 (86%) were from children aged <5 years, and 11 (9%) were from adults aged >18 years. Sixty-two percent of the patients had meningitis. The case-fatality rate was 11% overall and 20% in infants with Hib meningitis. Up to 60% of all isolates were resistant to chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, or erythromycin; 32% were resistant to >/= 3 antimicrobial drugs, but none were resistant to third-generation cephalosporins. These data suggest that available Hib vaccines will benefit Indian children.

Cost-benefit analysis of a Haemophilus influenzae type b meningitis prevention programme in The Philippines

BACKGROUND

Haemophilus influenzae type b (Hib) meningitis is associated with high mortality and serious sequelae in children under 5 years of age. Vaccines which can prevent this infection are available.

OBJECTIVE

To evaluate the costs and benefits of a 3-dose immunisation schedule in Manila, Philippines.

PERSPECTIVE

Government and societal perspectives.

DESIGN AND PARTICIPANTS

A cost-benefit analysis based on a birth cohort of 100,000 children. The state of health of the cohort with and without a Hib immunisation programme was modelled over a 5-year period. A survey of medical records of patients with Hib in Manila provided data on the extent and cost of sequelae following infection.

INTERVENTION

A 3-dose Hib vaccination programme given at ages 2, 3 and 4 months.

RESULTS

The model predicted that vaccinating children against Hib meningitis would prevent 553 cases per year in a birth cohort of 100,000, at a cost of 56,200 Philippine pesos (PHP) [$US1,605; 1998 exchange rate] per case (base case assumptions of 90% vaccine efficacy rate, 95 per 100,000 Hib incidence rate, 85% vaccination coverage). Results from the cost-benefit analyses indicated that the saving to the government would be around PHP39 million ($US1.11 million), and the saving to society would be PHP255 million ($US7.28 million).

CONCLUSION

There would be a positive economic benefit for the Philippine government and for the Filipino society if a Hib vaccination programme was introduced in Manila.

Burden of meningitis and other severe bacterial infections of children in africa: implications for prevention

Apart from meningococcal disease in the sub-Saharan meningitis belt, the incidence and impact of life-threatening bacterial diseases in children across Africa have not been quantified. The clinical and epidemiological data on pneumococcal, Haemophilus influenzae type b (Hib), and other forms of bacterial meningitis, as well as data on other severe bacterial infections throughout the continent were scrutinized. Pneumococci were the leading causative agents of nonepidemic meningitis and other bacteremic diseases, followed by Hib. Meningococcal diseases were less common. Mortality rates associated with pneumococcal, Hib, and meningococcal meningitis were 549 (45%) of 1211 patients, 389 (29%) of 1352 patients, and 104 (8%) of 1236 patients, respectively; sequelae occurred in 50%, 40%, and 10% of cases. At 0-4 years of age, the estimated incidences of Hib meningitis and all classic Hib diseases were 70 and 100 cases per 100,000 population per year, accounting for approximately 90,000 and 120,000 cases per year, respectively. Including older age groups and, especially, nonbacteremic Hib pneumonia in the estimates of Hib disease in Africa increased the overall numbers manifold; the numbers of pneumococcal infections were even greater. The only realistic way to combat these severe infections efficaciously would be through widespread vaccination, starting with Hib conjugates.

Worldwide Haemophilus influenzae type b disease at the beginning of the 21st century: global analysis of the disease burden 25 years after the use of the polysaccharide vaccine and a decade after the advent of conjugates

Vaccination against Haemophilus influenzae type b (Hib) diseases began a quarter of a century ago with a polysaccharide vaccine; this vaccine was followed by four different conjugates 10 years later. In this review, the burden of global Hib disease is quantified following this 25-year period of vaccine availability to determine the potential impact of conjugate vaccines. This task was accomplished by analysis of data available in 10 languages in 75 geographical regions of over 50 countries. All severe Hib diseases, not only meningitis, were characterized, and special attention was paid to the most vulnerable age group, i.e., children aged 0 to 4 years. Prior to vaccination, the weighted worldwide incidence of meningitis in patients younger than 5 years was 57/100,000, and for all Hib diseases except nonbacteremic pneumonia, it was 71/100,000, indicating 357,000 and 445,000 cases per year, respectively. At least 108,500 of these children died. For all age groups combined, there were 486,000 cases of Hib disease, excluding pneumonia, with 114,200 deaths and probably an equal number of sequelae per annum. If the figures for nonbacteremic pneumonia are included, a conservative estimate is that over 2.2 million cases of infection and 520,000 deaths from Hib disease occurred worldwide, but the true numbers might have been greater. Despite these large numbers and availability of safe and efficacious vaccines, only 38,000 cases annually are prevented-a meager 8% or less than a 2% reduction in cases, depending on whether nonbacteremic pneumonia is included in the calculations. Although vaccination has had great success in some affluent countries, the current level of activity has had a very small impact globally. The use of conjugates, preferably with a reduced number of doses and in combination with other vaccines or perhaps in fractional doses, should be extended to less privileged countries, where most Hib disease occurs.

Worldwide Haemophilus influenzae type b disease at the beginning of the 21st century: global analysis of the disease burden 25 years after the use of the polysaccharide vaccine and a decade after the advent of conjugates

Vaccination against Haemophilus influenzae type b (Hib) diseases began a quarter of a century ago with a polysaccharide vaccine; this vaccine was followed by four different conjugates 10 years later. In this review, the burden of global Hib disease is quantified following this 25-year period of vaccine availability to determine the potential impact of conjugate vaccines. This task was accomplished by analysis of data available in 10 languages in 75 geographical regions of over 50 countries. All severe Hib diseases, not only meningitis, were characterized, and special attention was paid to the most vulnerable age group, i.e., children aged 0 to 4 years. Prior to vaccination, the weighted worldwide incidence of meningitis in patients younger than 5 years was 57/100,000, and for all Hib diseases except nonbacteremic pneumonia, it was 71/100,000, indicating 357,000 and 445,000 cases per year, respectively. At least 108,500 of these children died. For all age groups combined, there were 486,000 cases of Hib disease, excluding pneumonia, with 114,200 deaths and probably an equal number of sequelae per annum. If the figures for nonbacteremic pneumonia are included, a conservative estimate is that over 2.2 million cases of infection and 520,000 deaths from Hib disease occurred worldwide, but the true numbers might have been greater. Despite these large numbers and availability of safe and efficacious vaccines, only 38,000 cases annually are prevented-a meager 8% or less than a 2% reduction in cases, depending on whether nonbacteremic pneumonia is included in the calculations. Although vaccination has had great success in some affluent countries, the current level of activity has had a very small impact globally. The use of conjugates, preferably with a reduced number of doses and in combination with other vaccines or perhaps in fractional doses, should be extended to less privileged countries, where most Hib disease occurs.

Epidemiology of Haemophilus influenzae type b meningitis in Manila, Philippines, 1994 to 1996

BACKGROUND

Effective vaccines against Haemophilus influenzae type b (Hib) have shown impressive results in decreasing Hib meningitis in developed countries. In the Philippines Hib vaccines are not part of the routine immunization given to children. Before a decision can be made to include Hib vaccines in immunization program, epidemiology of Hib meningitis in Manila, Philippines, should first be described.

METHODOLOGY

A cohort of 41,592 children <5 years of age in Central Manila was the study population. Confirmed cases between January, 1994, and December, 1996, were obtained from all hospitals in the region. Confirmation of cases was based on positive culture isolated from blood or cerebrospinal fluid (CSF) or Hib antigen identified in CSF with a clinical diagnosis of Hib meningitis. The progress of children with Hib meningitis postinfection was evaluated from hospital records.

RESULTS

There were 118 episodes of Hib meningitis identified in the population in the study period. Sequelae occurred in 15% of the total cases, and the case fatality rate was 11%. The annual incidence of Hib meningitis in Manila for children <5 years old was 95 per 100,000.

CONCLUSIONS

Hib meningitis in Central Manila is common. The incidence is particularly high in children <6 months old. Adverse neurologic outcomes and a high case fatality rate in children younger than 1 year suggest that a vaccination program would be useful.

Policy analysis of the use of hepatitis B, Haemophilus influenzae type b-, Streptococcus pneumoniae-conjugate and rotavirus vaccines in national immunization schedules

After the development of national vaccine programmes to deliver six vaccines to infants, new vaccine adoption has been limited. Analysis of the health and economic implications of new vaccination options can help national policy-makers. Country specific quantitative policy analyses were conducted to estimate the impact of vaccination against hepatitis B (HB), Haemophilus influenzae type b (Hib), Streptococcus pneumoniae (SP) and rotavirus. Disease burden, programme costs and the potential reduction of disease from vaccination was assessed for each vaccine. Without vaccination, these four vaccine preventable diseases contribute up to 4.1 million deaths in each successive birth cohort. Routine scheduled use of HB and Hib vaccines could prevent up to 1.7 million deaths; SP and rotavirus vaccines, an additional 1.4 million deaths, annually. The global cost per life-year saved ranged from $29 to $150 with great variation by income and economic groups. With a few exceptions for a few countries, these vaccines would cost a fraction of average per-capita gross domestic product to save a life-year. The addition of HB and Hib vaccines, should be considered for integration in all national immunization programmes. SP and rotavirus vaccines, with the given assumptions, would also be cost-effective. Proactive analysis of the economic and epidemiologic impact of these vaccines can hasten their introduction into national vaccination schedules.

Acute lower respiratory tract infections in children in Kuwait

The features of community-acquired acute lower respiratory tract infections in 390 children are described. Half (50%) presented with bronchiolitis, 37% with pneumonia and 13% with croup. Respiratory syncytial virus was the commonest agent identified (52% of bronchiolitis, 29% of pneumonia, 51% of croup). Positive bacterial blood cultures were obtained in 10% of the patients, all except one with pneumonia. Fever (> 39 degrees C), a toxic ill look, bronchial breathing, WCC > 20 x 10(9)/l, neutrophils > 5 x 10(9)/l, platelet count > 500 x 10(9)/l, ESR > 45 mm/hr, lobar consolidation and pleural effusion were more likely to be associated with bacterial than with viral pneumonia (relative risk > 1.81; p < 0.05). In areas with limited resources, a high fever, a toxic ill look, bronchial breathing and simple laboratory tests may help to identify patients with bacterial pneumonia.

Haemophilus influenzae type b disease in the western region of The Gambia: background surveillance for a vaccine efficacy trial

In preparation for a field trial of an Haemophilus influenzae type b conjugate vaccine in the Western Region of The Gambia, a 3-year prospective study was undertaken to determine the incidence of Hib disease and the vaccination status of affected children. One hundred and eighty-two children with invasive Hib disease were found; 141 (77%) had meningitis, 31 (17%) pneumonia and 10 (6%) other forms of invasive disease. The estimated annual incidence rates for all invasive Hib diseases were 274 and 73 per 100,000 in children aged < 1 and < 5 years, respectively. For meningitis, the rate was 222 per 100,000 per year in children aged < 1 year. Children with meningitis were significantly younger than those with pneumonia (median age 7 months, interquartile range [IQR] 5-9, vs 12 months, IQR 6-15 (P = 0.002)) and younger than those with other forms of Hib disease. Of 142 children for whom vaccination status was known, 18 had received no DPT, 36 had received one, 40 had received two and 48 had received three doses. This study confirmed the high incidence of systemic Hib disease among Gambian children and the need to vaccinate at an early age. It provided the background epidemiological data required for the successful planning of an Hib vaccine trial which is now in progress.