Clear and present danger: in childhood meningitis. The importance of Hib immunisation in infancy and high-risk groups.

The incidence of Haemophilus influenzae type b (Hib) invasive disease has declined significantly in the United Kingdom since the introduction of routine Hib immunisation. However life-threatening Hib infections such as meningitis and epiglottitis may still occur, especially in the unimmunised and immigrant children. A case of Hib meningitis is a reminder that the threat of invasive Hib disease has not been totally eliminated. Early diagnosis and treatment of bacterial meningitis (including Hib meningitis) is essential to prevent death and serious neurological sequelae. Health visitors play a vital role in encouraging parents to have their children immunised without any avoidable delays and in providing reliable information as necessary to back up this advice. Enquiring about immunisation status of all children new to a practice and addressing any omissions, should be routine; immigrant children (and their parents) may be particularly vulnerable and more likely to be inadequately immunised.

The Alaska Haemophilus influenzae type b experience: lessons in controlling a vaccine-preventable disease.

OBJECTIVE: Before 1991, Alaska Native children experienced one of the highest rates of invasive Haemophilus influenzae type b disease. H influenzae type b vaccine has led to a near-elimination of invasive H influenzae type b disease in the United States. We describe challenges encountered in controlling H influenzae type b disease in Alaska and update the current status of H influenzae disease and carriage in Alaska as lessons to other populations. PATIENTS AND METHODS: We reviewed data from statewide H influenzae disease surveillance conducted during 1980-2004. Vaccine coverage data were based on audits from tribal facilities and the National Immunization Survey. H influenzae type b colonization data were based on 6 carriage studies. RESULTS: After universal infant vaccination in 1991, H influenzae type b disease among Alaska Native and non-Native children < 5 years of age decreased by 94% and 96%, respectively. After a 1996 change in H influenzae type b vaccine from polyribosylribitol phosphate-outer membrane protein conjugate vaccine to H influenzae type b oligosaccharide-CRM197 vaccine, the incidence of H influenzae type b disease increased in rural Alaska Natives from 19.8 to 91.1 cases per 100000 per year < 5 years of age. During 2001-2004, with use of polyribosylribitol phosphate-outer membrane protein conjugate vaccine, the rate of H influenzae type b disease in Alaska Native and non-Native children aged < 5 years decreased to 5.4 and 0 per 100000 per year, respectively. In postvaccine studies, H influenzae type b carriage has decreased in Alaska Native children < 5 years of age. CONCLUSIONS: H influenzae type b vaccination has resulted in a dramatic decrease in invasive H influenzae type b disease in Alaska; however, despite high rates of H influenzae type b vaccine coverage, H influenzae type b disease rates among rural Alaska Native children < 5 years of age remain higher than the rates among non-Native Alaska and other US children. Equity in disease rates may not be achieved in indigenous populations with the current vaccines unless other environmental and household factors contributing to disease transmission are addressed.

Prospective study of bacterial meningitis in North East Thames region, 1991-3, during introduction of Haemophilus influenzae vaccine.

OBJECTIVE: To describe the epidemiology of primary bacterial meningitis in the North East Thames region over a three year period before and during the introduction of the vaccine for Haemophilus influenzae type b. DESIGN: Analysis of information on cases of primary bacterial meningitis identified by microbiology laboratories in the region, with collection of case data by questionnaire. MAIN OUTCOME MEASURES: Annual incidence rates for types of meningitis according to age and ethnic group. RESULTS: The annual incidence rates for the three major causes of bacterial meningitis in the general population were 1.9/100,000 for Neisseria meningitidis, 1.6/100,000 for Haemophilus influenzae before vaccination, and 1.0/100,000 for Streptococcus pneumoniae. Higher rates of H influenzae meningitis were found in Asians compared with white people (3.6/100,000 v 1.5/100,000, P = 0.01). As a result of the vaccine programme introduced in October 1992 the number of cases of H influenzae meningitis in children under 5 years has fallen by 87%. CONCLUSIONS: Bacterial meningitis is a serious problem especially in preschool children. There are differences in the incidence of some causes of bacterial meningitis in different ethnic groups; with H influenzae type b being significantly more common among black and Asian people than among white people. The immunisation programme for H influenzae type b in the North East Thames region has been successful in reducing the incidence of this type of meningitis in Asian and white populations. The numbers were too small to evaluate in the black population.

Epidemiology of pediatric meningitis caused by Haemophilus influenzae B, Streptococcus pneumoniae and Neisseria meningitidis in Israel.

Bacterial meningitis remains a serious cause of morbidity and mortality in childhood. We report 3 year data on meningitis caused by Haemophilus influenzae b, Streptococcus pneumoniae and Neisseria meningitidis in Israeli children younger than 13 years of age. The data were obtained prospectively through an active surveillance system involving all 25 centers in which children are hospitalized. A case was defined by: a) culture positive cerebrospinal fluid; or b) positive blood culture with > 10 cells. During the study period, 482 cases of meningitis due to the three organisms were identified. Of these, 58%, 20% and 22% were caused by H. influenzae b, S. pneumoniae and N. meningitidis, respectively. The male/female ratio was 1.5:1. An over-representation of the non-Jewish population was seen only in cases caused by S. pneumoniae. The median age was 11 months and 59% of all cases occurred by the age of 12 months. The median age was 10, 12 and 36 months and the age-specific incidence for children aged 0-4 years was 18.5, 5.3 and 5.2 per 100,000, respectively, for H. influenzae b, S. pneumoniae and N. meningitidis. The chance of being hospitalized with meningitis during the first 5 years of life was estimated at 146.2 per 100,000. Meningitis was seasonal: 59% al all cases occurred during fall and winter and only 18% during summer. A total of 2,097 hospitalization days were required when extrapolated to a population in which 100,000 live births occur yearly. The case fatality rate was 2.2%, 5.9% and 6.3% for H. influenzae b, S. pneumoniae and N. meningitidis, respectively, with a higher fatality in females and non-Jews.

Epidemiology of pediatric meningitis caused by Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis in Israel: a 3-year nationwide prospective study. Israeli Pediatric Bacteremia and Meningitis Group.

In a 3-year nationwide prospective study on pediatric meningitis caused by Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis in Israel, 1258 invasive infections with a known focus were observed. Meningitis was found in 482 (38%): 56%, 16%, and 76% of all infections by H. influenzae type b, S. pneumoniae, and N. meningitidis, respectively. The incidence of meningitis during the first year of life was 67.1, 17.5, and 9.5/100,000 for H. influenzae type b, S. pneumoniae, and N. meningitidis, respectively, and in children < 5 years old it was 18.5, 5.3, and 5.2. Extrapolated for a population in which 100,000 live births occur yearly, 2097 hospital days were required. The case fatality rate was 2.2%, 5.9%, and 6.3% for H. influenzae type b, S. pneumoniae, and N. meningitidis, respectively. Boys were affected significantly more often than girls, but mortality was higher among girls. On the basis of the observed serotypes and age distribution, even with optimal vaccine development in the next 5 years, it is not likely that > 50% of all cases will be prevented.

Invasive Haemophilus influenzae type b disease in children less than 5 years of age in Minnesota and in Dallas County, Texas, 1983-1984.

During 1983 and 1984, 733 cases of invasive Haemophilus influenzae type b disease in children less than 5 years of age were identified in Minnesota and in Dallas County, Texas. The overall incidence of disease was lower in Minnesota than in Dallas County. However, among urban residents, the rates of disease for whites were similar in the two areas. A higher rate of disease among whites in urban Minnesota compared with rural Minnesota resulted from an increased rate of cases for diagnoses other than meningitis. Local practices might have affected the rate of certain diagnoses, since ascertainment of Hib disease other than meningitis is more dependent on diagnostic practices than is diagnosis of meningitis. These data suggest that the incidence of invasive H. influenzae type b disease is influenced by the racial composition of the population, the rates of disease in specific subgroups, and possibly by local medical practices. Understanding the factors that contribute to the incidence of disease is necessary to interpret variations in different populations and changes over time.

The epidemiology of Haemophilus influenzae meningitis in children under five years of age in The Gambia, West Africa.

Haemophilus influenzae meningitis was studied over a 2-year period in children less than 5 years of age in a population-based, prospective study in The Gambia, West Africa. A total of 77 cases were recorded. The incidence was 60 cases/100,000 children less than 5 years of age and 297 cases/100,000 children less than 1 year of age. The peak prevalence was at the age of 5 months; 83% of the children were less than 1 year old and 45% were less than 6 months old. Only 55% of cases recovered completely. The distance to the nearest hospital was an important predisposing factor for a fatal outcome. Two cases were secondary. Many patients were anemic and underweight. The observations show that H. influenzae meningitis in The Gambia has an incidence as high as that in the USA, but that it has 10-fold more devastating outcome. If the infection is to be prevented by vaccination in The Gambia, immunization will have to be given very early in life.

Epidemiology of invasive Haemophilus influenzae type b infections in Bedouins and Jews in southern Israel.

We report the epidemiology of invasive Haemophilus influenzae type b disease requiring hospital intervention in Southern Israel, an area that contains two ethnic populations, Bedouins and Jews. The study is based on 107 blood or cerebrospinal fluid culture-positive cases during the years 1984 to 1988. The annual incidence rate among children younger than 5 years of age was 51/100,000 (48/100,000 for Jews and 58/100,000 for Bedouins). Thirty-nine percent of patients had meningitis, 32% had pneumonia and 31% had otitis media. Epiglottitis was present in only one case (less than 1%). The median age was 8 months. Twenty-six percent of the cases were 6 months old or younger, 75% were 1 year old or younger and 87% were 18 months old or younger. Ninety-five percent of all meningitis cases occurred during the first 18 months of life. A projected number of 2938 hospitalization days and 9.8 deaths/year for a population in which 100,000 births occur yearly was calculated. The major impact of invasive H. influenzae type b infections and the very young age involved justify initiation of H. influenzae vaccine studies in our region.

The epidemiology of invasive Haemophilus influenzae infections in children under five years of age in the Northern Territory: a three-year study.

A survey of all episodes of invasive Haemophilus influenzae infections that were diagnosed over a three-year period in children seen at the regional hospitals of the Northern Territory has found a significantly (P less than 0.001) higher incidence in children in Central Australia (the Alice Springs and Barkly regions, and the Anangu Pitjantjatjara Lands) than in the Top End (the Darwin, East Arnhem and Katherine regions), and a greater incidence in Aboriginal than in non-Aboriginal children. Identified risk factors for Aboriginal children were infancy (more than 70% of cases occurred before 12 months of age), sex (with a predominance in girls) and residence in Central Australia; the estimated annual incidence for Central Australian Aboriginal children was 991 cases per 100,000 children. There was a significant correlation (r = 0.62) between the total number of cases diagnosed each month in Central Australia and the mean monthly temperatures recorded in Alice Springs. Whereas virtually all cases of invasive H. influenzae infection in non-Aboriginal children were caused by type b strains, strains other than type b caused 15% of the cases in Aboriginal children. The possibilities for prevention by immunization are discussed.

[First results of bacteriologic study of strains of Haemophilus influenzae isolated from meningitis in the Abidjan University Hospital Center (Ivory Coast)]. / Premiers résultats d'une étude bactériologique de souches d'Haemophilus influenzae isolées de méningites au Centre Hospitalier Universitaire d'Abidjan (Côte d'Ivoire).

Biovars and serovars of 132 Haemophilus influenzae isolated from cerebro-spinal fluid (CSF) in Treichville hospital during a period of October 1986 to July 1988 were studied. Usual distribution was not found: biovar IV was first met (49.2%) followed by biovars I (28.8%), III (14.4%), II (6.1%) and V (1.5%). Strains belong to serovar b in 88% of cases.

Haemophilus influenzae meningitis in Manitoba and the Keewatin District, NWT: potential for mass vaccination.

A community-based surveillance study of all central nervous system infections was carried out in Manitoba and the Keewatin District, NWT, between Apr. 1, 1981, and Mar. 31, 1984. There were 201 cases of bacterial meningitis in Manitoba over the study period, 81 (40%) caused by Haemophilus influenzae; all but one isolate tested were type b (Hib). There were nine cases of H. influenzae meningitis in the Keewatin District. The overall annual incidence rate of H. influenzae meningitis in Manitoba was 2.5/100,000; for children under 5 years the rate was 32.1/100,000. For the Keewatin District the corresponding rates were 69.6/100,000 and 530/100,000. A total of 85% and 100% of the cases of H. influenzae meningitis occurred by 24 months of age in Manitoba and the Keewatin District respectively. The age at onset was earlier in native Indian children (22 cases) and Inuit children (9 cases) than in non-native children (59 cases) (p less than 0.005); thus, vaccine prevention of Hib meningitis will likely be more difficult in native Indian and Métis children. Without evaluating the increased potential of H. influenzae vaccines to prevent nonmeningitic forms of disease, we concluded that mass childhood vaccination with polyribosylribitolphosphate (PRP) vaccine is not warranted in Manitoba or the Keewatin District. Immunogenicity studies suggest that administration of conjugated Hib vaccines such as PRP-D in infancy may prevent approximately one-third to two-thirds of cases of H. influenzae meningitis; these vaccines warrant consideration for use in mass childhood vaccination programs.

Differences in the epidemiology of childhood community-acquired bacterial meningitis between two ethnic populations cohabiting in one geographic area.

A comparison of the epidemiology of community-acquired bacterial meningitis between Jewish and Bedouin populations cohabiting one geographical area is reported here. During the years 1981 to 1985, 100 children younger than 13 years old with community-acquired bacterial meningitis were hospitalized. Seventy-one patients were younger than 12 months. The principal bacteria isolated were Haemophilus influenzae 42%; Streptococcus pneumoniae 29% and Neisseria meningitidis 20%. The case fatality rate was 12%. The chance of acquiring meningitis during the first 5 years of life was twice as common among Bedouins than among Jews (328/100,000 vs. 173/100,000, respectively; P less than 0.0001). The most common cause of meningitis during the first year of life was S. pneumoniae among Bedouins and H. influenzae among Jews. Meningitis caused by H. influenzae and S. pneumoniae was usually associated with respiratory morbidity during fall and winter among Jews, but with diarrheal morbidity during summer and fall among Bedouins. Since the most prevalent type of morbidity among Jews results from respiratory infections and among Bedouins from diarrhea, our findings suggest that community-acquired bacterial meningitis is associated with the type of morbidity most prevalent in the community at any given season rather than with a specific type of infection.