Burden Of Haemophilus Influenzae Type Research Articles

A Systematic Review and Critical Evaluation of Invasive Haemophilus influenzae Type B Disease Burden Studies in Asia From the Last Decade

In Asia, questions regarding the burden of Haemophilus influenzae type b (Hib) disease have delayed decision-making on introduction of Hib vaccine. However, over the past decade many studies have been published regarding Hib disease burden in Asia. We conducted a systematic literature review of all reports of Hib disease burden in Asia between 1998 and 2009, and critically reviewed their methods and data quality. We identified 94 studies from 28 countries in Asia presenting data on Hib disease burden. Of the 94 studies reviewed, 49 (52%) used a case definition consistent with World Health Organization standards, and 47 (50%) described laboratory methodology used. Twenty-seven surveillance studies presented data on incidence of Hib disease, with 8 (30%) accounting for missed cases, 6 (15%) accounting for cases with missed diagnostic tests, and 2 (7%) that considered prior antibiotic use. Of the 21 studies that provided incidence data for Hib meningitis, 10 (48%) used active, prospective, population-based surveillance, and found unadjusted incidence rates of Hib meningitis ranging from a low of 0.98 per 100,000 child-years in children aged less than 5 years in China to a high of 28 per 100,000 child-years in children less than 5 years in Mongolia. Of 49 studies that reported the etiology of bacterial meningitis, 30 (60%) identified Hib as the most common cause. This review highlights the importance of using rigorous methodologies, including standardized surveillance methods and appropriate laboratory diagnostic tests, when conducting studies measuring the burden of invasive bacterial diseases including those caused by Hib. When poorly conducted, studies can underestimate disease burden and lead to inappropriate decisions about vaccine introduction.

Burden of Haemophilus influenzae type B disease in Pakistani children

Estimates of the burden of Haemophilus influenzae type b (Hib) in children in Pakistan are limited. A prospective surveillance was set up in 8 sentinel sites in Karachi and Hyderabad in January 2004. A total of 1481 children aged < 5 years underwent lumbar puncture for suspected acute bacterial meningitis. Specimens from 237 (16.0%) children met the criteria for probable bacterial meningitis, and Hib was detected in 45 of them (19.0%). The minimum detected incidence of Hib meningitis in the Hyderabad area was 7.6 per 100 000 in children < 5 years of age, and 38.1 per 100 000 children < 1 year. Hib vaccination is justified for inclusion in Pakistan's expanded programme of immunization.

Incidence of childhood Haemophilus influenzae type b meningitis in Sri Lanka

Objective To demonstrate the burden of Haemophilus influenzae type b (Hib) disease in Sri Lanka and provide information for decision-making in public health planning and vaccine introduction. Methods This was a prospective, population-based study carried out in 2004, to describe the epidemiology and calculate the incidence of meningitis caused by Hib in children <5 years of age in the district of Colombo, Sri Lanka. Hib was identified in cerebrospinal fluid (CSF) specimens by culture and antigen detection (latex agglutination test; LAT). Results The lumbar puncture rate in children <5 years of age was 1.9%. A causative bacterial organism was identified in 108 meningitis cases, and in 54 (50%) this was Hib. The LAT increased the Hib detection rate in CSF four-fold. In 2004, the annual incidence of Hib meningitis in Colombo was 20.1 cases per 100 000 children aged <5 years. Conclusions This study is the first from Sri Lanka reporting the Hib meningitis incidence rate pre-vaccine introduction. The reported incidence rate is one of the highest from the Asian region, but is likely an underestimation considering the difficulties in the laboratory identification of Hib.

FREQUENT HAEMOPHILUS INFLUENZAE TYPE B COLONIZATION IN RURAL THAILAND

In Asia, there is uncertainty regarding whether the burden of Haemophilus influenzae type b (Hib) disease is great enough to warrant vaccination. In this nasopharyngeal carriage study in rural Thailand, 7% of children younger than 5 years of age carried Hib, a prevalence similar to that found in countries with high rates of Hib disease before vaccine introduction.

Use of vaccine trials to estimate burden of disease.

Vaccine trials, the most informative way of determining the efficacy of a vaccine, can also provide valuable information about the burden of disease. The burden of Haemophilus influenzae type b (Hib) remains a major barrier to the use of Hib vaccines, especially in Asia. Recent studies in Indonesia and Bangladesh have used vaccine-trial designs, with known effective vaccines, to estimate the vaccine-preventable burden of Hib disease in those communities. New vaccines against pneumonia and diarrhoeal diseases are usually directed at only one of various causes of the syndrome. In the case of pneumonia, it is very difficult to determine the aetiology in most cases, so the vaccine trial offers a means of determining the burden of vaccine-preventable diseases. This is particularly important for pneumococcal vaccines as serotype replacement may reduce the effectiveness of the vaccines in the field. This approach would underestimate disease burden if vaccines were found to have an impact on syndromes other than those against which they are directed, and might lead to errors in estimation if there were erroneous assumptions about the efficacy of the vaccine against the condition under investigation.

The introduction of routine Haemophilus influenzae type b conjugate vaccine in Chile: a framework for evaluating new vaccines in newly industrializing countries.

To determine the burden of Haemophilus influenzae type b (Hib) disease, the safety and immunogenicity of Hib conjugate vaccine, the practicality of combining Hib conjugate and diphtheria-tetanus-pertussis vaccines and the effectiveness of routine vaccination. A series of studies were carried out involving infants and children in Santiago, Chile. The study designs included retrospective surveillance, cost-benefit analysis, randomized placebo-controlled trials of safety and immunogenicity and a Phase IV postlicensure evaluation of vaccine effectiveness. The studies included in this stepwise process showed that Hib invasive disease was a significant public health problem with a substantial economic burden; that combining Hib conjugate and diphtheria-tetanus-pertussis vaccines was practical, safe and elicited a strong immunologic response; and that the combined formulation afforded a high level of protection against invasive Hib disease (90% effectiveness). In July, 1996, Chile became only the third newly industrializing country to introduce routine Hib conjugate vaccination. New vaccines, such as Hib conjugates, will be more expensive than existing ones. The stepwise process used in Chile may serve as an example for the evaluation of new vaccines in nonindustrialized countries.

The Gambian Haemophilus influenzae type b vaccine trial: what does it tell us about the burden of Haemophilus influenzae type b disease?

The true burden of disease caused by Haemophilus influenzae type b (Hib) remains a mystery in many parts of the developing world. The most frequent manifestations of Hib disease are pneumonia and meningitis. In developing countries where it has been studied, Hib has proved to be a major cause of infant meningitis, generally occurring with greater frequency, in younger infants and with a worse outcome than in industrialized countries in the prevaccine era. The burden of Hib pneumonia is more difficult to define. Studies from developing countries of pneumonia etiology suggested that Hib was responsible for 5 to 10 of episodes of severe pneumonia. A Gambian study found Hib to be responsible for 7% of cases. However, a recently published trial of a Hib conjugate vaccine in Gambian infants showed that the vaccine prevented 21% of episodes of severe pneumonia in vaccine recipients, suggesting that this is the true contribution of Hib to the burden of severe pneumonia. The same trial demonstrated a mild herd effect, so this figure may be an underestimate. The biases that lead to the underestimation of the contribution of Hib to the pneumonia burden also apply to estimates of the proportion of severe pneumonia caused by Streptococcus pneumoniae. Vaccine trials may reveal the true burden of that pathogen also.

The burden of Haemophilus influenzae type b disease in Australia ana an economic appraisal of the vaccine PRP‐OMP

To estimate the incidence and sequelae of Haemophilus influenzae type b disease (Hib) in the Australian population, and to evaluate the costs and outcomes of a vaccination program using the vaccine PRP-OMP at two, four and 12 months. The evaluation was based on a decision analytic model developed by Merck Sharp and Dohme (Australia) Pty Ltd, to predict the number of children who would contract Hib, and suffer mild or severe sequelae or die as a result. The state of health of a cohort of children was modelled each month over a five-year period. A survey of medical records and interviews with parents of children who contracted meningitis in Western Australia from 1984-1990 was undertaken to provide data on the extent and costs of sequelae. The incidence of Hib among non-Aboriginal Australians under five years of age was estimated as 53 per 100,000, and 460 per 100,000 among Aborigines. In a single year at least 630 children may contract Hib, up to 19 may die, and a further 46 may have neurological damage, this being severe in up to 18 children. The number of deaths could be reduced by 17 per year and a further 25 cases of severe and 16 cases of mild disability could be averted. At a price of $20 per dose, and a 5% discount rate, the expected cost per year of life extended by a vaccination program is $3148. When adjusted for the increased number of years without neurological impairment, the incremental cost per quality adjusted life year (QALY) is $1965. Compared with a single vaccine at 18 months, the incremental cost per additional QALY gained is $5047. A separate analysis of the Aboriginal population showed that the proposed vaccination program would be of significant benefit, leading to a saving of resources.