Nasopharyngeal colonization with Haemophilus influenzae type b among infants and children in Japan

Epidemiology and burden of Haemophilus influenzae disease in Thai children before implementation of the routine immunisation programme: A National Health Data Analysis

OBJECTIVES

To conduct the first pre-Haemophilus influenzae (Hi) type b (Hib) immunisation programme-based epidemiological study using national health data.

METHODS

We analysed National Health Security Office data, which cover 72% of the Thai population. The study population included children aged <18 years admitted for Hi disease from 2015 to 2019. Hi disease diagnosis and death were based on the International Statistical Classification of Diseases and Related Health Problems (10th revision) hospital discharge summary codes. We estimated the hospital cost per admission using diagnosis-related grouping with a global budget.

RESULTS

A total of 1125 children aged <18 years were admitted for Hi disease. During the 5-year-study, the annual incidence of Hi disease varied from 1.5 to 1.9 per 100,000 children, with an overall case fatality rate (CFR) of 2%. Pneumonia was the most common clinical form, followed by meningitis and sepsis. The incidence, clinical forms and severity of Hi disease were age specific. Infant CFR was higher than that of other age groups. The incidence of Hi disease in children aged <5 years was 4.9 per 100,000 (CFR = 2.0%). Sepsis was the primary cause of infant death, whereas pneumonia was the cause of death in children aged >5 years. The hospital cost ranged from 25,000 to 30,000 THB per admission.

CONCLUSIONS

This analysis provided epidemiological data of Hi in Thai children before the Hib routine immunisation programme. The incidence of Hi disease was lower than that previously speculated. Our results could facilitate an assessment of the impact of Hib immunisation programme in Thailand.

A model for the incremental burden of invasive Haemophilus influenzae type b due to a decline of childhood vaccination during the COVID-19 outbreak: A dynamic transmission model in Japan

BACKGROUND

The current coronavirus disease 2019 (COVID-19) outbreak has caused a persistent decline in childhood vaccination coverage, including Haemophilus influenzae type b (Hib) vaccine, in some countries. Our objective was to evaluate the impact of decreased Hib vaccination due to COVID-19 on invasive Hib disease burden in Japan.

METHODS

Using a deterministic dynamic transmission model (susceptible-carriage-infection-recovery model), the incidence rates of invasive Hib disease in under 5 year olds in rapid vaccination recovery and persistent vaccination declined scenarios were compared for the next 10 years after 2020. The national Hib vaccination rate after the impact of COVID-19 reduced to 87% and 73% in 2020 from approximately 97% each in 2013-2019 for primary and booster doses.

RESULTS

While the persistent decline scenarios revealed an increase in invasive Hib disease incidence to 0.50/100,000 children under 5 years old, the incidence of the rapid recovery scenario slightly increased with a consistent decline of incidence after 2021. The shorter the duration of the decline in vaccination rate was, the smaller the incremental disease burden observed in the model. Compared to the rapid recovery scenario, the permanent decline scenario showed a 296.87 cumulative incremental quality-adjusted life years (QALY) loss for the next 10 years.

CONCLUSIONS

The persistent decline of Hib vaccination rate due to COVID-19 causes an incremental disease burden irrespective of the possible decline of Hib transmission rate by COVID-19 mitigation measures. A rapid recovery of vaccination coverage rate can prevent this possible incremental disease burden.

Changes in nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis among healthy children attending a day-care centre before and after official financial support for the 7-valent pneumococcal conjugate vaccine and H. influenzae type b vaccine in Japan

The 7-valent pneumococcal conjugate vaccine (PCV7) and Haemophilus influenzae type b (Hib) vaccine reduce nasopharyngeal carriage of vaccine-type bacteria, which may in turn influence the presence of other nasopharyngeal bacterial pathogens. To investigate this possibility, nasopharyngeal carriage of potential pathogens was examined before and after official financial support was provided to offer the PCV7 and Hib vaccines in healthy children attending a day care centre in Japan during 2011-2012. Despite a virtual disappearance of PCV7 serotypes over time, the overall pneumococcal carriage rate remained unchanged. Although others have reported an increase in PCV13 serotypes following PCV7 vaccination, only non-PCV13 serotypes were observed to have increased in this study. The majority of H. influenzae isolates were non-typeable and Hib was not found. Our data identified an unexpected pattern of pneumococcal serotype replacement following PCV7. Continuous monitoring of pneumococcal carriage is important for decisions regarding the future of national vaccination policy in Japan.

The continuing role of Haemophilus influenzae type b carriage surveillance as a mechanism for early detection of invasive disease activity

Prior to the introduction of Haemophilus influenzae type b (Hib) conjugate vaccines, Hib was the leading cause of bacterial meningitis in children under five years of age worldwide. In countries that have adopted Hib vaccination schedules, invasive disease has reduced markedly. Oro-naso pharyngeal carriage is recognized as the most significant source of infection. Hib carriage is significantly associated with poverty, such as overcrowding, poor ventilation in houses, lack of running water, and high smoking rates. Additionally, many Indigenous minority groups report high rates of Hib carriage. A resurgence of Hib disease among Alaskan children in the 1990s, lead to a change in approach to eliminate Hib disease and carriage in high-risk populations. This new approach identifies strategies for eliminating Hib disease focusing on the reservoirs of colonization within families and communities. Monitoring Hib carriage continues to offer an early warning system, whereby intervention could prevent invasive disease resurgence.

Genotyping of Haemophilus influenzae type b in pre-vaccination era

Identification of Haemophilus influenzae type b (Hib) in asymptomatic carriers is critical to control the spread of disease. This study was conducted between January 2008 and August 2011 as part of a birth cohort study in Sado Island, Japan, to elucidate the prevalence of Hib and its clones in a specific region. Nasopharyngeal cultures were obtained from 349 subjects at 4-, 7-, 10-, 18-, and 36-month health checkups and analyzed for H. influenzae. The Hib and nontypeable H. influenzae detection rates ranged from 0 to 1.5% (12 isolates) and from 7.9 to 32.9%, respectively. Twelve pediatric patients diagnosed with invasive or non-invasive Hib infections during the study period were also enrolled. The Hib isolates were analyzed for carriage of the beta-lactamase gene and ftsI mutations, and multilocus sequence type (MLST, ST type). Of the 24 Hib isolates, 18 (75%) were ST54, 5 (21%) were ST190, and 1 isolate (4%) was ST95. All of the ST190 isolates were genetically beta-lactamase-negative ampicillin-susceptible isolates, while all but one of the ST54 isolates were genetically beta-lactamase-positive amoxicillin/clavulanic acid-resistant isolates. The geographic distribution of Hib isolates in the study period was scattered. There were 2 day-care cases and 1 family case of Hib infection. The ST54 and ST190 strains circulated in Sado Island and were detected in both asymptomatic carriers and patients. We note that surveillance of healthy subjects to identify Hib carriers is important to understand the transmission of Hib.

The impact of vaccines on pneumonia: key lessons from Haemophilus influenzae type b conjugate vaccines

This article explores key lessons learned from vaccination with Haemophilus influenzae type b (Hib) conjugate vaccine and how these lessons may provide insight into the impact of emergent pneumococcal vaccines against pneumonia. The worldwide value of Hib vaccination for reducing Hib disease burden and carriage is reviewed. Using comparisons of data for pneumococcus versus Hib, the article concludes that epidemiological and biological differences between these pathogens will complicate efforts to use results from the Hib vaccine experience to predict outcomes following pneumococcal conjugate vaccine introduction.

Rapid identification of nontypeable and serotype b Haemophilus influenzae from nasopharyngeal secretions by the multiplex PCR

OBJECTIVE

Heamophilus influenzae (H. influenzae) is an important pathogen responsible for both invasive and non-invasive infectious diseases. While encapsulated type b strain recognized as a major cause of severe invasive diseases, nontypeable strains are the major causes of non-invasive infectious diseases. Detection of this pathogen from nasopharyngeal secretions (NPS) is important.

METHODS

We developed a multiplex polymerase chain reaction (PCR) for rapid identification of nontypeable and serotype b H. influenzae from nasopharyngeal secretions.

RESULTS

A total 25 nasopharyngeal secretions were evaluated in this study. The multiplex PCR provided rapid and unequivocal results for determining either nontypeable or encapsulated typeable especially type b strains including a determination of beta-lactamase productions.

CONCLUSION

The multiplex PCR based serotyping provided more reliable results than slide agglutination test (SAT) and is a valuable and expeditious method for identification of H. influenzae with determining capsular serotypes.

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.

Pharyngeal colonization with Haemophilus influenzae type b among healthy Turkish infants and children

BACKGROUND

An absence of Haemophilus influenzae type b (Hib) disease surveillance and epidemiological data on the pharyngeal carriage of Turkish children causes delay in the introduction of conjugated Hib vaccination into proposed national vaccination programs.

METHODS

Oropharyngeal cultures were obtained from 1404 healthy infants and children. Six healthy child clinic (HCC), 11 day-care centers (DCC) and seven elementary schools (ES) were randomly selected in seven different counties at the Anatolian side of Istanbul between January and April 2000.

RESULTS

Haemophilus influenzae was isolated from 315 (22.8%) of all participants and 98 (31%) isolates were serotype b. The carriage rate for Hib was higher in children at DCC (43 out of 448, 9.6%) and ES (46 out of 504, 9.1%) compared to infants 0-24 months of age (nine out of 430, 2.1%) presented to HCC. All Hib isolates were susceptible to azithromycin, chloramphenicol and cefotaxime. Beta-lactamase production was detected in only one isolate. Trimethoprim-sulfamethoxazole resistance was found in 8.5% of Hib isolates. Multivariate analysis showed that DCC and ES attendance were independent predictors of Hib carriage.

CONCLUSION

A significant proportion of healthy Turkish children was shown to be colonized with Hib. The burden of invasive Hib infections should be determined in order to evaluate the Hib conjugated vaccine as a part of a routine immunization program in Turkey.

Prevalence of Haemophilus influenzae pharyngeal carriers in the school population of Catalonia. Working Group on invasive disease caused by Haemophilus influenzae

The objective of this study was to determine the prevalence of healthy Haemophilus influenzae (Hi) pharyngeal carriers in a representative sample of the Catalonian school population, as well as the factors associated. A two-stage cluster sampling was carried out. Parents were given a questionnaire to collect information on sociodemographic and epidemiological variables. A pharyngeal swab was performed on children when informed consent was given by parents, and was cultured on chocolate agar with 260 microg/ml bacitracin. Of the 1212 children studied, 316 (26%) H. influenzae carriers were detected: 5 (0.4%) serotype b, 1 (0.08%) serotype c, 6 (0.5%) serotype e, 5 (0.4%) serotype f, and 299 (24.7%) non-typable. Age, gender and geographical location were the only variables associated with H. influenzae carrier status. The prevalence of non-typable H. influenzae carriers was similar to that of studies carried out in other countries, while that of serotype b carriers was similar to the remainder of H. influenzae capsulates, and lower than that described in previous studies. These data are in accordance with the low incidence of the disease observed in our context, although the possibility that the vaccine coverage may have affected the results of this study cannot be dismissed.

Incidence of Haemophilus influenzae in the throats of healthy infants with different feeding methods

BACKGROUND

Haemophilus influenzae is the major cause of otitis media and lower respiratory tract infection in childhood. In the presence of human milk, which contains numerous host defense factors, Haemophilus influenzae may be inhibited in attaching to and colonizing pharyngeal cells. We investigated the incidence of H. influenzae in the throats of 162 healthy infants with different feeding methods: 70 breast-fed, 49 mixed-fed and 43 formula-fed infants.

METHODS AND RESULTS

Haemophilus influenzae was identified using standard microbiological procedures and the API NH system. The incidence of H. influenzae in breast-fed infants, mixed-fed infants and formula-fed infants was 0, 0 and 7.0% respectively.

CONCLUSION

The results suggest that the colonization of H. influenzae in the throat was inhibited by the presence of breast milk.

A population-based survey of Haemophilus influenzae type b nasopharyngeal carriage prevalence in Lombok Island, Indonesia

BACKGROUND

The Haemophilus influenzae type b (Hib) nasopharyngeal carriage prevalence and invasive disease incidence rates are unknown in Indonesia; consequently Hib vaccine is not included in the routine vaccine schedule.

METHODS

To determine carriage prevalence we conducted a population-based, island-wide prospective study of a systematic sample of 484 children 0 to 2 years of age in Lombok, Indonesia. We conducted a risk factor questionnaire and determined serotypes and antibiotic sensitivity patterns.

RESULTS

We identified 155 H. influenzae isolates, of which 22 were type b and 12 were encapsulated but not type b. The age- and population-weighted Hib carriage prevalence, adjusted for the sampling design, was 4.6% (95% confidence interval, 3.7 to 5.5%). Children younger than 6 months of age had a carriage prevalence less than one-half that of older children, and carriage varied within the four administrative regions of the island; otherwise no risk factors for Hib carriage were identified. All Hib specimens were sensitive to ampicillin and 20 (91%) were sensitive to chloramphenicol.

CONCLUSIONS

The Hib carriage prevalence in Lombok is similar to that found in developed countries before vaccine introduction. This suggests that further studies should proceed to determine whether Lombok has invasive disease rates as high as those that justified vaccine introduction in developed countries.