The first reported case of possible Haemophilus influenzae type b vaccine failure from Kuwait and literature-review

Haemophilus influenzae Type b Vaccine Failure in Portugal: A Nationwide Multicenter Pediatric Survey

BACKGROUND

Despite the high effectiveness of the Haemophilus influenzae type b (Hib) vaccine in preventing invasive disease (ID) in children, Hib vaccine failures (VFs) cases may still occur. This study aimed to characterize the Hib-VF cases in Portugal in a 12-year period and trying to identify the possible associated risk factors.

METHODS

Prospective descriptive nationwide surveillance study. Bacteriologic and molecular studies were performed at the same Reference Laboratory. Clinical data were collected by the referring pediatrician.

RESULTS

Hib was identified in 41 children with ID and 26 (63%) were considered VF. Nineteen (73%) cases occurred in children less than 5 years old; 12 (46%) occurred before the Hib vaccine booster dose at 18 months of age. Comparing the first and the last 6-year periods of the study, the incidence rate of Hib, VF and total H. influenzae (Hi) ID significantly raised ( P < 0.05). VF cases corresponded, respectively, to 13.5% (7/52) and 22% (19/88) of total Hi-ID cases ( P = 0.232). Two children died due to epiglottitis and 1 acquired sensorineural hearing loss. Only 1 child had an inborn error of immunity. The immunologic workup performed in 9 children revealed no significant abnormalities. All 25 Hib-VF strains analyzed belonged to the same clonal complex 6.

CONCLUSIONS

In Portugal, more than 95% of children are vaccinated against Hib, but severe Hib-ID cases still occur. No predisposing factors were clearly identified to justify the increased number of VF in recent years. Along with continued Hi-ID surveillance, Hib colonization and serologic studies should be implemented.

Respiratory Carriage of Haemophilus influenzae Associated with Hib Vaccine in Jordanian Children

Objective Haemophilus influenzae type b (Hib) is the most virulent serotype that colonizes the upper respiratory tract of children. After introducing Hib conjugate vaccine, Hib has become almost entirely replaced by nontypeable H. influenzae (NTHi) strains. This study investigated the incidence of NTHi, which may cause serious sporadic body infections.

Methods A total of 300 nasal and throat swab samples were obtained from children aged 6 to 60 months, who visited outpatient pediatric clinics of Jordan University Hospital and Al-Bashir Hospital, Amman, Jordan. Colonies resembling H. influenzae were tested by conventional laboratory tests including Gram staining and antibiotic susceptibility. The 16S rRNA and bexA (capsulation gene) were amplified from the extracted DNA. Swabs (n = 100) were delivered to the laboratory in transport media. After initial culture, DNA was extracted directly and tested by conventional polymerase chain reaction (PCR) employing actin beta primers for assessing the housekeeping gene, followed by quantitative PCR (qPCR) against Hib-specific primers.

Results A total of 31/300 (10.33%) of H. influenzae isolates were recovered by culture and confirmed by PCR for 16S rRNA; 96.77% (30/31) were NTHi, and only one isolate was Hib. This isolate was confirmed by detection region II of the cap locus of Hib gene by qualitative TaqMan real-time qPCR. Antibiotic resistance among NTHi to ampicillin and erythromycin was 50.0 and 20.0%, respectively.

Conclusion The conjugated Hib vaccine almost eliminated the occurrence of Hib in the upper respiratory tract of the Jordanian children, while NTHi colonization was found in 10% of them.

Analysis of Haemophilus species in patients with respiratory tract infections in Yaoundé, Cameroon

OBJECTIVES

To identifyHaemophilus species and characterize antimicrobial susceptibility of isolates from patients with respiratory tract infections (RTIs) in Cameroon.

METHODS

Isolates (n = 95) were from patients with RTIs obtained from two Hospitals in Yaoundé, Cameroon. Isolates were identified by biochemical assay, PCR-based method, MALDI-TOF and whole genome sequencing. Antibiotic minimum inhibitory concentrations were determined by E-test.

RESULTS

H. influenzae was the most prevalent species varying from 76.8% to 84.2% according to different methods. The isolates were mainly nontypable (n = 70, 96%). Three isolates of H. influenzae were capsulated (b, e and f). The isolates were genetically diverse and 40 unique sequence types were identified including 11 new ones. Resistance to ampicillin was observed among 55.3% (52/94) and 9% (14/52) produced TEM-1 β-lactamase. PBP3 mutations occurred in 57.7% of ampicillin resistant isolates (30/52). Eleven isolates were chloramphenicol resistant with 80% producing chloramphenicol acetyltransferase (8/10). Four Haemophilus isolates were rifampicin resistant with two mutations in rpoB gene. Five isolates were ciprofloxacin resistant and harbored mutations in the quinolone resistance determining regions of gyrA and parC genes.

CONCLUSION

H. influenzae isolates are highly diverse and show high levels of antibiotic resistance. H. influenzae serotype b is still circulating in the post-vaccination era.

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.

Immune responses to vaccine-preventable diseases among toddlers and preschool children after primary immunization and first booster in Northwestern Algiers, Algeria

OBJECTIVES

To determine immune responses to selected vaccine-preventable communicable diseases: pertussis, diphtheria and Haemophilus influenzae type b (Hib) in Algerian toddlers and preschool children after primary vaccination and first booster, recruited from three local healthcare facilities in Northwestern Algiers.

METHODS

The information of demographic characteristics and vaccination status were collected for each subject by questionnaire. Specific antibody levels and Hib antibody avidity were determined using commercial ELISA kits.

RESULTS

A total of eighty-one subjects aged between 19 and 55 months were studied. Almost all subjects were fully protected against diphtheria (76/81; 93.83%; 95% CI: 86.35-97.33) and invasive Hib disease (29/30; 96.67%; 95% CI: 83.33-99.41), while only 20/78 (25.64%; 95% CI: 17.26-36.31) had anti-PT (pertussis toxin) antibody levels above 25 IU/ml. A significant decrease of anti-PT antibody levels was observed until the age of 36 months (p = 0.02). GMTs (geometric mean titers) of anti-PT antibodies were low, but remain significantly higher in children ≤36 months of age (p = 0.02). Both GMT and rates of ≥0.15 μg/ml, ≥1 μg/ml, and ≥5 μg/ml titers were significantly higher in Hib-vaccinated subjects (p < 0.01). Relative Hib-avidity index (≥50%) and GMAI (geometric mean avidity index) were high in both Hib-vaccinated and -unvaccinated groups.

CONCLUSIONS

As shown in the present study, young children were fully protected against diphtheria and Hib, but showed low immunity to pertussis. Further sero-epidemiological studies including a large number of subjects with a wider range of age are needed to explore the immunity level in older children, adolescents and adults.

Vaccine-Preventable Diseases Requiring Hospitalization

BACKGROUND

Plain children often have lower immunization rates than non-Plain children. Penn State Health Children's Hospital is a tertiary medical center with large nearby Plain (Amish and Mennonite) communities. We sought to describe the characteristics of children hospitalized with vaccine-preventable diseases (VPDs). We hypothesized that Amish children would have a higher risk of VPDs than non-Amish children.

METHODS

International Classification of Diseases, Ninth Revision codes were used to identify patients <18 years diagnosed with a VPD from January 1, 2005, to December 31, 2015, at Penn State Children's Hospital. Demographic information, immunization status, and outcomes were obtained from medical records. By using the number of children in our primary service area, we calculated the risk of VPD requiring hospitalization for Amish and non-Amish children. We assessed the relationship between Plain affiliation and vaccination status by using the Pearson correlation coefficient.

RESULTS

There were 215 children with 221 VPDs. Most occurred in non-Plain children: 179 of 221 (81%). Except for pneumococcal infections, VPD occurred mostly in unvaccinated or immunocompromised children, regardless of Plain affiliation. There were 15 Haemophilus influenzae type b and 5 tetanus infections that occurred in children with an unvaccinated or unknown vaccination status. The risk of a VPD requiring hospitalization was greater for Amish than for non-Plain children (risk ratio: 2.67 [95% confidence interval: 1.87-3.82]). There was a strong correlation between Plain affiliation and lack of vaccination (r = -0.63, P < .01).

CONCLUSIONS

Amish children had an increased risk of a VPD requiring hospitalization than non-Plain children. With the exception of those with pneumococcal disease, most vaccinated children hospitalized with a VPD were immunocompromised.