Haemophilus influenzae type b (Hib) seroprevalence in France: impact of vaccination schedules

Preferences of healthcare providers in Switzerland for attributes of pediatric hexavalent vaccines: a discrete-choice experiment

OBJECTIVE

To understand the preferences of healthcare providers (HCPs) in Switzerland for pediatric hexavalent vaccine attributes.

METHODS

A discrete-choice experiment included a series of choices between 2 hypothetical pediatric hexavalent vaccines with varying attributes: device type (including preparation time and risk of dosage errors), proportion of infants seroprotected against Haemophilus influenzae type b (Hib) at 11-12 months (pre-booster), packaging size, years on the market, and the thermostability at room temperature. Odds ratios (ORs) and conditional relative attribute importance (CRAI) were calculated using random-parameters logit.

RESULTS

HCPs (150 pediatricians and 40 nursing staff) in Switzerland were unlikely to choose a vaccine conferring 50% (OR 0.00; 95% CI 0.00-0.00) or 70% (OR 0.01; 95% CI 0.00-0.01) of infants with Hib seroprotection at 11-12 months (pre-booster) compared with a vaccine conferring 90% seroprotection. The odds of choosing a vaccine available on the market for more than 3 years were nearly 5 times the odds of choosing a vaccine available on the market for less than 1 year (OR 4.76; 95% CI 1.87-7.65). The odds of choosing a vaccine in a prefilled syringe were nearly 3 times the odds of choosing a reconstituted vaccine (OR 2.77; 95% CI 1.39-4.15), and the odds of choosing a vaccine with a smaller package size were nearly 2 times the odds of choosing a vaccine with larger package size (OR 1.89; 95% CI 1.23-2.55). HCPs were equally likely to choose vaccines that can stay at room temperature for 6 versus 3 days (OR 1.07; 95% CI 0.73-1.42). According to CRAI, the most important attribute was Hib seroprotection, followed by years on the market, device type, and packaging size.

CONCLUSION

Hib seroprotection at 11-12 months was the most important hexavalent vaccine attribute to HCPs in this study.

Vaccine-preventable Pediatric Acute Bacterial Meningitis in France: A Time Series Analysis of a 19-Year Prospective National Surveillance Network

BACKGROUND

In France, vaccination has been implemented against Hi serotype b (Hib), pneumococcus with pneumococcal conjugate vaccines (PCV), and Neisseria meningitidis serogroup C (MenC). These interventions with different coverage and uptake have disrupted the epidemiology of vaccine-preventable acute bacterial meningitis (ABM).

METHODS

We analyzed data from a French prospective surveillance network of ABM in children ≤15 years old enrolled by 259 pediatric wards (estimated national coverage: 61%). From 2001 to 2020, the effect of vaccine implementation was estimated with segmented linear regression.

RESULTS

We analyzed 7,186 cases, mainly due to meningococcus (35.0%), pneumococcus (29.8%), and Hi (3.7%). MenC ABM incidence decreased (-0.12%/month, 95% CI: -0.17 to -0.07, P < 0.001) with no change for the overall meningococcal ABM when comparing the pre-MenC vaccination and the post-MenC vaccination trends. Despite a decreasing MenB ABM incidence without a vaccination program (-0.43%/month, 95% CI: -0.53 to -0.34, P < 0.001), 68.3% of meningococcal ABM involved MenB. No change in pneumococcal ABM incidence was observed after the PCV7 recommendation. By contrast, this incidence significantly decreased after the switch to PCV13 (-0.9%/month, 95% CI: -1.6 to -0.2%, P = 0.01). After May 2014, a rebound occurred (0.5%/month, 95% CI: 0.3-0.8%, P < 0.001), with 89.5% of non-PCV13 vaccine serotypes. Hib ABM incidence increased after June 2017.

CONCLUSIONS

PCV7 and MenC vaccine introduction in France, with slow vaccine uptake and low coverage, had no to little impact as compared to the switch from PCV7 to PCV13, which occurred when coverage was optimal. Our data suggest that MenB and next-generation PCVs could prevent a large part of the ABM incidence in France.

Population immunity to pneumococcal serotypes in Kilifi, Kenya, before and 6 years after the introduction of PCV10 with a catch-up campaign: an observational study of cross-sectional serosurveys

BACKGROUND

In Kilifi (Kenya), a pneumococcal conjugate vaccine (PCV10) was introduced in 2011 in infants (aged <1 year, 3 + 0 schedule) with a catch-up campaign in children aged 1-4 years. We aimed to measure the effect of PCV10 on population immunity.

METHODS

In this observational study, repeated cross-sectional serosurveys were conducted in independent random samples of 500 children younger than 15 years every 2 years between 2009 and 2017. During these surveys, blood samples were collected by venesection. Concentrations of anti-capsular IgGs against vaccine serotypes (VTs) 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F, and 23F, and against serotypes 6A and 19A, were assayed by ELISA. We plotted the geometric mean concentrations (GMCs) by birth year to visualise age-specific antibody profiles. In infants, IgG concentrations of 0·35 μg/mL or higher were considered protective.

FINDINGS

Of 3673 volunteers approached, 2152 submitted samples for analysis across the five surveys. Vaccine introduction resulted in an increase in the proportion of young children with protective IgG concentrations, compared with before vaccine introduction (from 0-33% of infants with VT-specific levels over the correlate of protection in 2009, to 60-94% of infants in 2011). However, among those vaccinated in infancy, GMCs of all ten VTs had waned rapidly by the age of 1, but rose again later in childhood. GMCs among children aged 10-14 years were consistently high over time (eg, the range of GMCs across survey rounds were between 0·45 μg/mL and 1·00 μg/mL for VT 23F and between 2·00 μg/mL and 3·11 μg/mL for VT 19F).

INTERPRETATION

PCV10 in a 3 + 0 schedule elicited protective IgG levels during infancy, when disease risk is high. The high antibody levels in children aged 10-14 years might indicate continued exposure to vaccine serotypes due to residual carriage or to memory responses to cross-reactive antigens. Despite rapid waning of IgG after vaccination, disease incidence among young children in this setting remains low, suggesting that lower thresholds of antibody, or other markers of immunity (eg, memory B cells), may be needed to assess population protection among children who have aged past infancy.

FUNDING

Gavi, the Vaccine Alliance; Wellcome Trust.

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.

Scale-Up of Capsular Polysaccharide Production Process by Haemophilus influenzae Type b Using kLa Criterion

Polyribosyl-ribitol-phosphate (PRP) from Haemophilus influenzae type b (Hib) is an active immunizing molecule used in the production of the vaccine against H. influenzae, and industrial production could contribute to satisfying a world demand especially in developing countries. In this sense, the aim of this study was to establish a scale-up process using the constant oxygen mass transfer coefficient (k_La) such as the criterion for production of PRP in three different sizes of bioreactor systems. Three different k_La values (24, 52 and 80 h⁻¹) were evaluated in which the biological influence in a 1.5 L bioreactor and 52 h⁻¹ was selected to scale-up the production process until a 75 L pilot-scale bioreactor was achieved. Finally, the fed-batch phase was started under a dissolved oxygen concentration (pO₂) at 30% of the saturation in the 75 L bioreactor to avoid oxygen limitation; the performance of production presented high efficiency (9.0 g/L DCW-dry cell weight and 1.4 g/L PRP) in comparison with previous scale-up studies. The yields, productivity and kinetic behavior were similar in the three-size bioreactor systems in the batch mode indicating that k_La is possible to use for PRP production at large scales. This process operated under two stages and successfully produced DCW and PRP in the pilot scale and could be beneficial for future bioprocess operations that may lead to higher production and less operative cost.

Cellular and Humoral Immune Response to a Third Dose of BNT162b2 COVID-19 Vaccine – A Prospective Observational Study

Background

Since the introduction of various vaccines against SARS-CoV-2 at the end of 2020, infection rates have continued to climb worldwide. This led to the establishment of a third dose vaccination in several countries, known as a booster. To date, there has been little real-world data about the immunological effect of this strategy.

Methods

We compared the humoral- and cellular immune response before and after the third dose of BioNTech/Pfizer vaccine BNT162b2, following different prime-boost regimen in a prospective observational study. Humoral immunity was assessed by determining anti-SARS-CoV-2 binding antibodies using a standardized quantitative assay. In addition, neutralizing antibodies were measured using a commercial surrogate ELISA-assay. Interferon-gamma release was measured after stimulating blood-cells with SARS-CoV-2 specific peptides using a commercial assay to evaluate the cellular immune response.

Results

We included 243 health-care workers who provided blood samples and questionnaires pre- and post- third vaccination. The median antibody level increased significantly after the third vaccination dose to 2663.1 BAU/ml vs. 101.4 BAU/ml (p &lt; 0.001) before administration of the booster dose. This was also detected for neutralizing antibodies with a binding inhibition of 99.68% ± 0.36% vs. 69.06% ± 19.88% after the second dose (p &lt; 0.001). 96.3% of the participants showed a detectable T-cell-response after the booster dose with a mean interferon-gamma level of 2207.07 mIU/ml ± 1905 mIU/ml.

Conclusion

This study detected a BMI-dependent antibody increase after the third dose of BNT162b2 following different vaccination protocols. All participants showed a significant increase in their immune response. This, in combination with the low rate of post-vaccination-symptoms underlines the potential beneficial effect of a BNT162b2-booster dose.

Changes in Invasive Neisseria meningitidis and Haemophilus influenzae Infections in France during the COVID-19 Pandemic

BackgroundSince the appearance of COVID-19 in January 2020, invasive bacterial infections have decreased significantly worldwide. However, alterations in age and sex distributions, clinical forms, phenotypes, and genotypes of isolates have not been analyzed. Our goal is to present and discuss these data considering the current COVID-19 pandemic situation. Methods: The data of the national reference center for meningococci and Haemophilus influenzae in France were mined to examine the above aspects of invasive bacterial infection before (2018−2019) and after (2020−2021) the COVID-19 pandemic. Detailed epidemiological, clinical, and microbiological data were collected, and whole genome sequencing was carried out on meningococcal isolates (n = 1466). Results: In addition to the overall decline in the number of cases, various changes in age, sex, and phenotypes of isolates were also noted. As for N. meningitidis, more cases were observed in adults, as well as more invasive pneumopathies. Furthermore, fewer hyperinvasive meningococcal genotypes have circulated since COVID-19 emerged. The situation has been different for H. influenzae, as the number of invasive cases among adults decreased due to a reduction in non-typeable isolates. In contrast, cases due to serotypeable isolates, particularly serotypes a and b, increased in children <5 years-old. Conclusions: It is possible that measures implemented to stop COVID-19 may have reduced the circulation of N. meningitidis and H. influenzae isolates, but to a variable extent. This may be due to differences in circulation between these two species according to age groups. Vaccination schedules against these two species may have also influenced the evolution of these invasive bacterial infections since the emergence of the COVID-19 pandemic.

From Genetics to Epigenetics: Top 4 Aspects for Improved SARS-CoV-2 Vaccine Designs as Paradigmatic Examples

This literature review described the genetic and biochemical factors that may have been overlooked in the formulation of vaccines and that most likely underlie possible issues with mass vaccination.

Increase in invasive disease caused by Haemophilus influenzae b, the Netherlands, 2020 to 2021

The incidence of most respiratory-transmitted diseases decreased during the COVID-19 pandemic as a result of containment measures. In contrast, in the Netherlands we noted an increase in invasive disease caused by Haemophilus influenzae b (Hib) (from < 0.3/100,000 before 2019 to 0.39 and 0.33/100,000 in 2020 and 2021) in vaccinated and unvaccinated age groups. We did not find a change in vaccine effectiveness against Hib invasive disease (effectiveness > 90%). We discuss factors that may have contributed to this rise.