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

Abstract

Background Haemophilus influenzae serotype b (Hib) conjugate vaccine was introduced in France in 1992 as a 3 + 1 scheme at 2, 3, and 4 months (primary vaccination) with a booster at the age of 16–18 months. The vaccination was simplified in 2013 to a 2 + 1 scheme at 2 and 4 months (primary immunization) and a booster at the age of 11 months. The coverage was 95.4% in France at 24 months in 2017. During the period 2017–2019 the number of Hib invasive infections increased with several cases of vaccine failure. Methods The numbers and proportions of Hib invasive isolates during the period 2017–2019 were compared and vaccine failure cases were explored. A seroprevalence study was performed by measuring anti-polyribosyl-ribitol phosphate (PRP) IgG concentrations by ELISA among children < 5 years of age at the time of sampling covering the periods of the 3 + 1 or 2 + 1 schemes of Hib vaccination. A collection of residual 232 sera was tested (group 3 + 1 n = 130) and (group 2 + 1, n = 102) was used. Results Anti-PRP IgG concentrations were significantly higher in toddlers of 2 years (median 2.9 μg/ml) in the 3 + 1 group while these concentrations showed a median of 0.58 μg/ml among children in 2 + 1 group. The proportion of children of 2 years of age who achieved 1 μg/ml threshold (56%) was higher in the 3 + 1 group than that observed in the 2 + 1 group (25%). All the detected cases of vaccine failure received the 2 + 1 scheme and anti-PRP IgG levels were less than 1 μg/ml at the admission. However, these levels increased significantly 1 month after the admission suggesting a secondary immune response to the Hib infection. Conclusions The simplification of the vaccination to a 2 + 1 scheme seems to reduce the level of anti PRP IgG. Hib antibodies wane rapidly after the 11 months booster and may not be enough to ensure long term protection. Surveillance of cases and monitoring of titres need to be continued to inform future vaccination policy.

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

“…Additionally, the simplification of vaccination strategies in several countries such as France reduced the number of primary doses of vaccines against respiratory pathogens (such as Hi of serotype b, Hib, and Bordetella pertussis ) by switching from the 3 + 1 to 2 + 1 schedule [ 14 ]. These changes in vaccination strategies were suggested to be associated with an increase in the number of B. pertussis and Hib cases [ 15 , 16 ]. The combined effect of all these factors (less bacterial circulation, lower vaccine uptake, and lower number of doses) may have provoked an immunity gap/immunity debt [ 5 ].…”

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

“…New variants of SARS-CoV-2 (2, 3) and decreasing immunity after vaccination over time (4,5), have caused an increased rate of infection and hospitalization even in vaccinated individuals (1). A well-established approach to handle the so-called secondary vaccine failure, is the use of a booster dosean additional vaccine dose after the initial round of immunization (1,6). The effectiveness of a third dose of BioNTech/Pfizer vaccine was suggested by several studies (7)(8)(9).…”

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

“…Haemophilus influenzae type b (Hib) is a fastidious Gram-negative capsulated or non-capsulated bacterium, coccobacillus, that presents a filamentous or pleomorphic shape [ 1 ]. The invasive diseases in childhood cause meningitis, pneumonia and other rarer forms of diseases, such as epiglottitis, septicemia, septic arthritis, bacteremia and cellulitis [ 2 ].…”