Interchangeability of meningococcal group C conjugate vaccines with different carrier proteins in the United Kingdom infant immunisation schedule

Immune responses to typhoid conjugate vaccine in a two dose schedule among Nepalese children <2 years of age

BACKGROUND

Previously, the Vi-typhoid conjugate vaccine (Vi-TT) was found to be highly efficacious in Nepalese children under 16 years of age. We assessed the immunogenicity of Vi-TT at 9 and 12 months of age and response to a booster dose at 15 months of age.

METHODS

Infants were recruited at Patan Hospital, Kathmandu and received an initial dose of Vi-TT at 9 or 12 months of age with a booster dose at 15 months of age. Blood was taken at four timepoints, and antibody titres were measured using a commercial ELISA kit. The primary study outcome was seroconversion (4-fold rise in antibody titre) of IgG one month after both the doses.

FINDINGS

Fifty children were recruited to each study group.Some visits were disrupted by the COVID19 pandemic and occurred out of protocol windows.Both the study groups attained 100 % IgG seroconversion after the initial dose. IgG seroconversion in the 9-month group was significantly higher than in the 12-month group (68.42 % vs 25.8 %, p < 0.001). Among individuals who attended visits per protocol, IgG seroconversion after the first dose occurred in 100 % of individuals (n = 27/27 in 9-month and n = 32/32 in 12-month group). However, seroconversion rates after the second dose were 80 % in the 9-month and 0 % in the shorter dose-interval 12-month group (p < 0.001) (n = 16/20 and n = 0/8, respectively).

INTERPRETATION

Vi-TT is highly immunogenic at both 9 and 12 months of age. Stronger response to a booster in the 9-month group is likely due to the longer interval between doses.

A phase IV, multi-centre, randomized clinical trial comparing two pertussis-containing vaccines in pregnant women in England and vaccine responses in their infants

BACKGROUND

Pertussis vaccines containing three or five pertussis antigens are recommended in pregnancy in many countries, but no studies have compared the effect on infants' antigen-specific immunoglobulin G (IgG) concentrations. The aim of this study was to compare anti-pertussis IgG responses following primary immunization in infants of mothers vaccinated with TdaP₅-IPV (low dose diphtheria toxoid, tetanus toxoid, acellular pertussis [five antigens] and inactivated polio) or TdaP₃-IPV in pregnancy (three pertussis antigens).

METHODS

This multi-centre phase IV randomized clinical trial was conducted in a tertiary referral centre and primary care sites in England. Women were randomized to receive TdaP₅-IPV (n = 77) or TdaP₃-IPV (n = 77) at 28-32 gestational weeks. A non-randomized control group of 44 women who had not received a pertussis-containing vaccine in pregnancy and their 47 infants were enrolled post-partum.

RESULTS

Following infant primary immunization, there was no difference in the geometric mean concentrations (GMCs) of anti-pertussis toxin, filamentous haemagglutinin or pertactin IgG between infants born to women vaccinated with TdaP₅-IPV (n = 67) or TdaP₃-IPV (n = 63). However, the GMC of anti-pertussis toxin IgG was lower in infants born to TdaP₅-IPV- and TdaP₃-IPV-vaccinated mothers compared to infants born to unvaccinated mothers (n = 45) (geometric mean ratio 0.71 [0.56-0.90] and 0.78 [0.61-0.98], respectively); by 13 months of age, this difference was no longer observed.

CONCLUSION

Blunting of anti-pertussis toxin IgG response following primary immunization occurs in infants born to women vaccinated with TdaP₅-IPV and TdaP₃-IPV, with no difference between maternal vaccines. The blunting effect had resolved by 13 months of age. These results may be helpful for countries considering which pertussis-containing vaccine to recommend for use in pregnancy.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT02145624 , registered 23 May 2014.

Immunogenicity and safety of a quadrivalent meningococcal tetanus toxoid-conjugate vaccine (MenACYW-TT) vs. a licensed quadrivalent meningococcal tetanus toxoid-conjugate vaccine in meningococcal vaccine-naïve and meningococcal C conjugate vaccine-primed toddlers: a phase III randomised study

Vaccination remains the best strategy to reduce invasive meningococcal disease. This study evaluated an investigational tetanus toxoid-conjugate quadrivalent meningococcal vaccine (MenACYW-TT) vs. a licensed tetanus toxoid-conjugate quadrivalent meningococcal vaccine (MCV4-TT) (NCT02955797). Healthy toddlers aged 12–23 months were included if they were either meningococcal vaccine-naïve or MenC conjugate (MCC) vaccine-primed (≥1 dose of MCC prior to 12 months of age). Vaccine-naïve participants were randomised 1:1 to either MenACYW-TT (n = 306) or MCV4-TT (n = 306). MCC-primed participants were randomised 2:1 to MenACYW-TT (n = 203) or MCV4-TT (n = 103). Antibody titres against each of the four meningococcal serogroups were measured by serum bactericidal antibody assay using the human complement. The co-primary objectives of this study were to demonstrate the non-inferiority of MenACYW-TT to MCV4-TT in terms of seroprotection (titres ≥1:8) at Day 30 in both vaccine-naïve and all participants (vaccine-naïve and MCC-primed groups pooled). The immune response for all four serogroups to MenACYW-TT was non-inferior to MCV4-TT in vaccine-naïve participants (seroprotection: range 83.6–99.3% and 81.4–91.6%, respectively) and all participants (seroprotection: range 83.6–99.3% and 81.4–98.0%, respectively). The safety profiles of both vaccines were comparable. MenACYW-TT was well-tolerated and demonstrated non-inferior immunogenicity when administered to MCC vaccine-primed and vaccine-naïve toddlers.

Immune response to a Tdap booster in vertically HIV-infected adolescents

BACKGROUND

Pertussis cases have increased worldwide and knowledge on immune response and cytokine profile after Tdap vaccine in immunodeficient adolescents is scarce.

OBJECTIVE

To evaluate the immune response after Tdap in HIV-infected (HIV) and in healthy adolescents (CONTROL).

METHODOLOGY

Thirty HIV adolescents with CD4 cell counts >200 and 30 CONTROLs were immunized with Tdap, after a prior whole-cell DTP vaccine primary scheme. Blood samples were collected immediately before and after vaccine. Lymphocyte immunophenotyping was performed by flow cytometry; tetanus, diphtheria and pertussis toxin antibodies were assessed by ELISA; whole blood was stimulated with tetanus toxoid and Bordetella pertussis and supernatants were assessed for cytokines by xMAP.

RESULTS

Mean age of HIV and CONTROL groups were 17.9 e 17.1 years, respectively. Pain at injection site was more intense in CONTROL group. HIV group had similar increase in tetanus antibodies at 28 days (geometric mean concentration, GMC, 15.6; 95% CI, 7.52-32.4) than CONTROL group (GMC, 23.1; 95% CI, 15.0-35.5), but lower diphtheria antibodies at 28 days (GMC, 2.3; 95% CI, 0.88-6.19) than CONTROL group (GMC, 16.4; 95% CI, 10.3-26.2); for pertussis, the percentage of individuals who seroconverted was lower in HIV than CONTROL group (HIV, 62.1% versus CONTROL, 100%; p = .002). Both groups built a cellular immune response to tetanus, with a Th2 (IL-4, IL-5 and IL-13) and Th1 (IFN-γ) response, with lower cytokine levels in HIV than in CONTROL group. Especially for pertussis, cellular and humoral responses were less intense in HIV adolescents, with a lower Th1 and Th17 profile and higher IL-10 levels. HIV-infected adolescents on viral suppression showed an enhanced immune response to all the three vaccine antigens, although still at lower levels if compared to CONTROL group.

CONCLUSIONS

Both groups tolerated well and built an immune response after Tdap. However, HIV-infected adolescents would probably benefit from more frequent booster doses.

Meningococcal disease and control in China: Findings and updates from the Global Meningococcal Initiative (GMI)

The Global Meningococcal Initiative (GMI) is a global expert group, including scientists, clinicians and public health officials from a wide range of specialities. The goal of the GMI is to prevent meningococcal disease worldwide through education, research, and co-operation. The Chinese GMI roundtable meeting was held in June 2017. The GMI met with local experts to gain insight into the meningococcal disease burden in China and current prevention and vaccination strategies in place. China experienced five epidemics of serogroup A meningococcal disease (MenA) between 1938 and 1977, with peak incidence of 403/100,000 recorded in 1967. MenA incidence rates have significantly declined following the universal introduction of the MenA polysaccharide vaccine in China in the 1980s. Further, surveillance data indicates changing meningococcal epidemiology in China with the emergence of new clones of serogroup B from serogroup C clonal complex (cc) 4821 due to capsular switching, and the international spread of serogroup W cc11. The importance of carriage and herd protection for controlling meningococcal disease was highlighted with the view to introduce conjugate vaccines and serogroup B vaccines into the national immunization schedule. Improved disease surveillance and standardized laboratory techniques across and within provinces will ensure optimal epidemiological monitoring.

Interplay of Carbohydrate and Carrier in Antibacterial Glycoconjugate Vaccines

Bacterial infections are a serious health concern and are responsible for millions of illnesses and deaths each year in communities around the world. Vaccination is an important public health measure for reducing and eliminating this burden, and regions with comprehensive vaccination programs have achieved significant reductions in infection and mortality. This is often accomplished by immunization with bacteria-derived carbohydrates, typically in conjunction with other biomolecules, which induce immunological memory and durable protection against bacterial human pathogens. For many species, however, vaccines are currently unavailable or have suboptimal efficacy characterized by short-lived memory and incomplete protection, especially among at-risk populations. To address this challenge, new tools and techniques have emerged for engineering carbohydrates and conjugating them to carrier molecules in a tractable and scalable manner. Collectively, these approaches are yielding carbohydrate-based vaccine designs with increased immunogenicity and protective efficacy, thereby opening up new opportunities for this important class of antigens. In this chapter we detail the current understanding of how carbohydrates interact with the immune system to provide immunity; how glycoengineering, especially in the context of glycoconjugate vaccines, can be used to modify and enhance immune responses; and current trends and strategies being pursued for the rational design of next-generation glycosylated antibacterial vaccines. Graphical Abstract.

Interactions of conjugate vaccines and co-administered vaccines

Conjugate vaccines play an important role in the prevention of infectious diseases such as those caused by the bacteria Haemophilus influenzae (Hi) type b (Hib), Neisseria meningitidis, and Streptococcus pneumoniae. Vaccines developed against these 3 pathogens utilize 3 main carrier proteins, non-toxic mutant of diphtheria toxin (CRM197), diphtheria toxoid (DT) and tetanus toxoid (TT). Current pediatric immunisation schedules include the administration of several vaccines simultaneously, therefore increasing the potential for immune interference (both positively and negatively) to the antigens administered. Knowledge of vaccine interactions is principally derived from clinical trials, these are reviewed here to explore immune interference which may result of from carrier-specific T-cell helper interactions, bystander interference and carrier induced epitopic suppression.

Do Dose Numbers Matter?: Evaluation of Differing Infant and Toddler Meningococcal C Conjugate Vaccine Programs in Canadian Children

BACKGROUND

The diversity of Canadian infant meningococcal C conjugate (MenC) vaccine programs is unique among countries providing MenC vaccines and offers a valuable opportunity to determine the optimal vaccine program. This longitudinal study assessed differences in seroprotection by 3 different vaccine schedules in children two years after receiving either 1 toddler MenC vaccine dose (1 dose), 1 infant and 1 toddler dose (2 doses), or 2 infant and 1 toddler MenC vaccine dose (3 doses).

METHODS

Three similar cohorts of healthy infants from 1, 2 and 3 dose program areas were enrolled before to their 12 month toddler dose and vaccinated with MenC-tetanus toxoid (MenC-TT) conjugate vaccine. Sera obtained 2 years later were assayed for serogroup C bactericidal activity using standardized procedures with rabbit as the exogenous complement source. Serum bactericidal activity titers ≥1:8 were considered protective.

RESULTS

Results were available for 384 children. Rates of seroprotection at 36 months of age were significantly different between the 1 and 3 dose programs, but confidence intervals overlapped between the 1 and 2 dose programs and between the 2 and 3 dose programs: 1 dose 92% (95% confidence interval: 86%-96%) versus 99% (95%-100%) with 2 doses and 100% (97%-100%) with 3 doses. Geometric mean titers were significantly different at 12.1 (10.8-13.5), 32.4 (28.9-36.2) and 50.6 (45.7-55.9) in the 1, 2 and 3 dose programs, respectively.

CONCLUSIONS

At 36 months of age, evidence of seroprotection remained for greater than 90% of participants. Our results indicate that 1 toddler dose or 1 infant plus 1 toddler dose with MenC-TT vaccine provides seroprotection against MenC disease in early childhood.

Schedules for Pneumococcal Vaccination of Preterm Infants: An RCT

BACKGROUND AND OBJECTIVE

Premature infants have a higher risk of invasive pneumococcal disease and are more likely to have lower vaccine responses compared with term infants. Increasingly, immunization schedules are including a reduced, 2-dose, pneumococcal conjugate vaccine priming schedule. Our goal was to assess the immunogenicity of 3 commonly used 13-valent pneumococcal conjugate vaccine (PCV13) priming schedules in premature infants and their response to a 12-month booster dose.

METHODS

Premature infants (<35 weeks' gestation) were randomized to receive PCV13 at 2 and 4 months (reduced schedule); 2, 3, and 4 months (accelerated schedule); or 2, 4, and 6 months (extended schedule). All infants received a 12-month PCV13 booster. Serotype-specific pneumococcal immunoglobulin G (IgG) for PCV13 serotypes was measured by using enzyme-linked immunosorbent assay 1 month after the primary and booster vaccinations.

RESULTS

A total of 210 infants (median birth gestation, 29(+6) weeks; range, 23(+2)-34(+6) weeks) were included. After the primary vaccination, 75% (95% confidence interval [CI], 62-85), 88% (95% CI, 76-95), and 97% (95% CI, 87-99) of participants had protective antibody concentrations for at least one-half the PCV13 serotypes for the reduced, accelerated, and extended schedules, respectively. After the booster vaccination, participants receiving the extended schedule had significantly lower (P < .05) geometric mean concentrations compared with reduced (for 9 of 13 serotypes) and accelerated (for 4 of 13 serotypes) schedules, but nearly all participations, regardless of schedule or serotype, had seroprotective IgG concentrations.

CONCLUSIONS

A reduced priming schedule of PCV13 resulted in higher post-booster IgG concentrations but lower post-primary concentrations. The optimum vaccine schedule for preterm infants will therefore depend on when they are most at risk for invasive pneumococcal disease.

Antibody responses after primary immunization in infants born to women receiving a pertussis-containing vaccine during pregnancy: single arm observational study with a historical comparator

INTRODUCTION

In England, antenatal pertussis immunization using a tetanus/low-dose diphtheria/5-component acellular-pertussis/inactivated-polio (TdaP5/IPV) vaccine was introduced in October 2012. We assessed infant responses to antigens in the maternal vaccine and to those conjugated to tetanus (TT) or the diphtheria toxin variant, CRM.

METHODS

Infants of 141 TdaP5/IPV-vaccinated mothers in Southern England immunized with DTaP5/IPV/Haemophilus influenzae b (Hib-TT) vaccine at 2-3-4 months, 13-valent pneumococcal vaccine (PCV13, CRM-conjugated) at 2-4 months and 1 or 2 meningococcal C vaccine (MCC-CRM- or MCC-TT) doses at 3-4 months had blood samples taken at 2 and/or 5 months of age.

RESULTS

Antibody responses to pertussis toxin (PT), filamentous hemagglutinin (FHA), fimbriae 2 + 3 (FIMs), diphtheria, tetanus, Hib, MCC and PCV13 serotypes were compared to responses in a historical cohort of 246 infants born to mothers not vaccinated in pregnancy. Infants had high pertussis antibody concentrations pre-immunization but only PT antibodies increased post-immunization (fold-change, 2.64; 95% confidence interval [CI], 2.12-3.30; P < .001), whereas FHA antibodies fell (fold-change, 0.56; 95% CI, .48-.65; P < .001). Compared with infants of unvaccinated mothers, PT, FHA, and FIMs antibodies were lower post-vaccination, with fold-differences of 0.67 (0.58-0.77; P < .001), 0.62 (0.54-0.71; P < .001) and 0.51 (0.42-0.62; P < .001), respectively. Antibodies to diphtheria and some CRM-conjugated antigens were also lower, although most infants achieved protective thresholds; antibodies to tetanus and Hib were higher.

CONCLUSIONS

Antenatal pertussis immunization results in high infant pre-immunization antibody concentrations, but blunts subsequent responses to pertussis vaccine and some CRM-conjugated antigens. In countries with no pertussis booster until school age, continued monitoring of protection against pertussis is essential.

Is a single infant priming dose of meningococcal serogroup C conjugate vaccine in the United Kingdom sufficient?

In 1999, the UK introduced meningococcal serogroup C conjugate (MCC) vaccination at 2, 3, 4 months of age with a single dose for children 1-18 y In 2006, the schedule was refined to a 2 dose priming schedule with a booster in the second year of life. In 2013, the number of priming doses was reduced to a single priming dose, the booster maintained at 12 months of age and an adolescent booster dose introduced. The paper presents the evidence supporting the reduction in the number of priming doses. A UK study provided evidence for reducing the priming doses of MCC-TT together with the positive correlation of lower quantity of antigen and serum bactericidal antibody (SBA) levels post-primary but a higher magnitude of the booster response. Another UK study, demonstrated one dose of MCC-TT or MCC-CRM197 at 3 months gave comparable responses to 2 doses (SBA titres ≥8) both post-primary vaccination and post-booster Hib/MCC-TT at 12 months. However, the magnitude of the SBA GMT was higher in the MCC-TT primed post-booster. A single priming dose of MCC-TT (at 4 or 6 months) compared to 2 doses (2 and 4 months) gave higher SBA titres in all groups, post-primary and post-booster at 12-13 months, with the highest SBA responses observed in the 4 month single dose group. A study in Malta, comparing one dose of MCC-TT or MCC-CRM197 at (3 months) versus 2 doses of MCC-CRM197 (3 and 4 months), showed a high proportion (>84.72%) of subjects achieving SBA titres ≥8 following a single dose. These studies show that a single-dose priming MCC vaccination in infancy is sufficient.