MenAfriVac as an Antitetanus Vaccine

Immune responses against group B Streptococcus monovalent and pentavalent capsular polysaccharide tetanus toxoid conjugate vaccines in Balb/c mice

Immunization of pregnant women with Group B Streptococcus (GBS) capsular polysaccharide (CPS) conjugate vaccine (CV) could protect young infants against invasive GBS disease. We evaluated the immunogenicity of investigational five GBS monovalent (serotypes Ia, Ib, II, III, and V) CPS-tetanus toxoid (TT)-CV with adjuvant and GBS pentavalent CPS-TT-CV with adjuvant (GBS5-CV-adj) and without adjuvant (GBS5-CV-no-adj), in Balb/c mice. Aluminum phosphate was the adjuvant in the formulations, where included. The homotypic immunoglobulin G (IgG) geometric mean concentration (GMC) and opsonophagocytic activity (OPA) geometric mean titer (GMT) did not differ after the third dose of the GBS5-CV-adj vaccine compared with the monovalent counterparts for all five serotypes. The GBS5-CV-adj induced higher post-vaccination serotype-specific IgG GMCs and OPA GMTs compared to GBS5-CV-no_adj. The GBS5-CV with and without adjuvant should be considered for further development as a potential vaccine for pregnant women to protect their infants against invasive GBS disease.

Field investigation of high reported non-neonatal tetanus burden in Uganda, 2016-2017

BACKGROUND

Despite providing tetanus-toxoid-containing vaccine (TTCV) to infants and reproductive-age women, Uganda reports one of the highest incidences of non-neonatal tetanus (non-NT). Prompted by unusual epidemiologic trends among reported non-NT cases, we conducted a retrospective record review to see whether these data reflected true disease burden.

METHODS

We analysed nationally reported non-NT cases during 2012-2017. We visited 26 facilities (14 hospitals, 12 health centres) reporting high numbers of non-NT cases (n = 20) or zero cases (n = 6). We identified non-NT cases in facility registers during 1 January 2016-30 June 2017; the identified case records were abstracted.

RESULTS

During 2012-2017, a total of 24 518 non-NT cases were reported and 74% were ≥5 years old. The average annual incidence was 3.43 per 100 000 population based on inpatient admissions. Among 482 non-NT inpatient cases reported during 1 January 2016-30 June 2017 from hospitals visited, 342 (71%) were identified in facility registers, despite missing register data (21%). Males comprised 283 (83%) of identified cases and 60% were ≥15 years old. Of 145 cases with detailed records, 134 (92%) were clinically confirmed tetanus; among these, the case-fatality ratio (CFR) was 54%. Fourteen cases were identified at two hospitals reporting zero cases. Among >4000 outpatient cases reported from health centres visited, only 3 cases were identified; the remainder were data errors.

CONCLUSIONS

A substantial number of non-NT cases and deaths occur in Uganda. The high CFR and high non-NT burden among men and older children indicate the need for TTCV booster doses across the life course to all individuals as well as improved coverage with the TTCV primary series. The observed data errors indicate the need for data quality improvement activities.

Tetanus and Diphtheria Seroprotection among Children Younger Than 15 Years in Nigeria, 2018: Who Are the Unprotected Children?

Serological surveys provide an objective biological measure of population immunity, and tetanus serological surveys can also assess vaccination coverage. We undertook a national assessment of immunity to tetanus and diphtheria among Nigerian children aged <15 years using stored specimens collected during the 2018 Nigeria HIV/AIDS Indicator and Impact Survey, a national cross-sectional household-based survey. We used a validated multiplex bead assay to test for tetanus and diphtheria toxoid-antibodies. In total, 31,456 specimens were tested. Overall, 70.9% and 84.3% of children aged <15 years had at least minimal seroprotection (≥0.01 IU/mL) against tetanus and diphtheria, respectively. Seroprotection was lowest in the north west and north east zones. Factors associated with increased tetanus seroprotection included living in the southern geopolitical zones, urban residence, and higher wealth quintiles (p < 0.001). Full seroprotection (≥0.1 IU/mL) was the same for tetanus (42.2%) and diphtheria (41.7%), while long-term seroprotection (≥1 IU/mL) was 15.1% for tetanus and 6.0% for diphtheria. Full- and long-term seroprotection were higher in boys compared to girls (p < 0.001). Achieving high infant vaccination coverage by targeting specific geographic areas and socio-economic groups and introducing tetanus and diphtheria booster doses in childhood and adolescence are needed to achieve lifelong protection against tetanus and diphtheria and prevent maternal and neonatal tetanus.

Sustaining Maternal and Neonatal Tetanus Elimination (MNTE) in countries that have been validated for elimination - progress and challenges

BACKGROUND

As of October 2021, 47 (80%) of the 59 countries, identified at highest risk for Maternal and Neonatal Tetanus (MNT), had been validated for elimination. We assessed sustainability of MNT elimination (MNTE) in 28 countries that were validated during 2011‒2020.

METHODS

We assessed the attainment of the following MNTE sustainability indicators: 1) ≥ 90% coverage with three doses of Diphtheria-Tetanus-Pertussis vaccine (DTP3) among infants < 1 year, 2) ≥ 80% coverage with at least two doses of tetanus toxoid-containing vaccine (TTCV2 +) among pregnant women, 3) ≥ 80% protection at birth (PAB), 4) ≥ 70% skilled birth attendance (SBA), and 4) ≥ 80% first (ANC1) and fourth antenatal care (ANC4) visits. We assessed the introduction of TTCV booster doses. Data sources included the 2020 WHO /UNICEF Joint Reporting Forms, and the latest Demographic and Health Survey (DHS) or Multi-Indicator Cluster Surveys (MICS) for each country, if available. We reviewed literature and used DHS/MICS data to identify barriers to sustaining MNTE.

RESULTS

Of 28 assessed countries, 7 (25%) reported ≥ 90% DTP3 coverage, 4 of 26 (16%) reported ≥ 80% TTCV2 + coverage, and 23 of 27 (85%) reported ≥ 80% PAB coverage. Based on DHS/MICS in 15 of the 28 countries, 10 (67%) achieved ≥ 70% SBA delivery, 13 (87%) achieved ≥ 80% ANC1 visit coverage, and 3 (20%) ≥ 80% ANC4 visit coverage. We observed sub-optimal coverage in many countries at the subnational level. The first, second and third booster doses of TTCV respectively have been introduced in 6 (21%), 5 (18%), and 1 (4%) of 28 countries. Only three countries conducted post-MNTE validation assessments. Barriers to MNTE sustainability included: competing program priorities, limited resources to introduce TTCV booster doses and implement corrective immunization in high-risk districts and socio-economic factors.

CONCLUSIONS

Despite good performance of MNTE indicators in several countries, MNTE sustainability appears threatened in some countries. Integration and coordination of MNTE activities with other immunization activities in the context of the Immunization Agenda 2030 lifecourse vaccination strategy such as providing tetanus booster doses in school-based vaccination platforms, during measles second dose and HPV vaccination, and integrating MNTE post-validation assessments with immunization program reviews will ensure MNTE is sustained.

Developing an Effective Glycan-based Vaccine for Streptococcus Pyogenes

Streptococcus pyogenes is a primary infective agent that causes approximately 700 million human infections each year, resulting in more than 500,000 deaths. Carbohydrate-based vaccines are proven to be one of the most promising subunit vaccine candidates, as the bacterial glycan pattern(s) are different from mammalian cells and show increased pathogen serotype conservancy than the protein components. In this review we highlight reverse vaccinology for use in the development of subunit vaccines against S. pyogenes, and report reproducible methods of carbohydrate antigen production, in addition to the structure-immunogenicity correlation between group A carbohydrate epitopes and alternative vaccine antigen carrier systems. We also report recent advances used to overcome hurdles in carbohydrate-based vaccine development.

Immunogenicity and safety of a quadrivalent meningococcal tetanus toxoid-conjugate vaccine (MenACYW-TT) in healthy toddlers: a Phase II randomized study

NEISSERIA MENINGITIDIS

can lead to invasive meningococcal disease to which young children are particularly vulnerable. We assessed the immunogenicity and safety of Sanofi Pasteur's investigational quadrivalent (serogroups A, C, Y, and W) meningococcal tetanus-toxoid conjugate vaccine, MenACYW-TT, as a single dose, in healthy meningococcal vaccine-naïve toddlers versus a licensed conjugate vaccine MCV4-TT (NCT03205358). In this Phase II study conducted in Finland, 188 toddlers aged 12-24 months were randomized 1:1 to MenACYW-TT or MCV4-TT. Serum bactericidal antibody assays using human complement (hSBA) and baby rabbit complement (rSBA) measured antibodies against each serogroup before and 30 days after vaccination. Participants were monitored for immediate adverse events (AEs) and post-vaccination AEs for 30 days. All analyses were descriptive. All 188 participants completed the study. The Day 30 hSBA seroresponses (hSBA titer <8 at baseline and post-vaccination titer ≥8, or ≥8 at baseline and ≥4-fold increase post-vaccination) were comparable between participants receiving MenACYW-TT (96.7-100%), and MCV4-TT (86.0-100.0%) for each serogroup. Most unsolicited AEs were of Grade 1 or Grade 2 intensity. There were no immediate hypersensitivity reactions, and no AEs or serious AEs leading to discontinuation from the study. In this exploratory study, MenACYW-TT vaccine was well tolerated and immunogenic. If confirmed in Phase III, a single dose of the MenACYW-TT vaccine may show promise as an alternative vaccine option for toddlers receiving meningococcal vaccination for the first time.

Tetanus

Tetanus is a vaccine-preventable disease that still commonly occurs in many low-income and middle-income countries, although it is rare in high-income countries. The disease is caused by the toxin of the bacterium Clostridium tetani and is characterised by muscle spasms and autonomic nervous system dysfunction. Global vaccination initiatives have had considerable success but they continue to face many challenges. Treatment for tetanus aims to control spasms and reduce cardiovascular instability, and consists of wound debridement, antitoxin, antibiotics, and supportive care. Recent research has focused on intravenous magnesium sulphate and intrathecal antitoxin administration as methods of spasm control that can avoid the need for ventilatory support. Nevertheless, without access to mechanical ventilation, mortality from tetanus remains high. Even with such care, patients require several weeks of hospitalisation and are vulnerable to secondary problems, such as hospital-acquired infections.

Integrating Blood Collection within Household Surveys: Lessons Learned from Nesting a Measles and Rubella Serological Survey within a Post-Campaign Coverage Evaluation Survey in Southern Province, Zambia

Age-specific population immunity to many vaccine-preventable diseases can be measured using serological surveys. However, stand-alone serological surveys are infrequently conducted in low- and middle-income countries because of costs, operational challenges, and potential high refusal rates for blood collection. Nesting a serosurvey within a household cluster survey may overcome some of these challenges. We share lessons learned from nesting a serosurvey within a measles and rubella vaccination post-campaign coverage evaluation survey (PCES). In 15 of the 26 PCES clusters in Southern Province, Zambia, we collected dried blood spots from 581 participants aged 9 months and older. Household participation rates for the main PCES were higher in the serosurvey clusters (86%) than PCES-only clusters (71%), suggesting that a serosurvey can be successfully integrated without adversely affecting PCES participation. Among households that participated in the PCES, 80% also participated in the serosurvey and 86% of individuals available in the household provided a blood sample for the serosurvey. Substantial planning and coordination, additional staff training, and community mobilization were critical to the success of the serosurvey. Most challenges stemmed from using different data collecting tools and teams for the serosurvey and PCES. A more efficient design would be to fully integrate the serosurvey by adding blood collection and additional questions to the PCES.

Developmental strategy for a new Group A meningococcal conjugate vaccine (MenAfriVacR)

Until recently, periodic Group A meningococcal meningitis outbreaks were a major public health problem in the sub-Saharan Africa. In 2001, the Meningitis Vaccine Project (MVP), a partnership between the World Health Organization (WHO) and PATH, a Seattle-based NGO, and the Serum Institute of India Pvt Ltd (SIIPL) initiated discussions aimed at establishing a collaboration to develop a Group A meningococcal conjugate vaccine for this unmet medical need. Over the next 8 years the partnership made countless strategic decisions about product characteristics, raw materials, potential target populations, geographic prioritization and affordability of the vaccine to name a few. These decisions evolved into detailed plans for preclinical development, extensive field trials in Africa and India and a focused regulatory strategy specific for the Men A conjugate vaccine. Important characteristics of the process included, flexibility, transparency andeffective partnerships that included public agencies as well as private companies in Africa, Europe, the United States and India.

Progress towards achieving and maintaining maternal and neonatal tetanus elimination in the African region

Despite the availability of effective tetanus prevention strategies, as of 2016, Maternal and Neonatal Tetanus Elimination (MNTE) has not yet been achieved in 18 countries globally. In this paper, we review the status of MNTE in the World Health Organization African Region (AFR),and provide recommendations for achieving and maintaining MNTE in AFR. As of November 2016, 37 (79%) AFR countries have achieved MNTE, with 10 (21%) countries remaining. DTP3 coverage increased from 52% in 2000 to 76% in 2015. In 2015, coverage with at least 2 doses of tetanus containing vaccine (TT2+) and proportion of newborns protected at birth (PAB) were 69% and 77%, compared with 44% and 62% in 2000, respectively. Since 1999, over 79 million women of reproductive age (WRA) have been vaccinated with TT2+ through supplementary immunization activities (SIAs). Despite the progress, only 54% of births were attended by skilled birth attendants (SBAs), 5 (11%) countries provided the 3 WHO-recommended booster doses to both sexes, and about 5.5 million WRA still need to be reached with SIAs. Coverage disparities still exist between countries that have achieved MNTE and those that have not. In 2015, coverage with DTP3 and PAB were higher in MNTE countries compared with those yet to achieve MNTE: 84% vs. 68% and 86% vs. 69%, respectively. Challenges to achieving MNTE in the remaining AFR countries include weak health systems, competing priorities, insufficient funding, insecurity, and sub-optimal neonatal tetanus (NT) surveillance. To achieve and maintain MNTE in AFR, increasing SBAs and tetanus vaccination coverage, integrating tetanus vaccination with other opportunities (e.g., polio and measles campaigns, mother and child health days), and providing appropriately spaced booster doses are needed. Strengthening NT surveillance and conducting serosurveys would ensure appropriate targeting of MNTE activities and high-quality information for validating the achievement and maintenance of elimination.

Polysaccharide conjugate vaccine protein carriers as a "neglected valency" - Potential and limitations

The development of vaccines against polysaccharide-encapsulated pathogens (e.g. Haemophilus influenzae type b, pneumococci, meningococci) is challenging because polysaccharides do not elicit a strong and long-lasting immune response (i.e. T-cell independent). This can be overcome by conjugating the polysaccharide to a protein carrier (e.g. tetanus toxoid, cross-reacting material 197 [CRM]), which vastly improves the immune response and induces memory to the polysaccharide (T-cell dependent). Although it is well documented that protein carriers additionally induce an immune response against themselves, this potential "additional valency" has so far not been recognized. The only exception is for the protein D carrier (derived from non-typeable Haemophilus influenzae [NTHi]) used in a pneumococcal conjugate vaccine, which may have a beneficial impact on NTHi acute otitis media. In this review, we describe the immunogenicity of various protein carriers and discuss their potential dual function: as providers of T-cell helper epitopes and as protective antigens. If this "additional valency" could be proven to be protective, it may be possible to consider its potential effect on the number of required immunizations. We also describe the potential for positive or negative interference between conjugate vaccines using the same protein carriers, the resulting desire for novel carriers, and information on potential new carriers. The range of conjugate vaccines is ever expanding, with different carriers and methods of conjugation. We propose that new conjugate vaccine trials should assess immunogenicity to both the polysaccharide and carrier. Ultimately, this so-far "neglected valency" could be an exploitable characteristic of polysaccharide conjugate vaccines.

Meningococcal disease in the Middle East and Africa: Findings and updates from the Global Meningococcal Initiative

The Global Meningococcal Initiative (GMI) has recently considered current issues in Middle Eastern and African countries, and produced two recommendations: (i) that vaccination of attendees should be considered for some types of mass-gathering events, as some countries mandate for the Hajj, and (ii) vaccination of people with human immunodeficiency virus should be used routinely, because of increased meningococcal disease (MD) risk. Differences exist between Middle Eastern and African countries regarding case and syndrome definitions, surveillance, and epidemiologic data gaps. Sentinel surveillance provides an overview of trends and prevalence of different capsular groups supporting vaccine selection and planning, whereas cost-effectiveness decisions require comprehensive disease burden data, ideally counting every case. Surveillance data showed importance of serogroup B MD in North Africa and serogroup W expansion in Turkey and South Africa. Success of MenAfriVac^® in the African "meningitis belt" was reviewed; the GMI believes similar benefits may follow development of a low-cost meningococcal pentavalent vaccine, currently in phase 1 clinical trial, by 2022. The importance of carriage and herd protection for controlling invasive MD and the importance of advocacy and awareness campaigns were also highlighted.

Higher Tetanus Toxoid Immunity 2 Years After PsA-TT Introduction in Mali

Background. In 2010, mass vaccination with a then-new meningococcal A polysaccharide–tetanus toxoid protein conjugate vaccine (PsA-TT, or MenAfriVac) was undertaken in 1- to 29-year-olds in Bamako, Mali. Whether vaccination with PsA-TT effectively boosts tetanus immunity in a population with heterogeneous baseline tetanus immunity is not known. We assessed the impact of PsA-TT on tetanus toxoid (TT) immunity by quantifying age- and sex-specific immunity prior to and 2 years after introduction.

Methods. Using a household-based, age-stratified design, we randomly selected participants for a prevaccination serological survey in 2010 and a postvaccination survey in 2012. TT immunoglobulin G (IgG) antibodies were quantified and geometric mean concentrations (GMCs) pre- and postvaccination among all age groups targeted for vaccination were compared. The probability of TT IgG levels ≥0.1 IU/mL (indicating short-term protection) and ≥1.0 IU/mL (indicating long-term protection) by age and sex was determined using logistic regression models.

Results. Analysis of 793 prevaccination and 800 postvaccination sera indicated that while GMCs were low pre–PsA-TT, significantly higher GMCs in all age–sex strata were observed 2 years after PsA-TT introduction. The percentage with short-term immunity increased from 57.1% to 88.4% (31.3-point increase; 95% confidence interval [CI], 26.6–36.0;, P < .0001) and with long-term immunity increased from 20.0% to 58.5% (38.5-point increase; 95% CI, 33.7–43.3; P < .0001) pre- and postvaccination.

Conclusions. Significantly higher TT immunity was observed among vaccine-targeted age groups up to 2 years after Mali's PsA-TT mass vaccination campaign. Our results, combined with evidence from clinical trials, strongly suggest that conjugate vaccines containing TT such as PsA-TT should be considered bivalent vaccines because of their ability to boost tetanus immunity.

Seroepidemiology: an underused tool for designing and monitoring vaccination programmes in low- and middle-income countries

Seroepidemiology, the use of data on the prevalence of bio-markers of infection or vaccination, is a potentially powerful tool to understand the epidemiology of infection before vaccination and to monitor the effectiveness of vaccination programmes. Global and national burden of disease estimates for hepatitis B and rubella are based almost exclusively on serological data. Seroepidemiology has helped in the design of measles, poliomyelitis and rubella elimination programmes, by informing estimates of the required population immunity thresholds for elimination. It contributes to monitoring of these programmes by identifying population immunity gaps and evaluating the effectiveness of vaccination campaigns. Seroepidemiological data have also helped to identify contributing factors to resurgences of diphtheria, Haemophilus Influenzae type B and pertussis. When there is no confounding by antibodies induced by natural infection (as is the case for tetanus and hepatitis B vaccines), seroprevalence data provide a composite picture of vaccination coverage and effectiveness, although they cannot reliably indicate the number of doses of vaccine received. Despite these potential uses, technological, time and cost constraints have limited the widespread application of this tool in low-income countries. The use of venous blood samples makes it difficult to obtain high participation rates in surveys, but the performance of assays based on less invasive samples such as dried blood spots or oral fluid has varied greatly. Waning antibody levels after vaccination may mean that seroprevalence underestimates immunity. This, together with variation in assay sensitivity and specificity and the common need to take account of antibody induced by natural infection, means that relatively sophisticated statistical analysis of data is required. Nonetheless, advances in assays on minimally invasive samples may enhance the feasibility of including serology in large survey programmes in low-income countries. In this paper, we review the potential uses of seroepidemiology to improve vaccination policymaking and programme monitoring and discuss what is needed to broaden the use of this tool in low- and middle-income countries.

Factors contributing to the immunogenicity of meningococcal conjugate vaccines

Various glycoprotein conjugate vaccines have been developed for the prevention of invasive meningococcal disease, having significant advantages over pure polysaccharide vaccines. One of the most important features of the conjugate vaccines is the induction of a T-cell dependent immune response, which enables both the induction of immune memory and a booster response after repeated immunization. The nature of the carrier protein to which the polysaccharides are chemically linked, is often regarded as the main component of the vaccine in determining its immunogenicity. However, other factors can have a significant impact on the vaccine's profile. In this review, we explore the physico-chemical properties of meningococcal conjugate vaccines, which can significantly contribute to the vaccine's immunogenicity. We demonstrate that the carrier is not the sole determining factor of the vaccine's profile, but, moreover, that the conjugate vaccine's immunogenicity is the result of multiple physico-chemical structures and characteristics.