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•To avoid a global pertussis resurgence, booster Tdap immunization is recommended.•Global shortages of acellular pertussis vaccines have been reported.•Safety and immunogenicity of SIIPL Tdap was compared to an approved Tdap vaccine.•SIIPL Tdap immune responses were non-inferior to comparator Tdap vaccine.•SIIPL Tdap was safe and well tolerated. This study assessed the safety and immunogenicity of a new booster vaccine against tetanus, diphtheria, and pertussis manufactured by Serum Institute of India Pvt. Ltd (SIIPL Tdap). The Phase II/III trial was randomized (2:1), observer blinded and active controlled. Healthy subjects aged 4–65 years received a single dose of either SIIPL Tdap or comparator Tdap vaccine (Boostrix®, GlaxoSmithKline, Belgium), and were followed-up for 30 days. Blood samples for safety and immunogenicity assessments were collected pre-vaccination and on day 30 post-vaccination. The study assessed safety and reactogenicity of SIIPL Tdap compared to the comparator Tdap as well as the co-primary immunogenicity outcomes: (i) seroprotection rates against diphtheria toxoid (DT) and tetanus toxoid (TT) and (ii) the booster response rates against pertussis toxoid (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) 30 days post-vaccination in all study subjects. A margin of −10 % was used for non-inferiority testing. Secondary outcomes included the booster response rates against DT and TT, seropositivity rates against pertussis antigens, and antibody geometric mean concentrations (GMCs) for all vaccine components. At Day 30 post-vaccination, SIIPL Tdap was assessed as non-inferior to the comparator Tdap in terms of: i) seroprotection rates against DT (94.4 % vs. 94.9 %) and TT (99.9 % vs. 100 %) and ii) pertussis booster response rates (93.8 % vs. 88.4 % anti-PT, 89.7 % vs. 90.9 % anti-FHA and 86.3 % vs. 84.4 % anti-PRN), for SIIPL Tdap versus comparator Tdap, respectively. GMCs for anti-PT and anti-PRN were higher in subjects vaccinated with SIIPL Tdap compared to comparator Tdap. All other secondary outcomes were comparable. The overall frequency of local and systemic solicited AEs was comparable; no treatment related SAEs were reported. Booster vaccination with SIIPL Tdap was non-inferior to comparator Tdap with respect to the immunogenicity of the vaccine components and was equally well tolerated. EudraCT number: 2019-002706-46.

Clostridium difficile, a major cause of nosocomial and antibiotic-associated diarrhea, carries a significant disease and cost burden. This study aimed to select an optimal formulation and schedule for a candidate toxoid vaccine against C. difficile toxins A and B. Randomized, placebo-controlled, two-stage, Phase 2 study in a total of 661 adults aged 40–75 years. Stage I: low (50μg antigen) or high (100μg antigen) dose with or without aluminum hydroxide (AlOH) adjuvant, or placebo, administered on Days 0–7–30. Stage II: Days 0–7–30, 0–7–180, and 0–30–180, using the formulation selected in Stage I through a decision tree defined a priori and based principally on a bootstrap ranking approach. Administration was intramuscular. Blood samples were obtained on Days 0, 7, 14, 30, 60 (Stage I and II), 180, and 210 (Stage II); IgG to toxins A and B was measured by ELISA and in vitro functional activity was measured by toxin neutralizing assay (TNA). Safety data were collected using diary cards. In Stage I the composite immune response against toxins A and B (percentage of participants who seroconverted for both toxins) was highest in the high dose+adjuvant group (97% and 92% for Toxins A and B, respectively) and was chosen for Stage II. In Stage II the immune response profile for this formulation through Day 180 given on Days 0–7–30 ranked above the other two administration schedules. There were no safety issues. The high dose+adjuvant (100μg antigen+AlOH) formulation administered at 0–7–30 days elicited the best immune response profile, including functional antibody responses, through Day 180 and was selected for use in subsequent clinical trials.

Typhoid fever remains a major cause of morbidity and mortality in low-income and middle-income countries. Vi-tetanus toxoid conjugate vaccine (Vi-TT) is recommended by WHO for implementation in high-burden countries, but there is little evidence about its ability to protect against clinical typhoid in such settings. We did a participant-masked and observer-masked cluster-randomised trial preceded by a safety pilot phase in an urban endemic setting in Dhaka, Bangladesh. 150 clusters, each with approximately 1350 residents, were randomly assigned (1:1) to either Vi-TT or SA 14-14-2 Japanese encephalitis (JE) vaccine. Children aged 9 months to less than 16 years were invited via parent or guardian to receive a single, parenteral dose of vaccine according to their cluster of residence. The study population was followed for an average of 17·1 months. Total and overall protection by Vi-TT against blood culture-confirmed typhoid were the primary endpoints assessed in the intention-to-treat population of vaccinees or all residents in the clusters. A subset of approximately 4800 participants was assessed with active surveillance for adverse events. The trial is registered at www.isrctn.com, ISRCTN11643110. 41 344 children were vaccinated in April–May, 2018, with another 20 412 children vaccinated at catch-up vaccination campaigns between September and December, 2018, and April and May, 2019. The incidence of typhoid fever (cases per 100 000 person-years) was 635 in JE vaccinees and 96 in Vi-TT vaccinees (total Vi-TT protection 85%; 97·5% CI 76 to 91, p<0·0001). Total vaccine protection was consistent in different age groups, including children vaccinated at ages under 2 years (81%; 95% CI 39 to 94, p=0·0052). The incidence was 213 among all residents in the JE clusters and 93 in the Vi-TT clusters (overall Vi-TT protection 57%; 97·5% CI 43 to 68, p<0·0001). We did not observe significant indirect vaccine protection by Vi-TT (19%; 95% CI −12 to 41, p=0·20). The vaccines were well tolerated, and no serious adverse events judged to be vaccine-related were observed. Vi-TT provided protection against typhoid fever to children vaccinated between 9 months and less than 16 years. Longer-term follow-up will be needed to assess the duration of protection and the need for booster doses. The study was funded by the Bill & Melinda Gates Foundation.

This randomized trial enrolled 442 infants in the Republic of Korea to assess the immunogenicity and safety of a combined diphtheria, tetanus, acellular pertussis, and inactivated poliovirus vaccine (DTaP–IPV; Tetraxim™) for primary vaccination at 2, 4 and 6 months of age compared with DTaP and IPV vaccines given separately. Immunogenicity was high in both groups; seroprotection and seroconversion rates of the combined vaccine (Group A) were non-inferior to the control vaccines (Group B). All subjects were seroprotected against poliovirus types 1, 2 and 3 (≥81/dil) and anti-diphtheria (≥0.01IU/mL); 99.0% were seroprotected against tetanus (≥0.1IU/mL). At least 93.6% had anti-diphtheria antibody titers ≥0.1IU/mL. Anti-pertussis toxoid (PT) and anti-filamentous haemagglutinin (FHA) seroconversion (≥4-fold increase in antibody titer) rates were 96.6% and 94.4% for Group A, 92.2% and 78.4% for Group B. Most solicited reactions occurred within 4 days of vaccination, resolved within 3 days and were mild. Severe solicited reactions occurred after ≤0.5% of doses in Group A and ≤0.9% in Group B. No withdrawals occurred because of adverse events. The DTaP–IPV combined vaccine given at 2, 4, and 6 months of age was well tolerated; immunogenicity was similar to the control vaccines.

•Phase 1 study of a toxoid A and B vaccine in healthy adults aged 50–85 years.•Immunogenicity was present after Dose 2, with an anamnestic response at Month 7.•Response was higher in the toxoid-only groups than in the Al(OH)3-containing groups.•No clear dose response was evident in either the 50–64-year or 65–85-year cohort.•Magnitude of the immune response was similar in the 2 age cohorts.•Most common local reactions and systemic events were injection site pain, headache and fatigue. Clostridium difficile is a significant cause of morbidity and mortality in hospitals, nursing homes, and long-term care facilities. The bacteria can produce 3 toxins, of which the C. difficile toxin A and C. difficile toxin B are the principal virulence factors for C. difficile-associated disease. A phase 1, first-in-human, placebo-controlled, dose-escalation study was performed to assess the safety and immunogenicity of an investigational vaccine candidate consisting of genetically and chemically detoxified, purified toxins A and B. The toxoids, either alone or in combination with aluminum hydroxide (Al(OH)3), were administered to healthy adults 50–85 years of age at antigen dose levels of 50, 100, or 200μg in a 3-dose regimen administered at 0, 1, and 6 months. Overall, the C. difficile vaccine formulations and doses administered were generally well tolerated. Local reactions and systemic events were predominantly mild to moderate, were more common in the 50–64-year age cohort, and comprised mostly injection site pain, headache, and fatigue. In subjects who received the vaccine formulations, both the toxin A- and toxin B-specific neutralizing antibody geometric mean concentrations increased substantially at 1 month after Dose 2 and after Dose 3 compared to baseline. In the 50–64-year age cohort, geometric mean fold rises (GMFRs) in toxin A-specific neutralizing antibodies from baseline at Month 7 ranged from 59.19 to 149.23 in the vaccine groups compared to 2.47 in the control group. For toxin-B specific neutralizing antibodies, the GMFRs from baseline at Month 7 ranged from 116.67 to 2503.75 in the vaccine groups compared to 2.48 in the control group. In the 65–85-year age cohort, GMFRs in toxin A-specific neutralizing antibodies from baseline at Month 7 ranged from 42.73 to 254.77 in the vaccine groups compared to 2.03 in the control group. For toxin-B specific neutralizing antibodies, the GMFRs from baseline at Month 7 ranged from 136.12 to 4922.80 in the vaccine groups compared to 1.58 in the control group. Potent antitoxin neutralizing responses were still evident in immunized subjects in both age groups at Month 12. Although there was no clear dose-level response pattern, the data suggest that both the antitoxin A- and B-specific neutralizing responses were trending higher in the toxoid-only groups compared to the toxoid+Al(OH)3 groups. Furthermore, the magnitude of the immune response was similar in the 2 age cohorts. The vaccine formulations studied in this phase 1 study were immunogenic and well tolerated. The results presented support further development of the C. difficile vaccine candidate in a larger population of subjects to determine the optimal dose and immunization schedule. NCT01706367.

Postnatal exposure to perfluorinated alkylate substances (PFASs) is associated with lower serum concentrations of specific antibodies against certain childhood vaccines at 7 y. We prospectively followed a Faroese birth cohort to determine these associations at 13 y. In 516 subjects (79% of eligible cohort members) who were 13 years old, serum concentrations of PFASs and of antibodies against diphtheria and tetanus were measured and were compared with data from the previous examination at 7 y. Multiple regression analyses and structural equation models were applied to determine the association between postnatal PFAS exposures and antibody concentrations. Serum concentrations of PFASs and antibodies generally declined from 7 y to 13 y. However, 68 subjects had visited the emergency room and had likely received a vaccination booster, and a total of 202 children showed higher vaccine antibody concentrations at 13 y than at 7 y. Therefore, separate analyses were conducted after exclusion of these two subgroups. Diphtheria antibody concentrations decreased at elevated PFAS concentrations at 13 y and 7 y; the associations were statistically significant for perfluorodecanoate (PFDA) at 7 y and for perfluorooctanoate (PFOA) at 13 y, both suggesting a decrease by ∼25% for each doubling of exposure. Structural equation models showed that a doubling in PFAS exposure at 7 y was associated with losses in diphtheria antibody concentrations at 13 y of 10–30% for the five PFASs. Few associations were observed for anti-tetanus concentrations. These results are in accord with previous findings of PFAS immunotoxicity at current exposure levels. https://doi.org/10.1289/EHP275.

There is a high global incidence of typhoid fever, with an annual mortality rate of 200,000 deaths. Typhoid fever also affects younger children, particularly in resource-limited settings in endemic countries. Typhoid vaccination is an important prevention tool against typhoid fever. However, the available polysaccharide typhoid vaccines are not recommended for children under 2 years of age. A new typhoid conjugate Vi-diphtheria toxoid (Vi-DT) vaccine has been developed for infant immunization. We aimed to define the safety and immunogenicity of the Vi-DT vaccine among adults and children in Indonesia. An observational, blinded, comparative, randomized, phase I safety study in two age de-escalating cohorts was conducted in East Jakarta, Indonesia, from April 2017 to February 2018. We enrolled 100 healthy subjects in 2 age groups: adults and children (18-40 and 2-5 years old). These groups were randomized into study groups (Vi-DT vaccine), and comparator groups (Vi-polysaccharide (Vi-PS) vaccine and another additional vaccine) which was administered in 4 weeks apart. Subjects were followed up to six months. One hundred healthy adults and children subjects completed the study. The Vi-DT and Vi-PS vaccines showed no difference in terms of intensity of any immediate local and systemic events within 30 minutes post-vaccination. Overall, pain was the most common local reaction, and muscle pain was the most common systemic reaction in the first 72 hours. No serious adverse events were deemed related to vaccine administration. The first and second doses of the Vi-DT vaccine induced seroconversion and higher geometric mean titers (GMT) in all subjects compared to that of baseline. However, in terms of GMT, the second dose of Vi-DT did not induce a booster response. The Vi-DT vaccine is safe and immunogenic in adults and children older than two years. A single dose of the vaccine is able to produce seroconversion and high GMT in all individuals.

A clinical trial in patients with glioblastoma shows increased immune and anti-tumour responses to dendritic cell vaccination after pre-conditioning the site of vaccination with tetanus toxoid (Td); similar results are also seen in mice in part due to the actions of the chemokine CCL3, and the findings may represent new ways to improve the efficacy of anti-cancer vaccines. A novel anti-tumour immunotherapy strategy John Sampson and colleagues report on a small clinical trial in glioblastoma patients that shows that the immune and anti-tumour response to dendritic cell vaccination is increased by pre-conditioning the site of vaccination with tetanus/diptheria toxoid (Td). Experiments in mice showed similar effects and demonstrated that pre-conditioning with Td enhanced migration of dendritic cells to the tumours, at least in part due to the action of the cytokine CCL3. Although the clinical trial reported is small, these findings may pave the way for new ways of improving the efficacy of anti-cancer vaccines. After stimulation, dendritic cells (DCs) mature and migrate to draining lymph nodes to induce immune responses 1 . As such, autologous DCs generated ex vivo have been pulsed with tumour antigens and injected back into patients as immunotherapy. While DC vaccines have shown limited promise in the treatment of patients with advanced cancers 2 , 3 , 4 including glioblastoma 5 , 6 , 7 , the factors dictating DC vaccine efficacy remain poorly understood. Here we show that pre-conditioning the vaccine site with a potent recall antigen such as tetanus/diphtheria (Td) toxoid can significantly improve the lymph node homing and efficacy of tumour-antigen-specific DCs. To assess the effect of vaccine site pre-conditioning in humans, we randomized patients with glioblastoma to pre-conditioning with either mature DCs 8 or Td unilaterally before bilateral vaccination with DCs pulsed with Cytomegalovirus phosphoprotein 65 (pp65) RNA. We and other laboratories have shown that pp65 is expressed in more than 90% of glioblastoma specimens but not in surrounding normal brain 9 , 10 , 11 , 12 , providing an unparalleled opportunity to subvert this viral protein as a tumour-specific target. Patients given Td had enhanced DC migration bilaterally and significantly improved survival. In mice, Td pre-conditioning also enhanced bilateral DC migration and suppressed tumour growth in a manner dependent on the chemokine CCL3. Our clinical studies and corroborating investigations in mice suggest that pre-conditioning with a potent recall antigen may represent a viable strategy to improve anti-tumour immunotherapy.

WHO currently recommends a single dose of typhoid conjugate vaccine (TCV) in high-burden countries based on 2-year vaccine efficacy data from large randomised controlled trials. Given the decay of immunogenicity, the protection beyond 2 years is unknown. We therefore extended the follow-up of the TyVAC trial in Bangladesh to assess waning of vaccine protection to 5 years after vaccination. We conducted a cluster randomised controlled trial (TyVAC; ISRCTN11643110) in Dhaka, Bangladesh, between 2018 and 2021. Children aged 9 months to 15 years were invited to receive a single dose of TCV or Japanese encephalitis vaccine between April 15, 2018, and November 16, 2019, based on the randomisation of their clusters of residence. Children who received the Japanese encephalitis vaccine were invited to receive TCV at the final visit between Jan 6, and Aug 31, 2021, according to the protocol. This follow-on study extended the follow-up of the original trial until Aug 14, 2023. The primary endpoint of this study was to compare the incidence of blood culture-confirmed typhoid between children who received TCV in 2018–19 (the previous-TCV group) and those who received the vaccine in 2021 (the recent-TCV group), to evaluate the relative decline in vaccine protection. We also did a nested study using the test-negative design comparing the recent-TCV and previous-TCV groups with unvaccinated individuals, as well as an immunogenicity study in a subset of 1500 children. Compared with the recent-TCV group, the previous-TCV group had an increased risk of typhoid fever between 2021–23, with an adjusted incidence rate ratio of 3·10 (95% CI 1·53 to 6·29; p<0·0001), indicating a decline in the protection of a single-dose of TCV 3–5 years after vaccination. The extrapolated vaccine effectiveness in years 3–5 was 50% (95% CI –13 to 78), and was validated using the test-negative design analysis, with a vaccine effectiveness of 84% (74 to 90) in the recent-TCV group and 55% (36 to 68) in the previous-TCV group, compared with unvaccinated individuals. Anti-Vi-IgG responses declined over the study period. The highest rate of decay was seen in children vaccinated at younger than 2 years in the original trial. The inverse correlation between age and the decay of antibodies was also seen in the subgroup analysis of vaccine effectiveness, where the youngest age group (<7 years at fever visits) exhibited the fastest waning, with vaccine effectiveness dropping to 24% (95% CI –29 to 55) at 3–5 years after vaccination. A decline in the protection conferred by a single-dose TCV was observed 3–5 years after vaccination, with the greatest decline in protection and immune responses observed in children vaccinated at younger ages. A booster dose of TCV around school entry age might be needed for children vaccinated while younger than 2 years to sustain protection against typhoid fever during the school years when the risk is the highest. The Bill & Melinda Gates Foundation.

Vaccine quality control has long relied on animal testing, which involves time, cost, and ethical constraints. This study introduces a ganglioside binding (GB) assay as a complementary in vitro screening tool for tetanus toxoid quality control, which was validated in a single-laboratory environment as a foundational proof-of-concept. The assay reproduces tetanus toxin binding to gangliosides on microplates using simplified procedures. Validation with samples at different inactivation stages showed excellent linearity (0.0002–0.0156 Lf/mL), reproducibility, and a strong correlation with Ramon’s flocculation (R2 = 0.999). The assay clearly distinguished between toxins and toxoids, with the toxoid results remaining at control levels. The time-course inactivation samples were consistent with the animal tests: partially inactivated samples (days 1–3) showed significant GB activity (p < 0.001) and caused 100% mortality, whereas samples from day 4 onward showed no activity and zero mortality. These findings demonstrate that the GB assay reliably differentiates active toxins from toxoids, which aligns with in vivo outcomes. The practical advantages include a simplified protocol, reduced complexity, and improved efficiency for routine testing of samples. As a complementary screening approach, this single-laboratory validation supports the 3Rs principle by demonstrating the potential for reducing animal use while ensuring quality assurance. Broader applicability requires multicenter validation and cross-reactivity, and multicenter validation is ongoing.