Polysaccharide Diphtheria Toxoid Conjugate Research Articles

Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

Towards a marketplace for Vi polysaccharide-conjugate typhoid vaccines

In The Lancet Infectious Diseases, Ganesh Kumar Rai and colleagues 1 Rai GK Saluja T Chaudhary S et al. Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial. Lancet Infect Dis. 2021; (published online Dec 20.)https://doi.org/10.1016/S1473-3099(21)00455-2 PubMed Google Scholar describe the safety and immunogenicity of a new Vi polysaccharide-diphtheria toxoid (Vi-DT) conjugate vaccine, potentially offering a valuable new tool in the global effort to control typhoid fever. The most recent estimates suggest that Salmonella enterica serovar Typhi (S Typhi) was responsible for approximately 10 million cases of typhoid fever and the loss of 9·8 million disability-adjusted life-years in 2017. 2 Stanaway JD Reiner RC Blacker BF et al. The global burden of typhoid and paratyphoid fevers: a systematic analysis for the Global Burden of Disease Study 2017. Lancet Infect Dis. 2019; 19: 369-381 Summary Full Text Full Text PDF PubMed Scopus (210) Google Scholar The highest burden of disease is thought to occur in infants and school-age children (ie, those aged 1–14 years), predominantly in south Asia. Effective long-term disease control will require substantial improvements in water quality and sanitation infrastructure, combined with targeted vaccination campaigns. Even though typhoid vaccines have been used for over a century, the past decade has seen substantial progress in the development of safe and effective vaccines against typhoid fever. Although effective, early generation vaccines have limitations that have precluded their widespread programmatic deployment in routine immunisation schedules. Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trialWhen administered as a single dose, the Vi-DT test vaccine was safe, immunogenic, and non-inferior to the Vi-TT vaccine at 4 weeks post vaccination. Equivalent immunogenicity of the three lots of Vi-DT vaccine was also shown, supporting the manufacturing process of this vaccine. Once prequalified by WHO, this vaccine could be an option for purchase by UN agencies. Full-Text PDF Open Access

Quantification of residual EDU ( N-ethyl- N′-(dimethylaminopropyl) carbodiimide (EDC) hydrolyzed urea derivative) and other residual by LC–MS/MS

An LC–MS/MS method for determination of the break down product of N-ethyl- N′-(3-dimethylaminopropyl) carbodiimide (EDC) urea derivative, EDU, has been developed and validated for monitoring the residual coupling reagents. Results indicate that the method exhibits suitable specificity, sensitivity, precision, linearity and accuracy for quantification of residual EDU in the presence of meningococcal polysaccharide-diphtheria toxoid conjugate vaccine and other vaccine matrix compounds. The assay has been validated for a detection range of 10–100 ng/mL and then successfully transferred to quality control (QC) lab. This same method has also been applied to the determination of residual diaminohexane (DAH) in the presence of EDU. LC–MS/MS has proven to be useful as a quick and sensitive approach for simultaneous determination of multiple residual compounds in glycoconjugate vaccine samples.

Prior meningococcal A/C polysaccharide vaccine does not reduce immune responses to conjugate vaccine in young adults

The immune responses induced in young adults by a meningococcal A/C polysaccharide-diphtheria toxoid conjugate vaccine (Mcj) and a meningococcal A/C plain polysaccharide vaccine (Mps) were evaluated in unvaccinated subjects and those who had received either vaccine previously. 195 subjects aged 17–30 years received either Mps or Mcj. After 12 months, they were randomised again to receive a second dose of either vaccine. Serogroup specific serum bactericidal assay (SBA) titers and IgG antibody responses were assayed before and 4–8 weeks after primary and booster immunisation. Both vaccines were immunogenic in previously unvaccinated subjects. Administration of a dose of Mps after previous Mps or Mcj induced lower bactericidal titers to group C Neisseria meningitidis than those seen after a single dose of Mps. Bactericidal antibody responses to Mcj were not reduced in subjects who had previously received Mps.

Adjuvant activity of QS-21 for experimental E. coli 018 polysaccharide vaccines

Three types of experimental vaccines containing O-side-chain polysaccharide from the enterotoxigenic strain Escherichia coli 018 were evaluated. The immunogenicity of free O-polysaccharide (PS), a polysaccharide-diphtheria toxoid conjugate (PS-conj), and detoxified lipopolysaccharide (dLPS) was tested in female ICR mice, either alone or in combination with QS-21, a purified saponin adjuvant derived from the bark of the tree Quillaja saponaria Molina. Both the number of individual mice responding and the titres of O-polysaccharide specific antibodies in pools of sera were increased by the addition of QS-21. The immune response to both O-specific polysaccharide and carrier was primarily IgM and IgG1. The addition of QS-21 not only increased the level of IgG1, but also had a significant adjuvant effect on antigen-specific IgG2a, IgG2b and IgG3.

Clinical Comparison of the Haemophilus influenzae Type B Polysaccharide-Diphtheria Toxoid and the Oligosaccharide–CRM197 Protein Vaccines in Infancy

To compare two Haemophilus influenzae type B (HiB) conjugate vaccines, a polysaccharide-diphtheria toxoid conjugate (PRP-D) vaccine and an oligosaccharide-CRM197 protein conjugate (HBOC [PRP-CRM]) vaccine, in the same population. One hundred twenty-five thousand infants were randomized to receive the PRP-D or HBOC vaccine. Primary immunization consisted of two doses of either vaccine administered at 4 and 6 months and a booster dose was given at 14 to 18 months. Protection was assessed by recording episodes of invasive disease with HiB isolated from the blood or another normally sterile body site. One thousand thirty-six child health care centers in Finland. Infants born in Finland during the 24-month period from 1987 to 1989. Each vaccine dose was injected intramuscularly in a volume of 0.5 mL. At the same time, a separate site was injected with the diphtheria and tetanus toxoids and pertussis vaccine at 4 months of age, with inactivated poliovirus vaccine at 6 months of age, and with measles-mumps-rubella vaccine at 14 to 18 months of age. The mean anticapsular antibody concentration 1 month after the second dose was 0.63 micrograms/mL and 4.32 micrograms/mL in the PRP-D and HBOC vaccine recipients, respectively. The booster dose resulted in a high antibody concentration: 33.3 micrograms/mL and 58.3 micrograms/mL for PRP-D and HBOC vaccine recipients, respectively. At 36 months of age, the antibody concentration declined to 2.5 micrograms/mL and 5.6 micrograms/mL for PRP-D and HBOC vaccine recipients, respectively. After two doses of the vaccine, there were five episodes (39 were expected based on historical controls) of invasive HiB disease in the PRP-D group and two episodes (35 were expected) in the HBOC group. Hence, an 87% (95% confidence limit [CL], 69, 96) protection rate in the PRP-D group and a 95% (95% CL, 76, 99) protection rate in the HBOC group were achieved. No episodes occurred after the booster dose in either group. Both the PRP-D and HBOC vaccines are safe and effective. A two-dose primary vaccination schedule seems appropriate, at least in circumstances prevailing in Finland and probably in other areas with similar epidemiological effects of HiB disease.

Eradication of Haemophilus influenzae Type b Disease in Southern California

To assess the effects of Haemophilus influenzae vaccination of infants. We evaluated H influenzae type b (Hib) disease rates in Los Angeles County, California (population, 9 million; 1983 through 1992), and in the Southern California Kaiser Health Plan (2.5 million enrollees; 1988 through 1992) during the past decade. Cases were obtained through active and passive disease surveillance in the two populations. The following vaccines were used during the study period (1983 through 1992): (1) Hib polysaccharide vaccine (polyribosyl ribitol phosphate) (used from 1985 through 1987 for children 24 through 60 months of age); (2) Hib polysaccharide-diphtheria toxoid conjugate, Hib polysaccharide CRM197 mutant diphtheria toxoid conjugate vaccine, and Hib polysaccharide outer-membrane protein of group B meningococcus conjugate vaccine in older children (1988 through 1990; ages 15 through 60 months); and (3) Hib polysaccharide CRM197 mutant diphtheria toxoid conjugate vaccine and Hib polysaccharide outer-membrane protein of group B meningococcus conjugate vaccine used in infants (1991 through 1992). Between 1983 and 1988, the Hib disease incidence in Los Angeles County was unchanged (32.7 to 42.5/100,000 person-years in children younger than 5 years). In 1989 through 1990, before Hib conjugate licensure for infant use, Hib disease rates in all age groups declined. After licensure of Hib vaccines for infants in 1990, there was a further fivefold decrease in infants. More dramatic decreases occurred in the better-immunized Kaiser Health Plan children aged 0 through 60 months (53 cases in 1989, only two cases in 1992). The Hib disease has been nearly eradicated in a fully immunized population (Kaiser Health Plan), and significant reductions have also occurred in Los Angeles County.

Immunogenicity of Haemophilus influenzae Type b Conjugate Vaccine in Children with Congenital Asplenia

The immunogenicity of Haemophilus influenzae type b polysaccharide-protein conjugate vaccines in congenitally asplenic children is unknown. The short-term immunogenicity of the H. influenzae type b polysaccharide-diphtheria toxoid conjugate vaccine was therefore assessed in 10 children with congenital asplenia by measuring antipolyribosyl-ribitol phosphate antibody titers. An excellent antibody response was seen in 9 children (mean geometric titer in responders after immunization 44.7 micrograms/mL; range, 2.59-402). The remaining child responded to a booster dose. Further studies are required to assess whether H. influenzae type b conjugate vaccines are immunogenic in infancy in the presence of congenital asplenia.

Rapid disappearance of Haemophilus influenzae type b meningitis after routine childhood immunisation with conjugate vaccines

Mortality from meningitis caused by Haemophilus influenzae type b (Hib), a disease that affects mainly infants and young children, can reach 5% in industrialised countries and ten times that in non-industrialised countries. To determine the efficacy of vaccination against Hib, we carried out a retrospective survey of the incidence of Hib meningitis over five decades in the Greater Helsinki area of Finland, where all children with bacterial meningitis are treated in one of three centres. Except for a meningococcal epidemic in the early 1970s, Hib was the leading cause of childhood bacterial meningitis until the Hib conjugate vaccines changed the picture profoundly. In 1986-87 the polysaccharide-diphtheria toxoid conjugate (PRP-D) was given experimentally to 50% of infants. In 1988-89 all infants were vaccinated, 50% with PRP-D, 50% with another conjugate vaccine, the oligosaccharide-CRM 197 protein conjugate (HbOC). Since 1990 a third conjugate vaccine, the polysaccharide-tetanus toxoid (PRP-T), has been administered routinely to all infants. The vaccines were administered at age 3-6 months, with a booster dose at 14-18 months. In the first 5 years of the Hib vaccination programme the number of cases of Hib meningitis in children aged 0-4 years fell sharply, from 30 in 1986 (the first year of the programme) to none in 1991. The decline contrasts sharply with the rising trend up to the mid 1980s. Vaccination seems to be the only explanation for the observed change in the epidemiology of Hib meningitis.

Efficacy of Haemophilus influenzae type b polysaccharide-diphtheria toxoid conjugate vaccine in US children aged 18-59 months

Vaccines prepared from the polyribosylribitol phosphate (PRP) capsule of Haemophilus influenzae b (Hib) have not consistently shown good efficacy in protecting children aged over 18 months from invasive Hib disease. To evaluate the efficacy of conjugate-PRP vaccines in this age-group, and to compare their effect with that of PRP vaccines, a post-marketing case-control study was conducted among 10 400 000 persons. Between Oct 1,1988, and Feb 28, 1990, 75 patients with Hib disease and 161 control children between 18 and 60 months of age were enrolled. To minimise potentially confounding socioeconomic variables, controls were selected either from among patients' classmates at their day-care centre or from among family acquaintances. 9 of the 75 patients had received the diphtheria toxoid conjugate Hib vaccine more than 2 weeks before onset of illness. After adjusting for age and household crowding, the efficacy of PRP Hib vaccine was 64% (95% Cl = -20, 89) and efficacy of the diphtheria toxoid conjugate Hib vaccine was 74% (95% Cl = 30, 90). The study shows that the protective efficacy of this conjugate vaccine is less than ideal and highlights the need for additional post-licensing studies to confirm and expand understanding of the efficacy of these new products.

A Randomized, Prospective Field Trial of a Conjugate Vaccine in the Protection of Infants and Young Children against InvasiveHaemophilus influenzaeType b Disease

Haemophilus influenzae type b is the leading cause of invasive bacterial disease in young children. The capsular polysaccharide vaccine does not protect children at greatest risk (those under the age of 18 months), but a polysaccharide-protein conjugate vaccine has proved to be more immunogenic in this age group. We enrolled 114,000 infants in Finland in an open, prospective, randomized trial of a H. influenzae type b capsular polysaccharide-diphtheria toxoid conjugate vaccine (polyribosylribitol phosphate-diphtheria toxoid [PRP-D]). Children born on odd-numbered days were vaccinated at the ages of 3, 4, 6, and 14 to 18 months; those born on even-numbered days formed the control group and received the same vaccine at the age of 24 months. After three doses of the vaccine there were 4 cases of verified bacteremic H. influenzae type b disease in the group receiving early vaccination, as compared with 64 cases in the control group, between the ages of approximately 7 and 24 months. The protective efficacy of the vaccine was thus 94 percent (95 percent confidence interval, 83 to 98). No serious adverse effects were reported. The immune response to the conjugate vaccine was characteristic of a T-cell-dependent response when studied in a cohort of 120 infants. The primary immunization series resulted in a geometric mean concentration of anticapsular antibody of 0.53 micrograms per milliliter at the age of seven months, and the fourth dose evoked an anamnestic response, with a mean antibody concentration of 45.22 micrograms per milliliter. A new conjugate vaccine consisting of the capsular polysaccharide of H. influenzae type b covalently linked to a protein carrier (PRP-D), administered to infants beginning at the age of 3 months, is highly effective in protecting young Finnish children (7 to 24 months old) against invasive H. influenzae type b infections.

Disease Caused by Haemophilus influenzae Type b in the Immediate Period After Homologous Immunization: Immunologic Investigation

Several Haemophilus influenzae type b vaccines have been licensed and recommended for administration to children in the United States. These vaccines have consisted of purified polyribosylribitol-phosphate (PRP), the capsular polysaccharide of H influenzae type b, alone or covalently bound to one of several carrier proteins. Two of these saccharide-protein conjugate vaccines are now licensed, a polysaccharide-diphtheria toxoid conjugate (PRP-D) and an oligosaccharide-mutant diphtheria toxin conjugate (HbOC). Two others, a polysaccharide-Neisseria meningitidis outer membrane protein conjugate (PRP-OMPC) and a polysaccharide-tetanus toxoid conjugate (PRP-T), are currently in clinical trials. One concern with the use of PRP vaccine was the suggestion that the incidence of invasive disease caused by H influenzae type b in the immediate period after immunization might be increased; this idea was supported by evidence from several sources. In a case-control study of the efficacy of PRP vaccine, Black et al found that 4 children were hospitalized for invasive disease within 1 week of immunization, a rate of invasive disease 6.4 times greater (95% confidence interval [CI], 2.1 to 19.2) than the background rate in unvaccinated children. In Minnesota, the relative risk for invasive disease in the first week after immunization was 6.2 (95% CI, 0.6 to 45.9), and the results of a study conducted by the Centers for Disease Control in six areas of the United States revealed a 1.8-fold (95% CI, 0.3 to 10.2) increase in the occurrence of invasive disease caused by H influenzae type b in the first week after immunization.(ABSTRACT TRUNCATED AT 250 WORDS)

Cost-benefit analysis of Haemophilus influenzae type b prevention

A cost-benefit analysis of Haemophilus influenzae type b disease preventive strategies was updated to consider evaluation of the H. influenzae type b polysaccharide-diphtheria toxoid conjugate vaccine (PRP-D) and H. influenzae type b oligosaccharide-mutant diphtheria toxin conjugate vaccine (HbOC) for children at 18 months of age. The analysis was done from the perspective of society as a whole. The economic costs of H. influenzae type b disease in the 1988 United States birth cohort would be $2.546 billion (1988 U.S. dollars) in the absence of preventive efforts. If 60% of all children could be vaccinated with PRP-D or HbOC at 18 months of age, this strategy would save $207.1 million ($88.22 savings/vaccinee; $43,605 cost/case prevented; 3.57/1 benefit-to-cost ratio) under base case model assumptions. Universal PRP-D or HbOC vaccination at 18 months of age would prevent 1845 cases of invasive H. influenzae type b disease. The break-even efficacy for universal PRP-D or HbOC vaccination at 18 months of age was 22.7%. We conclude that, under the model base case assumptions, universal PRP-D or HbOC vaccination at 18 months of age is sufficiently efficacious so that the costs of vaccination would be more than offset by decreased medical care costs for treating H. influenzae type b disease.

Simultaneous administration of Haemophilus influenzae type b capsular polysaccharide-diphtheria toxoid conjugate vaccine with routine diphtheria-tetanus-pertussis and inactivated poliovirus vaccinations of childhood

A Haemophilus influenzae type b capsular polysaccharide-diphtheria toxoid conjugate vaccine (PRP-D) is capable of protecting infants against invasive H. influenzae diseases. Therefore it is very likely that it will be incorporated in routine vaccination schedules during the next few years. In order to test the suitability of simultaneous administration of PRP-D and other vaccines we administered it to 25 infants mixed with diphtheria-tetanus-pertussis vaccine at 3, 4 and 6 months and simultaneously, but in a separate syringe, with inactivated polio vaccine at 12 months. A comparison group of equal size received only diphtheria-tetanus-pertussis and inactivated poliovirus vaccines. The concentration of postvaccination antibodies to diphtheria toxoid was 0.411 IU/ml in the group that received PRP-D vs. 0.352 IU/ml in the comparison group, to tetanus toxoid 3.666 vs. 3.668 IU/ml and the neutralization titer to poliovirus type 1 was 370 vs. 320 units in the comparison group, to type 2 titer values were 230 vs. 270 units and to type 3, respectively, 210 vs. 290 units. Thus the seroresponse to antigens in routine vaccines was not affected by the presence of PRP-D in the vaccination schedule, and PRP-D can safely and effectively be included in the vaccination schedule of infancy.

Safety and immunogenicity of Haemophilus influenzae type b polysaccharide and polysaccharide diphtheria toxoid conjugate vaccines in children 15 to 24 months of age

To evaluate the safety and immunogenicity of the Haemophilus influenzae type b polysaccharide vaccine, PRP, and a new polysaccharide-diphtheria toxoid conjugate vaccine, PRP-D, a collaborative study was carried out in six centers in five states. Subjects were 585 infants 15 to 24 months of age. They were randomly assigned to receive a single dose of PRP or PRP-D vaccine. There were no significant differences in the rate of adverse reactions between the two vaccine groups. Minor local reactions occurred in 10.3% of PRP and 12.5% of PRP-D recipients, and fever in 27.4% of PRP and 23.8% of PRP-D recipients. All reactions resolved within 48 hours. Serum samples were obtained just before vaccination and after 1 month. Prevaccination antibody levels were similar for the PRP (0.035 micrograms/mL) and PRP-D (0.027 micrograms/mL) groups, with no differences in levels by age, sex, race, vaccine lot, or study site. Both groups had significant rises in geometric mean levels, but this difference was significantly greater for PRP-D (2.166 micrograms/mL) than for PRP (0.154 micrograms/mL). In addition, the percentage of responders as determined by three definitions (twofold titer rise, greater than 0.15 micrograms/mL, and greater than 1.0 micrograms/mL) was also significantly greater for PRP-D than PRP. In contrast to a marked age-related immunogenicity to PRP (P less than 0.001), there was no significant variation in immune response to PRP-D by age. PRP-D conjugate vaccine appears to be as safe and significantly more immunogenic than PRP vaccine for children vaccinated at 15 to 24 months of age.

Safety and immunogenicity of haemophilus influenzae type b-polysaccharide diphtheria toxoid conjugate vaccine in infants 9 to 15 months of age

Sixty 9- to 15-month-old infants were randomly assigned to receive two doses, 1 month apart, of a Haemophilus influenzae type b capsular polysaccharide-diphtheria toxoid conjugate vaccine (PRP-D) or PRP vaccine, each containing 20 micrograms PRP. There were no significant local or systemic reactions. After one dose of PRP-D, 93% of the subjects attained levels of greater than or equal to 0.15 microgram/ml and 59% achieved greater than or equal to 1 microgram/ml antibody protein. These percentages rose to 100% and 86%, respectively, after the second dose, at which time the geometric mean titer of anti-PRP antibody was 4.8 micrograms/ml. IgG anti-PRP levels were 4.3 times higher than IgM. The proportion of IgG to IgM antibody induced by PRP-D increased with age. After two doses, 33% of the PRP recipients responded with a level of greater than or equal to 0.15 microgram/ml and only 19% responded to a level of greater than or equal to 1.0 microgram/ml. One year later, all of the PRP-D recipients tested still had greater than or equal to 0.15 microgram/ml and more than half had greater than or equal to 1.0 microgram/ml antibody protein.

Safety and Immunogenicity of Haemophilus influenzae Type B Polysaccharide-Diphtheria Toxoid Conjugate Vaccine in Adults

Sixty-one adults received either Haemophilus influenzae type b capsular polyribosephosphate (PRP) vaccine or H. influenzae type b polysaccharide-diphtheria toxoid conjugate (PRP-D) vaccine in two doses, one month apart. Both vaccines were well tolerated with no fever or systemic reactions. There were no significant local reactions. Mild local tenderness was reported by about half of the subjects in both groups. There was no observed effect of the vaccines on hematologic parameters, including reticulocyte and platelet counts, evaluated before immunization, one month after the first dose, and seven to 10 days after the second dose. A single dose of PRP-D induced levels of IgG antibody to PRP three times that observed with PRP alone one month after the first inoculation.