Explore the vast range of titles available.

Although measuring vaccine efficacy through the conventional phase III study design, randomized, double-blinded controlled trial serves as the “gold standard”, effectiveness studies, conducted in the context of a public health program, seek to broaden the understanding of the impact of a vaccine in a real world setting including both individual and population level impacts. Cholera is an acute diarrheal infection caused by the ingestion of food or water contaminated with the bacterium Vibrio cholerae. Since the 1980s, either killed or live oral cholera vaccines (OCVs) have been developed and efficacy and effectiveness studies have been conducted on OCV. Although the results of OCV effectiveness studies sometimes showed outliers, the tendency seen is for effectiveness of the vaccine used in public health settings to be somewhat higher than estimated in randomized controlled trials due to the influence of indirect herd protection. Efficacy and Effectiveness studies both generate important information about the vaccine performance characteristics and its impact when used in real world populations at risk for the disease.

Although maintaining vaccines in a strict cold chain has cost and logistical implications in low- and middle-income countries, only a few vaccines have obtained approval for extended controlled temperature conditions (ECTC) application, which permits the administration of vaccines after storage outside of the cold chain for a defined period. We developed a methodology to evaluate stability data and calculate minimum release potency (MRP) in support of ECTC application. The methodology is focused on statistical considerations consisting of stability data collection, statistical analysis plan, statistical modelling, and statistical report. It uses mock stability data from a hypothetical product and may serve as a helpful guide for other products. The statistical data analysis is performed using the R program which is an open-source program and validated using the SAS software. We developed a stability data testing scheme that included 24 lots with six-time points for up to 24 months under real-time and real condition (RT) in the cold chain samples stored at 2–8 °C and 12 lots with six timepoints for 14 days under ECTC samples stored at 40 °C. The log-transformed stability data met the linear regression assumptions and were poolable from representative lots with no significant lot variation. The linear regression analysis model with a common slope and intercept confirmed the stable antigen content over time under RT and ECTC by the mean regression line and 95% confidence interval. Based on the fitted models and the estimated coefficients, the antigen content value of 966 was derived as the MRP under RT for 24 months followed by 14 days under ECTC. The presented framework of statistical considerations, with practical methods and R program codes to perform statistical analysis, may serve as a guide for developing the CTC data for a vaccine’s stability evaluation prospectively.

Typhoid Conjugate Vaccine (TCV) has been shown to elicit robust immune responses among adults and children. However, data on long-term immunogenicity are sparse. The International Vaccine Institute has conducted a Phase I clinical trial in The Philippines to investigate safety and immunogenicity among healthy individual 2–45 years old. In this study we present the results of a long-term immunogenicity study – 5 years after a typhoid conjugate vaccine composed of Vi polysaccharide conjugated to diphtheria toxoid (Vi-DT) and Vi-polysaccharide vaccine was administered. In this observational study, we followed up the participants who were vaccinated by either the Vi-DT vaccine or comparator vaccine, the Vi-polysaccharide vaccine, for five years after the enrollment in the phase I study. We assessed the safety and immunogenicity of the Vi-DT vaccine among healthy Filipino adults and children, aged 2–45 years and compared it descriptively to a Vi polysaccharide vaccine. Participants who had received at least one dose of either vaccine and agreed to provide at least one blood sample were enrolled to the study. Blood samples were collected to assess the longevity of immunity using anti-Vi IgG and serum bactericidal antibody (SBA) at three different time points: 3 years, 4 years, and 5 years after the vaccination. Between 30 October 2019 and 13 January 2022, blood samples were collected from 137 participants who had received at least one dose of Vi-DT or Vi polysaccharide vaccine, 3 years post-vaccination. Anti-Vi IgG seroconversion of Vi-DT vaccinees was higher in all age strata; 98.44 % (95 % confidence interval (CI): 91.67, 99.72) at year 3, 100.00 % (95 % CI: 94.08, 100.00) at year 4 and 98.41 % (95 % CI: 91.54, 99.72) at year 5. Anti-Vi IgG GMT was higher in the Vi-DT group among all age strata as well. Seroconversion by SBA in the Vi-DT group was higher in the 18–45 age group calculating 75.00 % (95 % CI: 50.50, 89.82), 86.67 % (95 % CI: 62.12, 96.26), and 60.00 % (95 % CI: 35.75, 80.18) at 3rd, 4th and 5th year post-vaccination, respectively. The Vi-DT vaccine provides immunity for at least five years after vaccination. However, data beyond 5 years would be valuable to inform the need for booster doses.

Typhoid fever remains a major public health threat to Low- and Middle-Income (LMIC) countries. The typhoid conjugate vaccine (TCV) is a promising vaccine platform to avert the disease as they elicit sufficient immune response in both adults and children. However, data on long-lasting immune response among children below 2 years are very limited. In this article we present the data collected from healthy Filipino children who were administered with Vi-DT vaccine. In this long-term follow-up study, we included children who had been vaccinated with Vi-DT vaccine and received a booster dose either in the short-term (24 weeks) or in the long-term (96 or 110 weeks). 285 participants divided into three cohort stratum, age strata 1 (6 months to less than 9 months), age strata 2 (9 months to 12 months), and age strata 3 (13 months to 23 months) from the phase II clinical trial were tracked and enrolled in the observational study. Blood samples were collected at 3rd, 4th and 5th year after the vaccination and compared descriptively against the comparator. We assessed the long-term immunogenicity using anti-Vi IgG and serum bactericidal antibody (SBA). Between 24 August 2021 to 28 July 2023, 268 healthy Filipino children were enrolled in the study who received at least one dose of Vi-DT or comparator vaccine from the Phase II clinical trial. Anti-Vi IgG seroconversion were higher in Vi-DT vaccine compared to the comparator, calculating 92.79 % (95 % CI: 88.44, 95.58), 88.68 % (83.71, 92.27), and 86.38 % (81.13,90.35) in the Vi-DT group, and 26.92 % (16.77, 40.25), 29.09 % (18.77, 42.14), and 25.45 % (15.81,38.30) in comparator group at 3rd, 4th and 5th year respectively. The seroconversion is higher in the Vi-DT long-term booster group than in short-term booster group in all age strata except age strata 3 at 5th year which is 83.78 % (68.86,92.35) and 88.89 % (74.69, 95.59) in Vi-DT long-term booster and short-term booster group, respectively. The SBA GMT response was observed to be higher in the Vi-DT vaccine group in all age strata compared to the comparator vaccine, calculating 932.06 (694.14, 1251.53), 958.61 (721.84, 1273.05) and 724.38 (537.89, 975.55) in the Vi-DT vaccine group and 657.63 (367.43, 1177.03), 796.27 (454.92, 1393.76), and 611.83 (338.10, 1107,18) in comparator group at 3rd year, 4th year and 5th year respectively. When administered as a long-term booster dose 2 years after the primary single-dose, the Vi-DT vaccine is capable of eliciting a sustained immune response for at least 5 years following vaccination. The result in this study will support the inclusion of Vi-DT vaccine in the routine immunization program in the endemic and semi-endemic areas.