INCLEN Intussusception Surveillance Network Study Group. Risk of intussusception after monovalent rotavirus vaccine (Rotavac) in Indian infants: A self-controlled case series analysis

Tree-temporal scan statistics for safety signal detection in vaccine clinical trials

The evaluation of safety is critical in all clinical trials. However, the quantitative analysis of safety data in clinical trials poses statistical difficulties because of multiple potentially overlapping endpoints. Tree-temporal scan statistic approaches address this issue and have been widely employed in other data sources, but not to date in clinical trials. We evaluated the performance of three complementary scan statistical methods for routine quantitative safety signal detection: the self-controlled tree-temporal scan (SCTTS), a tree-temporal scan based on group comparison (BGTTS), and a log-rank based tree-temporal scan (LgRTTS). Each method was evaluated using data from two phase III clinical trials, and simulated data (simulation study). In the case study, the reference set was adverse events (AEs) in the Reference Safety Information of the evaluated vaccine. The SCTTS method had higher sensitivity than other methods, and after dose 1 detected 80 true positives (TP) with a positive predictive value (PPV) of 60%. The LgRTTS detected 49 TPs with 69% PPV. The BGTTS had 90% of PPV with 38 TPs. In the simulation study, with simulated reference sets of AEs, the SCTTS method had good sensitivity to detect transient effects. The LgRTTS method showed the best performance for the detection of persistent effects, with high sensitivity and expected probability of type I error. These three methods provide complementary approaches to safety signal detection in clinical trials or across clinical development programmes. All three methods formally adjust for multiple testing of large numbers of overlapping endpoints without being excessively conservative.

Geospatial methodology for determining the regional prevalence of hospital-reported childhood intussusception in patients from India

Both developed and developing countries carry a large burden of pediatric intussusception. Sentinel site surveillance-based studies have highlighted the difference in the regional incidence of intussusception. The objectives of this manuscript were to geospatially map the locations of hospital-confirmed childhood intussusception cases reported from sentinel hospitals, identify clustering and dispersion, and reveal the potential causes of the underlying pattern. Geospatial analysis revealed positive clustering patterns, i.e., a Moran's I of 0.071 at a statistically significant (p value < 0.0010) Z score of 16.14 for the intussusception cases across India (cases mapped n = 2221), with 14 hotspots in two states (Kerala = 6 and Tamil Nadu = 8) at the 95% CI. Granular analysis indicated that 67% of the reported cases resided < 50 km from the sentinel hospitals, and the average travel distance to the sentinel hospital from the patient residence was calculated as 47 km (CI 95% min 1 km-max 378 km). Easy access and facility referral preferences were identified as the main causes of the existing clustering pattern of the disease. We recommend designing community-based surveillance studies to improve the understanding of the prevalence and regional epidemiological burden of the disease.

The safety of seasonal influenza vaccination among adults prescribed immune checkpoint inhibitors: A self-controlled case series study using administrative data

BACKGROUND

Immune checkpoint inhibitor (ICI) therapy for patients undergoing cancer treatment carries a risk of severe immune-related adverse events (IRAEs). Questions remain about whether seasonal influenza vaccination might increase the risk of developing IRAEs among these patients given that vaccines are immunomodulatory. Previous vaccine safety studies on patients with cancer prescribed ICI therapy have demonstrated conflicting results.

METHODS

Using health administrative data from Ontario, Canada among adults diagnosed with cancer who had been prescribed ICI therapy and who had received an influenza vaccine from 2012 to 2019, we conducted a self-controlled case series study. The pre-vaccination control period started 42-days post-ICI initiation until 14-days prior to vaccination, the risk period was 1-42 days post-vaccination, and the post-vaccination control period was after the risk period until ICI discontinuation or a maximum period of two years. Emergency department (ED) visit(s) and/or hospitalization for any cause after ICI initiation was used to identify severe IRAEs. We fitted a fixed-effects Poisson regression model accounting for seasonality and calendar time to estimate relative incidence of IRAEs between risk and control periods.

RESULTS

We identified 1133 records of cancer patients who received influenza vaccination while prescribed ICI therapy. Most were aged ≥ 66 years (73 %), were male (63 %), had lung cancer (54 %), and had received ICI therapy with a programmed cell death protein 1(PD-1) inhibitor (91 %). A quarter (26 %) experienced an ED visit and/or hospitalization during the observation period. Rates of ED visits and/or hospitalizations in the risk vs. control periods were similar, with an incidence rate ratio of 1.04 (95 % CI: 0.75-1.45). Subgroup and sensitivity analyses yielded similar results.

CONCLUSION

Seasonal influenza vaccination was not associated with an increased incidence of ED visit or hospitalization among adults with cancer treated with ICI therapy and our results support further evidence of vaccine safety.

Immunogenicity of RV1 and RV5 vaccines administered in standard and interchangeable mixed schedules: a randomized, double-blind, non-inferiority clinical trial in Mexican infants

Introduction

Rotavirus-associated diarrheal diseases significantly burden healthcare systems, particularly affecting infants under five years. Both Rotarix™ (RV1) and RotaTeq™ (RV5) vaccines have been effective but have distinct application schedules and limited interchangeability data. This study aims to provide evidence on the immunogenicity, reactogenicity, and safety of mixed RV1-RV5 schedules compared to their standard counterparts.

Methods

This randomized, double-blind study evaluated the non-inferiority in terms of immunogenicity of mixed rotavirus vaccine schedules compared to standard RV1 and RV5 schedules in a cohort of 1,498 healthy infants aged 6 to 10 weeks. Participants were randomly assigned to one of seven groups receiving various combinations of RV1, and RV5. Standard RV1 and RV5 schedules served as controls of immunogenicity, reactogenicity, and safety analysis. IgA antibody levels were measured from blood samples collected before the first dose and one month after the third dose. Non-inferiority was concluded if the reduction in seroresponse rate in the mixed schemes, compared to the standard highest responding scheme, did not exceed the non-inferiority margin of -0.10. Reactogenicity traits and adverse events were monitored for 30 days after each vaccination and analyzed on the entire cohort.

Results

Out of the initial cohort, 1,365 infants completed the study. Immunogenicity analysis included 1,014 infants, considering IgA antibody titers ≥20 U/mL as seropositive. Mixed vaccine schedules demonstrated non-inferiority to standard schedules, with no significant differences in immunogenic response. Safety profiles were comparable across all groups, with no increased incidence of serious adverse events or intussusception.

Conclusion

The study confirms that mixed rotavirus vaccine schedules are non-inferior to standard RV1 and RV5 regimens in terms of immunogenicity and safety. This finding supports the flexibility of rotavirus vaccination strategies, particularly in contexts of vaccine shortage or logistic constraints. These results contribute to the global effort to optimize rotavirus vaccination programs for broader and more effective pediatric coverage.Clinical trial registration: ClinicalTrials.gov, NCT02193061.

Evaluation of Intussusception Following Pentavalent Rotavirus Vaccine (RotaTeq) Administration in 5 African Countries

BACKGROUND

A low-level risk of intussusception following rotavirus vaccination has been observed in some settings and may vary by vaccine type. We examined the association between RotaTeq vaccination and intussusception in low-income settings in a pooled analysis from 5 African countries that introduced RotaTeq into their national immunization program.

METHODS

Active surveillance was conducted at 20 hospitals to identify intussusception cases. A standard case report form was completed for each enrolled child, and vaccination status was determined by review of the child's vaccination card. The pseudo-likelihood adaptation of self-controlled case-series method was used to assess the association between RotaTeq administration and intussusception in the 1-7, 8-21, and 1-21 day periods after each vaccine dose in infants aged 28-245 days.

RESULTS

Data from 318 infants with confirmed rotavirus vaccination status were analyzed. No clustering of cases occurred in any of the risk windows after any of the vaccine doses. Compared with the background risk of naturally occurring intussusception, no increased risk was observed after dose 1 in the 1-7 day (relative incidence = 2.71; 95% confidence interval [CI] = 0.47-8.03) or the 8-21 day window (relative incidence = 0.77; 95%CI = 0.0-2.69). Similarly, no increased risk of intussusception was observed in any risk window after dose 2 or 3.

CONCLUSIONS

RotaTeq vaccination was not associated with increased risk of intussusception in this analysis from 5 African countries. This finding mirrors results from similar analyses with other rotavirus vaccines in low-income settings and highlights the need for vaccine-specific and setting-specific risk monitoring.

Adverse Events Following Immunization- The Known Unknowns and Black Box : Based on 10th Dr. I. C. Verma Excellence Award for Young Pediatricians Delivered as Oration on 9th Oct. 2022

Although vaccines are one of the most rigorously tested biological products, the safety concerns persist globally. The vaccine safety concerns linked to measles, pentavalent and human papillomavirus (HPV) vaccines have affected the vaccine coverage significantly in past. While surveillance of adverse events following immunization (AEFI) is part of the national immunization program mandate, it suffers from challenges and biases related to reporting, completeness, and quality. Some conditions of concern, termed as adverse events of special interest (AESI) following vaccination, mandated specialised studies to prove/disprove the association. The AEFIs/AESIs are usually caused by one of the four pathophysiologic mechanisms, but for several AEFIs/AESIs, the exact pathophysiology remains elusive. For the causality assessment of AEFIs, a systematic process with checklists and algorithm are followed to classify into one of the four causal association categories. While the causal association primarily banks on epidemiological observations for several AEFIs, the emerging evidences indicate roles of underlying genetic, gender, age and other pro-inflammatory risk factors for AEFIs and AESIs. The emerging evidences suggest role of antigenic mimicry, autoantibody(ies) and underlying genetic susceptibility for the AEFIs/AESIs. The uncertainty about the frequency, profile, interval, and severity of AEFIs/AESIs and variations across the population, ambiguity about the exact pathophysiology mechanism, absence of definite markers, suggest a possible black box effect of the vaccines. Unless these unanswered questions concerning the AEFIs/AESIs are addressed appropriately and communicated to the stakeholders (professionals, care providers, beneficiaries, general public and media), the anti-vaccine movement shall keep challenging the vaccine and vaccination program.

Impact of vaccination with different types of rotavirus vaccines on the incidence of intussusception: a randomized controlled meta-analysis

Background

Intussusception is a prevalent pediatric issue causing acute abdominal pain, with potential links to rotavirus vaccines. The variety of these vaccines has grown in recent years. This meta-analysis study aims to evaluate the impact of various rotavirus vaccines on intussusception incidence.

Methods

We executed a thorough search across databases like PubMed, Cochrane Library, Embase, and Web of Science, leading to the selection of 15 credible randomized controlled trials (RCTs) that encompass various types of rotavirus vaccines. From each study, we extracted essential details such as vaccine types and intussusception occurrences. We assessed the risk of bias using the Cochrane Collaboration's tool, conducted statistical analysis with R (version 4.2.3), determined relative risk (RR) using a random effects model, and performed a subgroup analysis for vaccines of differing brands and types.

Results

We included 15 randomized controlled studies from various countries. While intussusception incidence differed between vaccinated and control groups, this difference was not statistically significant. The overall risk ratio (RR), calculated using a random effects model, was 0.81, with a 95% confidence interval of [0.53, 1.23]. This crossing 1 shows that vaccination didn't notably change disease risk. Additionally, the 0% group heterogeneity suggests consistency across studies, strengthening our conclusions. Subgroup analysis for different vaccine brands and types (RV1 (Rotarix, Rotavac, RV3-BB), RV3 (LLR3), RV5 (RotasiiL, RotaTeq), and RV6) showed no significant variation in intussusception incidence. Despite variations in RR among subgroups, these differences were not statistically significant (P > 0.05).

Conclusions

Our study indicates that rotavirus vaccination does not significantly increase the incidence of intussusception. Despite varying impacts across different vaccine brands and types, these variations are insignificant. Given the substantial benefits outweighing the risks, promoting the use of newly developed rotavirus vaccines remains highly valuable.

Systematic Review Registration

www.crd.york.ac.uk/prospero/, Identifier CRD42023425279.

M. Eljaro Z, Abu-Awwad F, Bozya Y, Hjaija D, Bhat N, Leader T, Ramlawi A, Marzouqa H. Introducing ROTAVAC® to the occupied Palestinian Territories: Impact on diarrhea incidence, rotavirus prevalence and genotype composition

BACKGROUND

Rotavirus infection remains an important cause of morbidity and mortality in children. The introduction of vaccination programs in more than 100 countries has contributed to a decrease in hospitalizations and mortality. This study investigates the epidemiological impact of the rotavirus vaccine ROTAVAC® in the Palestinian Territories, the first country to switch from ROTARIX® to this new vaccine.

METHODS

Clinical surveillance data was collected fromchildren younger than 5attendingoutpatient clinics throughout Gaza withdiarrhea between 2015 and 2020. The incidence of all-cause diarrhea was assessed using an interrupted time-series approach. Rotavirus prevalence was determined at the Caritas Baby Hospital in the West Bank usingELISA on stool specimen of children younger than 5with diarrhea. Genotyping was performed on 325 randomly selected rotavirus-positive samples from January 2015 through December 2020 using multiplex PCR analysis.

RESULTS

Average monthly diarrhea casesdropped by 16.7% annually fromintroduction of rotavirus vaccination in May 2016 to the beginning of the SARS-CoV-2 epidemic in March 2020 for a total of 53%. Case count declines were maintained afterthe switchto ROTAVAC® in October 2018. Rotavirus positivity in stool samples declined by 67.1% over the same period without change followingthe switch to ROTAVAC®. The distribution of predominant genotypes in rotavirus-positive stool samples changed from a pre-vaccination G1P [8] to G9P[8] and G12P[8] during the ROTARIX® period and G2P[4] after the introduction of ROTAVAC®.

CONCLUSION

ROTAVAC® has shown epidemiological impact on par with ROTARIX® after its introduction to the national immunization schedule in the Palestinian Territories. A molecular genotype shift from a pre-vaccination predominance of G1P[8] to a current predominance of G2P[4] requires more long-term surveillance.

Rotavirus vaccines: progress and new developments

INTRODUCTION

Rotavirus is the primary cause of severe acute gastroenteritis among children under the age of five globally, leading to 128,500 to 215,000 vaccine-preventable deaths annually. There are six licensed oral, live-attenuated rotavirus vaccines: four vaccines pre-qualified for global use by WHO, and two country-specific vaccines. Expansion of rotavirus vaccines into national immunization programs worldwide has led to a 59% decrease in rotavirus hospitalizations and 36% decrease in diarrhea deaths due to rotavirus in vaccine-introducing countries.

AREAS COVERED

This review describes the current rotavirus vaccines in use, global coverage, vaccine efficacy from clinical trials, and vaccine effectiveness and impact from post-licensure evaluations. Vaccine safety, particularly as it relates to the risk of intussusception, is also summarized. Additionally, an overview of candidate vaccines in the pipeline is provided.

EXPERT OPINION

Considerable evidence over the past decade has demonstrated high effectiveness (80-90%) of rotavirus vaccines at preventing severe rotavirus disease in high-income countries, although the effectiveness has been lower (40-70%) in low-to-middle-income countries. Surveillance and research should continue to explore modifiable factors that influence vaccine effectiveness, strengthen data to better evaluate newer rotavirus vaccines, and aid in the development of future vaccines that can overcome the limitations of current vaccines.

Self-controlled case series design in vaccine safety: a systematic review

BACKGROUND

: An increasing number of vaccine safety studies using the self-controlled case-series (SCCS) design have been conducted in the last decade. However, there has been no comprehensive evaluation of the methodology and reporting quality of these observational studies. The purpose of this paper is to document the methodological features of studies that focused on vaccine safety using the SCCS design, and to evaluate the reporting quality of these studies to suggest future improvements on appropriate design and transparent reporting.

METHODS

: Databases including Medline, Embase, Web of Science, Scopus and Chinese databases were searched from inception to May 31, 2021. All observational studies regarding vaccine safety using a SCCS design were selected. Information regarding methodological elements were extracted. In addition, reporting quality was assessed using the REporting of studies Conducted using Observational Routinely collected health Data statement for PharmacoEpidemiology (RECORD-PE).

RESULTS

: Of the 105 studies identified, administrative databases were the main data source for vaccination records and adverse events following immunization (AEFI). 28 articles (27%) used multiple designs to verify the association, and the results obtained with the SCCS design were robust. The top three AEFI studied were intussusception, Guillain-Barré syndrome, and convulsions. Only 21 studies (20%) reported the approach for case validation by chart review. The healthy vaccinee effect was considered by 51studies (49%), with 16 of them (31%) using extended SCCS models to alleviate this effect. Overall, the reporting quality of included studies could be improved.

CONCLUSIONS

: This study systematically reviewed the methodology of studies regarding vaccine safety using a SCCS design and critically assessed their respective reporting quality. Case validation, the validity of assumptions for standard SCCS, and quality of reporting should be given more importance in future research projects.

Vaccination of pregnant rhesus monkeys with inactivated rotavirus as a model for achieving protection from rotavirus SA11 infection in the offspring

Live-attenuated rotavirus vaccine has shown low protection in underdeveloped or developing countries. However, the inactivated rotavirus vaccine may have the potential to overcome some of these challenges. In the present study, the immunogenicity and protective efficacy of a bivalent inactivated rotavirus vaccine by parenteral administration were elevated in a neonatal rhesus monkey model. A bivalent inactivated rotavirus vaccine containing G1P[8] (ZTR-68 strain) and G9P[8] (ZTR-18 strain) was administered to pregnant rhesus monkeys twice at an interval of 14 days. Neutralizing antibodies against RV strains ZTR-68, ZTR-18, SA11, WA, UK, and Gottfried emerged in pregnant rhesus monkeys and were transplacentally transmitted to the offspring. In the vaccine group, clinical symptoms of diarrhea, viral load in the gut tissue and histopathological changes were significantly reduced in the neonatal rhesus monkeys following oral challenge with the SA11 strain.

Epidemiology of intussusception in sub-Saharan Africa

This supplement contains the findings from intussusception surveillance conducted in 9 countries. These articles provide information on the age distribution of intussusception in the first year of life with cases peaking at 4-6 months of age, highlight the high proportion of cases in most, but not all, countries that undergo surgery and often require bowel resection for the treatment of intussusception, and show the variability of treatment outcomes in different countries. These data will be important for improving diagnosis and treatment of intussusception in young children in sub-Saharan Africa.

Global Experience with Rotavirus Vaccines

Rotavirus is a major cause of severe pediatric diarrhea worldwide. In 2006, two live, oral rotavirus vaccines, Rotarix and RotaTeq, were licensed for use in infants and were rapidly adopted in many high- and middle-income settings where efficacy had been demonstrated in clinical trials. Following completion of additional successful trials in low-income settings, the World Health Organization (WHO) recommended rotavirus vaccination for all infants globally in 2009. In 2018, two new rotavirus vaccines, Rotasiil and Rotavac, were prequalified by WHO, further expanding global availability. As of March 2021, rotavirus vaccines have been introduced nationally in 106 countries. Since introduction, rotavirus vaccines have demonstrated effectiveness against severe disease and mortality, even among age groups not eligible for vaccination. Cross-genotypic protection has also been demonstrated, and the favorable benefit-risk profile of these vaccines continues to be confirmed via post-marketing surveillance. Ongoing research seeks to better understand reasons for the lower effectiveness observed in lower-resource settings, and to use these findings to optimize vaccine strategies worldwide.

Estimating Relative Risk When Observing Zero Events-Frequentist Inference and Bayesian Credibility Intervals

Relative risk (RR) is a preferred measure for investigating associations in clinical and epidemiological studies with dichotomous outcomes. However, if the outcome of interest is rare, it frequently occurs that no events are observed in one of the comparison groups. In this case, many of the standard methods used to obtain confidence intervals (CIs) for the RRs are not feasible, even in studies with strong statistical evidence of an association. Different strategies for solving this challenge have been suggested in the literature. This paper, which uses both mathematical arguments and statistical simulations, aims to present, compare, and discuss the different statistical approaches to obtain CIs for RRs in the case of no events in one of the comparison groups. Moreover, we compare these frequentist methods with Bayesian approaches to determine credibility intervals (CrIs) for the RRs. Our results indicate that most of the suggested approaches can be used to obtain CIs (or CrIs) for RRs in the case of no events, although one-sided intervals obtained by methods based on deliberate, probabilistic considerations should be preferred over ad hoc methods. In addition, we demonstrate that Bayesian approaches can be used to obtain CrIs in these situations. Thus, it is possible to obtain statistical inference for the RR, even in studies with no events in one of the comparison groups, and CIs for the RRs should always be provided. However, it is important to note that the obtained intervals are sensitive to the method chosen in the case of small sample sizes.