Implementation of accelerated research: strategies for implementation as applied in a phase 1 Ad26.ZEBOV, MVA-BN-Filo two-dose Ebola vaccine clinical trial in Uganda

Gaps in vaccine clinical trials in Africa: A mixed scoping review and bibliometric analysis before, during, and post- COVID-19 pandemic

Africa's participation in vaccine trials has historically been limited, but the COVID-19 pandemic highlighted the need for greater involvement. This study explores vaccine clinical development in Africa, emphasizing its importance for global health security. Using a scoping review and bibliometric analysis, we examined 662 vaccine trials conducted before, during, and after the pandemic. The analysis revealed a significant increase in vaccine trials after 2018 and particularly following the end of the COVID-19 pandemic in May 2023. Most trials focused on viral infections and were single-country studies. Pharmaceutical company sponsors funded most of the earlier trials, with increased government and academic involvement post-2020. Despite progress, challenges remain in the geographic distribution of trials, the number of government-supported studies, and the diversity of conditions studied. Addressing these gaps is crucial to bolstering Africa's role in global vaccine development.

TianTan vaccinia virus-based EBV vaccines targeting both latent and lytic antigens elicits potent immunity against lethal EBV challenge in humanized mice

Epstein-Barr virus (EBV) infection has been related to multiple epithelial cancers and lymphomas. Current efforts in developing a prophylactic EBV vaccine have focused on inducing neutralizing antibodies. However, given the lifelong and persistent nature of EBV infection following primary infection, it is rationalized that an ideal vaccine should elicit both humoral and cellular immune responses targeting multiple stages of the EBV lifecycle. This study used a DNA vector and a TianTan vaccinia virus to express key EBV antigens, including BZLF1, EBNA1, EBNA3B, and gH/gL, to generate multi-antigen vaccines. The multi-antigen vaccine expressing all four antigens and the multi-antigen vaccine expressing BZLF1, EBNA1, and EBNA3B showed comparable protection effects and prevented 100% and 80% of humanized mice, respectively, from EBV-induced fatal B cell lymphoma by activating BZLF1, EBNA1, and EBNA3B specific T cell. The vaccine expressing lytic protein BZLF1 elicited stronger T cell responses and conferred superior protection compared to vaccines targeting single latent EBNA1 or EBNA3B. The vaccine solely expressing gH/gL exhibited no T cell protective effects in our humanized mice model. Our study implicates the potential of EBV vaccines that induce potent cellular responses targeting both latent and lytic phases of the EBV life cycle in the prevention of EBV-induced B cell lymphoma.

Impact of recruitment strategies on individual participation practices in the Canadian National Vaccine Safety Network: prospective cohort study

Background

The Canadian National Vaccine Safety (CANVAS) network conducted a multi-center, prospective vaccine safety study to collect safety data after dose 1 and 2 of COVID-19 vaccines and follow up safety information 7 months after dose 1.

Objective

This study aimed to describe and evaluate the recruitment methods used by CANVAS and the retention of participants by each modality.

Methods

CANVAS deployed a multi-pronged recruitment approach to reach a larger sample, without in-person recruitment. Three primary recruitment strategies were used: passive recruitment, technology-assisted electronic invitation through the vaccine booking system (auto-invitation), or auto-registration through the vaccine registries (auto-enrollment).

Results

Between December 2020 and April 2022, approximately 1.3 million vaccinated adults either self-enrolled or were auto-enrolled in CANVAS, representing about 5% of the vaccinated adult Canadian population. Approximately 1 million participants were auto-enrolled, 300,000 were recruited by auto-invitation, and 5,000 via passive recruitment. Overall survey completion rates for dose 1, dose 2 and the 7-month follow-up surveys were 51.7% (681,198 of 1,318,838), 54.3% (369,552 of 681,198), and 66.4% (452,076 of 681,198), respectively. Completion rates were lower among auto-enrolled participants compared to passively recruited or auto-invited participants who self-enrolled. However, auto-enrolled samples were much larger, which offset the lower completion rates.

Conclusion

Our data suggest that auto-enrollment provided an opportunity to reach and retain a larger number of individuals in the study compared to other recruitment modalities.

Perceptions, attitudes, and willingness of healthcare and frontline workers to participate in an Ebola vaccine trial in Uganda

BACKGROUND

Understanding the knowledge, perception and attitudes towards Ebola vaccines is an important factor in ensuring future use of these vaccines. A qualitative methods study embedded in an Ebola vaccine immunogenicity and safety trial (NCT04028349) was conducted to explore the knowledge and perceptions of healthcare (HCWs) and frontline workers (FLWs), about Ebola vaccines and their willingness to participate or recommend participation in Uganda.

METHOD

We carried out focus group discussions and semi-structured interviews before and after vaccination, with 70 HCWs and FLWs who consented to participate in the trial, and in the qualitative component, from August to September 2019. Data were analysed using thematic content analysis.

RESULTS

Respondents showed good knowledge about Ebola and the vaccines in general, and had wide access to information through several channels, including the study team. On prevention, particular attention was given to effective communication within health facilities. Misconceptions were mainly around route of transmission, animal origin and types of vaccines. Previous fears were based on rumours circulating in the community, mainly about the presence of the virus in the vaccine, side effects and intention to harm (e.g. by "the whites"), ultimately insisting on transparency, trust and involvement of local leaders. Acceptability of participation was motivated by the need to protect self and others, and the willingness to advance research. Majority were willing to recommend participation to their community.

CONCLUSIONS

Overall, information sharing leads to a better understanding and acceptance of vaccine trials and a positive vaccination experience can be a deciding factor in the acceptance of others. Particular attention should be paid to involving the community in addressing misconceptions and fears, while ensuring that participants have access to vaccination sites in terms of transport, and that they are properly accommodated at the study site including staying for a reasonable period of time.

Monitoring of Adverse Events in Recipients of the 2-Dose Ebola Vaccine Regimen of Ad26.ZEBOV Followed by MVA-BN-Filo in the UMURINZI Ebola Vaccination Campaign

BACKGROUND

From 2019 to 2021, Rwandan residents of the border with the Democratic Republic of the Congo were offered the Ad26.ZEBOV (adenovirus type 26 vector vaccine encoding Ebola virus glycoprotein) and MVA-BN-Filo (modified vaccinia virus Ankara vector vaccine, encoding glycoproteins from Ebola, Sudan, Marburg, and nucleoprotein from Tai Forest viruses) Ebola vaccine regimen.

METHODS

Nonpregnant persons aged ≥2 years were eligible. Unsolicited adverse events (UAEs) were reported through phone calls or visits, and serious adverse events (SAEs) were recorded per International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines.

RESULTS

Following Ad26.ZEBOV, UAEs were reported by 0.68% of 216 113 vaccinees and were more common in younger children (aged 2-8 years, 1.2%) compared with older children (aged 9-17 years, 0.4%) and adults (aged ≥18 years, 0.7%). Fever and headache were the most reported symptoms. All 17 SAEs related to vaccine were in children aged 2-8 years (10 postvaccination febrile convulsions ± gastroenteritis and 7 fever and/or gastroenteritis). The incidence of febrile seizures was 8 of 26 062 (0.031%) prior to initiation of routine acetaminophen in December 2020 and 2 of 15 897 (0.013%) thereafter. Nonobstetric SAEs were similar in males and females. All 20 deaths were unrelated to vaccination. Young girls and adult women with UAEs were less likely to receive the second dose than those without UAEs. Seven unrelated SAEs occurred in 203 267 MVA-BN-Filo recipients.

CONCLUSIONS

Postvaccination febrile convulsions in young children were rare but not previously described after Ad26.ZEBOV and were reduced with routine acetaminophen. The regimen was otherwise safe and well-tolerated.

Current Advances in Zika Vaccine Development

Zika virus (ZIKV), an emerging arthropod-borne flavivirus, was first isolated in Uganda in 1947 from monkeys and first detected in humans in Nigeria in 1952; it has been associated with a dramatic burden worldwide. Since then, interventions to reduce the burden of ZIKV infection have been mainly restricted to mosquito control, which in the end proved to be insufficient by itself. Hence, the situation prompted scientists to increase research on antivirals and vaccines against the virus. These efforts are still ongoing as the pathogenesis and immune evasion mechanisms of ZIKV have not yet been fully elucidated. Understanding the viral disease mechanism will provide a better landscape to develop prophylactic and therapeutic strategies against ZIKV. Currently, no specific vaccines or drugs have been approved for ZIKV. However, some are undergoing clinical trials. Notably, different platforms have been evaluated for the design of vaccines, including DNA, mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, peptide and protein-based vaccines, passive immunizations by using monoclonal antibodies (MAbs), and vaccines that target vector-derived antigens. These vaccines have been shown to induce specific humoral and cellular immune responses and reduce viremia and viral RNA titers, both in vitro and in vivo. This review provides a comprehensive summary of current advancements in the development of vaccines against Zika virus.

Adenovirus-Based Vaccines and Thrombosis in Pregnancy: A Systematic Review and Meta-analysis

BACKGROUND

Rare cases of thrombosis and thrombocytopenia (thrombosis with thrombocytopenia syndrome [TTS]) have been associated with 2 coronavirus disease 2019 adenovirus vector vaccines: the ChAdOx1 nCoV-19 Vaxzevria vaccine (Oxford/AstraZeneca) and the JNJ-7836735 Johnson & Johnson vaccine (Janssen). It is unknown if TTS is a class-mediated effect of adenovirus-based vaccines or if it could worsen known hypercoagulable states. Since most cases of TTS happen in women of childbearing age, pregnancy is a crucial risk factor to assess. Understanding these risks is important for advising vaccine recipients and future adenovirus vector vaccine development.

METHODS

To explore the potential associations of adenovirus-based vaccine components with symptoms of TTS in the general clinical trial population and in pregnant women in clinical trials, we conducted a systematic review and meta-analysis of adenovirus-based vector vaccines to document cases of thrombocytopenia, coagulopathy, and or pregnancy from 1 January 1966 to 9 August 2021.

RESULTS

We found 167 articles from 159 studies of adenovirus vector-based vaccines, 123 of which targeted infectious diseases. In the general population, 20 studies reported an event of thrombocytopenia and 20 studies indicated some coagulopathy. Among pregnant women, of the 28 studies that reported a total of 1731 pregnant women, thrombocytopenia or coagulopathy were not reported.

CONCLUSIONS

In this systematic review and meta-analysis, there was no class-wide effect of adenovirus vector vaccines toward thrombocytopenia or coagulopathy events in the general population or in pregnant women.

Safety, reactogenicity, and immunogenicity of a 2-dose Ebola vaccine regimen of Ad26.ZEBOV followed by MVA-BN-Filo in healthy adult pregnant women: study protocol for a phase 3 open-label randomized controlled trial

BACKGROUND

Risks to mother and fetus following Ebola virus infection are very high. Evaluation of safety and immunogenicity of non-replicating Ebola vaccine candidates is a priority for use in pregnant women. This is the protocol for a randomized, open-label, single-center phase 3 clinical trial of the safety, reactogenicity, and immunogenicity of the 2-dose Ebola vaccine regimen in healthy adult pregnant women. This 2-dose regimen has been shown to be safe, judged effective, and approved in non-pregnant populations.

METHODS

A total of 2000 adult (≥ 18 years of age) pregnant women will be enrolled from antenatal care facilities in Western Rwanda and randomized (1:1) to receive the 2-dose Ebola vaccine regimen (Ad26.ZEBOV, MVA-BN-Filo (group A)) or control (unvaccinated pregnant women (group B)). The primary objectives are to (1) assess adverse maternal/fetal outcomes in randomized pregnant women up to 1.5 months after delivery and (2) assess adverse neonatal/infant outcomes in neonates/infants born to randomized women up to 3.5 months after birth. The frequency and relatedness of all serious adverse events in women and newborns from randomization or birth, respectively, until study end will be reported. The reactogenicity and unsolicited adverse events of the 2-dose Ebola vaccine regimen in all vaccinated pregnant women (group A) will be reported. We will also assess the immunogenicity of the 2-dose Ebola vaccine regimen in 150 pregnant women who are anticipated to receive both vaccine doses within the course of their pregnancy (a subset of the 1000 pregnant vaccinated women from group A) compared to 150 non-pregnant women vaccinated after delivery (a subset of group B). The persistence of maternal antibodies in 75 infants born to women from the group A subset will be assessed. Exploratory analyses include assessment of acceptability of the 2-dose Ebola vaccine regimen among group A and assessment of maternal antibodies in breast milk in 50 women from group A and 10 controls (women from group B prior to vaccination).

DISCUSSION

This study is intended to support a label variation to relax restrictions on use in pregnant women, a vulnerable population with high medical need.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04556526 . September 21, 2020.

Third-generation smallpox vaccine strain-based recombinant vaccines for viral hemorrhagic fevers

Vaccinia virus has been used as a smallpox vaccine. Now that smallpox has been eradicated, the vaccinia virus is expected to be used as a bioterrorism countermeasure and a recombinant vaccine vector for other infectious diseases, such as viral hemorrhagic fevers. Many vaccinia virus strains were used as smallpox vaccines in the smallpox eradication campaign coordinated by the World Health Organization. These strains can be classified into generations, according to the history of improving production methods and efforts to reduce the adverse reactions. Significantly, the third-generation of smallpox vaccine strains, which include modified vaccinia Ankara (MVA) and LC16m8, are currently popular as recombinant vaccine vectors due to their well-balanced safety and immunogenicity profiles. The present review firstly focuses on the characteristics of the smallpox vaccine generations. The historical background of the development of the third-generation smallpox vaccine strains is detailed, along with the history of the transition of the vaccinia virus generation used as vectors for hemorrhagic fever vaccines to the third generation. Among the vaccinia viruses, MVA is currently the most commonly used vector for developing hemorrhagic fever vaccines, including dengue fever, yellow fever, Ebola viral disease, Lassa fever, Rift Valley fever, and Crimean-Congo hemorrhagic fever. LC16m8 is a vaccine candidate for severe fever with thrombocytopenia syndrome. The current status and recent advances in the development of these hemorrhagic fever vaccines using third-generation vaccinia strains are discussed.

Novel approaches for vaccine development

Vaccines are critical tools for maintaining global health. Traditional vaccine technologies have been used across a wide range of bacterial and viral pathogens, yet there are a number of examples where they have not been successful, such as for persistent infections, rapidly evolving pathogens with high sequence variability, complex viral antigens, and emerging pathogens. Novel technologies such as nucleic acid and viral vector vaccines offer the potential to revolutionize vaccine development as they are well-suited to address existing technology limitations. In this review, we discuss the current state of RNA vaccines, recombinant adenovirus vector-based vaccines, and advances from biomaterials and engineering that address these important public health challenges.

Injection site vaccinology of a recombinant vaccinia-based vector reveals diverse innate immune signatures

Poxvirus systems have been extensively used as vaccine vectors. Herein a RNA-Seq analysis of intramuscular injection sites provided detailed insights into host innate immune responses, as well as expression of vector and recombinant immunogen genes, after vaccination with a new multiplication defective, vaccinia-based vector, Sementis Copenhagen Vector. Chikungunya and Zika virus immunogen mRNA and protein expression was associated with necrosing skeletal muscle cells surrounded by mixed cellular infiltrates. The multiple adjuvant signatures at 12 hours post-vaccination were dominated by TLR3, 4 and 9, STING, MAVS, PKR and the inflammasome. Th1 cytokine signatures were dominated by IFNγ, TNF and IL1β, and chemokine signatures by CCL5 and CXCL12. Multiple signatures associated with dendritic cell stimulation were evident. By day seven, vaccine transcripts were absent, and cell death, neutrophil, macrophage and inflammation annotations had abated. No compelling arthritis signatures were identified. Such injection site vaccinology approaches should inform refinements in poxvirus-based vector design.

Poxvirus vector systems have been widely developed for vaccine applications. Despite considerable progress, so far only one recombinant poxvirus vectored vaccine has to date been licensed for human use, with ongoing efforts seeking to enhance immunogenicity whilst minimizing reactogenicity. The latter two characteristics are often determined by early post-vaccination events at the injection site. We therefore undertook an injection site vaccinology approach to analyzing gene expression at the vaccination site after intramuscular inoculation with a recombinant, multiplication defective, vaccinia-based vaccine. This provided detailed insights into inter alia expression of vector-encoded immunoregulatory genes, as well as host innate and adaptive immune responses. We propose that such injection site vaccinology can inform rational vaccine vector design, and we discuss how the information and approach elucidated herein might be used to improve immunogenicity and limit reactogenicity of poxvirus-based vaccine vector systems.