In June 2023 CEPI issued a Call for Proposals for research teams interested in collaborating with the European Union’s Horizon programme on a consortium to create a human-challenge-model platform to test novel mucosal vaccine candidates against betacoronaviruses. This is the sub-family of coronaviruses that includes the SARS-CoV-2 virus and MERS coronavirus. The pursuit of mucosal immunity is a goal emphasised by lessons from the COVID-19 pandemic, during which powerful vaccines were created in record time; however, they were unable to “efficiently prevent people from becoming infected”. 

“The vaccines do not always block the virus. They do not stop disease transmission.” 

Although these vaccines were effective tools in the fight against the pandemic, a need has been identified. CEPI is driving a new project to break the chains of viral transmission to prevent epidemics expanding into pandemics. This project aims to use “human challenge” studies to understand the best vaccine design to achieve mucosal immunity.  

Challenge trials 

We heard from hVIVO’s Dr Andrew Catchpole about how his team approaches challenge trials with safety as a central focus, so if you would like to understand more about the work that hVIVO does click here. Challenge trials involve infecting healthy volunteers with the virus to understand if and how a vaccine works. Also called Controlled Human Infection Models (CHIM), challenge studies are particularly useful for offering “new and deeper insights” into vaccines, says Dr Christin Dahlke, CEPI’s Translational Immunology Lead.  

“It’s crucial that we improve our understanding of how transmission of such viruses can be blocked using vaccines.” 
Benefits compared to other approaches 

CEPI acknowledges that “large clinical trials and real-world follow-up studies are the gold-standard approach” to establish efficacy and effectiveness of safe and developed vaccines. However, this research isn’t able to identify “specific immune markers” that can be used as “clues to how a vaccine might be designed to produce transmission-blocking mucosal immunity”.  

“Human challenge studies, on the other hand, offer scientists the chance to monitor participants on an hour-by-hour and day-by-day basis to check whether they have become infected, how, and what their immune system is doing in response.” 
Mucosal immunity 

CEPI notes that almost all viral respiratory diseases in humans “get in” through mucosal surfaces like saliva, inhaled droplets, or sexual contact. Therefore, using challenge studies to gain insight that will be useful for pathogenic viral threats “makes sense”. Dr Dahlke believes that we need to make quick progress. 

“What the world needs to be able to take the next steps towards creating infection-stopping vaccines is reliable data on, and established, standardised markers for immunity.”  

Through these studies, where participants are monitored on site for around two weeks, scientists can “get really good insights into what is going on.”  

Call for proposals 

Through the call for proposals CEPI is looking to fund up to two multi-country networks to conduct research. The aim is to establish “collaborative groups, processes, and procedures to conduct human challenge studies at the highest levels of safety, quality, reliability, and reproducibility”. Dr Dahlke hopes that these networks will “establish harmonised processes to test and compare vaccines”.  

“Fighting epidemics and pandemics is possible with disease-reducing vaccines, but it would be faster and more effective if we also had vaccines that can stop viral spread.”  

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