FOCUS: Human Challenge Trials Gain Ground in Europe; Japan Cautious

Tokyo, Nov. 12 (Jiji Press)–Controlled human infection model, or CHIM, trials, in which carefully screened volunteers are deliberately exposed to calibrated doses of pathogens, are primarily used in a number of European countries, but Japan remains wary. CHIM trials, also known as human challenge studies, are considered a more efficient way to evaluate the efficacy and safety of candidate medicines than conventional methods. In Japan, concerns over risks, including severe illness and potential long-term effects, have fueled strong opposition, and the government remains cautious about adopting the approach. CHIM trials can shorten development timelines and reduce participant numbers by not waiting for participants to encounter the pathogen in everyday life, unlike conventional trials. In a late August interview with Jiji Press and other media outlets, Dr. Pierre Van Damme, director of Vaccinopolis, a clinical trial facility operated by the University of Antwerp’s Centre for the Evaluation of Vaccination, underscored the value of CHIM trials. “If we had developed vaccines earlier, we would have reduced mortality even more,” Van Damme said of the COVID-19 pandemic. Vaccinopolis houses 30 beds dedicated to CHIM, the largest capacity worldwide. Van Damme noted that conventional trials often enroll 1,000 to 40,000 participants and run for several years, whereas CHIM studies can reduce this to 20 to 200 participants over just a few months. Vaccinopolis is currently conducting human challenge trials of therapeutics for infectious diseases such as influenza and malaria. To minimize the risk of severe illness, enrollment is generally limited to healthy adults aged 18 to 40. Participants receive round-the-clock medical supervision, with physicians ready to respond immediately to any sudden change in condition. Britain announced in 2020 that it would launch CHIM trials to accelerate COVID-19 vaccine development. The government committed 33.6 million pounds to support collaborations among universities and industry partners. Germany and the Netherlands have likewise used such trials for certain infectious diseases with low mortality. In Japan, by contrast, both safety and ethical concerns have slowed the adoption of CHIM trials. Some critics worry that such trials could be perceived as “human experimentation.” Reflecting these reservations, the government’s medical research and development promotion plan, released in February, pointed to the “ethical and safety issues” surrounding CHIM and said any introduction would be considered “with care.” At a research meeting to draw up the plan, a vaccine safety evaluation expert warned that CHIM trials involve “considerably high risk.” Recalling human experiments with biological weapons conducted by the former Imperial Japanese military before and during World War II, another expert cautioned that the issue was “sensitive for the Japanese people.” The World Health Organization’s ethics guidance published in 2021 emphasized the safety of CHIM trials, noting that studies in recent decades have been conducted “with very few reported serious or lasting harms.” The WHO further maintained that such research conducted under stringent ethical standards should be distinguished from wartime human experimentations, an assessment that stands in contrast to the Japanese government’s stance. An official at the Cabinet Office involved in drafting the research and development promotion plan raised concerns about the risk of severe illness, stressing that it is “out of the question for a participant (in a CHIM trial) to die.” An official at the Ministry of Health, Labor and Welfare, which leads discussions on whether to introduce CHIM trials in Japan, warned that the adoption “should not be decided easily.” The official indicated the ministry’s plans to first review implementations, including in Belgium, to identify specific safety and ethical issues. END [Copyright The Jiji Press, Ltd.]