COVID-19
– possibly in regions where implementation of control measures has been resisted – might make ideal trial locations, due to a potentially richer pool of infections in which to treat or prevent the disease.
“If patient pools for inclusion in Covid-19 trials continue to shrink, developers may have to rely on predicting which regions may not effectively control the outbreak, something that is extremely difficult.”
This situation is reminiscent of the Zika virus epidemic of 2015–16, where developers rapidly began intense development of therapeutic and prophylactic interventions. However, as the outbreak was contained less than two years after its initiation, due to implementation of mosquito control measures, developers had no patients left to include in trials for treatments. Similarly, a lack of spread of the virus also meant it would be nearly impossible to demonstrate any effectiveness of a vaccine; therefore, development of nearly all Zika virus interventions came to a halt. If patient pools for inclusion in Covid-19 trials continue to shrink, developers may have to rely
on predicting which regions may not effectively control the outbreak, something that is extremely difficult. They may also try to anticipate areas where a second wave or rebound of the outbreak could occur, but must also consider that if faced with a second wave, authorities may impose even stricter restrictions than they did for the first wave in order to rapidly control the outbreak, which would limit patient pools.
Within limits One potential way of demonstrating a vaccines’ effectiveness could be challenge studies, where patients receive a vaccine and are then challenged with a given pathogen. While not an acceptable substitute for standard clinical trials, this type of study could be useful for determining which vaccines should be moved into proper clinical studies and ease competition for what might be a vanishing patient pool. Challenge studies are great for proof of principle, but they have their limitations. They might not reflect protection conferred by whatever strain of the pathogen is circulating and they cannot be conducted with pathogens that are associated with severe diseases for ethical reasons. Additionally, they are used largely for vaccines, not treatments. Should numbers of infected patients decrease substantially, trials for treatments may be postponed until the outbreak re-emerges. ●
96 | Outsourcing in Clinical Trials Handbook
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