Efforts to beat back the coronavirus are critical. They’re also making clinical trials harder

In March, a team of Chinese scientists studying whether the antiviral remdesivir was effective against Covid-19 ran into a problem. “Stringent public health measures used in Wuhan led to marked reductions in new patient presentations,” the researchers wrote. Without enough patients enrolled, the study ended early.

Last month, another Chinese team reported that a trial of the drug hydroxychloroquine had bumped into similar issues. “The recruitment of eligible patients was unexpectedly difficult,” the scientists wrote, explaining they had failed to reach their enrollment goal.

The snags reflect one of the paradoxes of infectious disease research — and one that could make it challenging to test experimental drugs and vaccines for Covid-19. When public health officials succeed in stamping out outbreaks, they also make it more difficult for researchers to find the volunteers they need for clinical trials. Earlier trials of drugs and vaccines for Zika and Ebola were stymied by such obstacles.