The largest Ebola outbreak in history is defying the containment efforts of affected countries and international response teams, leading to calls from some quarters to use experimental drugs or vaccines to try to stop the deadly virus.

But a number of experts — including the scientist who led the work on a Canadian-made Ebola vaccine — say deploying untested tools in the current West African outbreak could be disastrous.

They say taking such a risky gamble could further erode local trust in the response teams, undermine their efforts and even endanger them. And if anyone were to have a bad reaction to one of the experimental therapies, it could jeopardize years of expensive and painstaking work spent developing tools with which to fight Ebola and its cousin, the Marburg virus.

“I get emails basically every second day from someone either asking ‘Is there something that you’re planning?’ or ‘Shouldn’t you?’…