2-year - old girl dies . Forty - three countries are being monitored . Standards will have to be met for any mass vaccination program , WHO says . `` It 's clear that it remains quite a challenge right now . WHO also says that more potential Ebola vaccines are to start clinical trials soon .
2-year - old girl dies . Forty - three countries are being monitored . Standards will have to be met for any mass vaccination program , WHO says . WHO also says that more potential Ebola vaccines are to start clinical trials soon .