More than 20,000 front-line health care workers could become guinea pigs for two new experimental Ebola vaccines as early as January.

So far, more than 200 health care workers have died of the disease, most based in West Africa’s hot zone.

An effective vaccine wouldn’t in itself be enough to stop the outbreak – it’s unlikely there will be enough doses to go around – but it could give important protection to the medical workers who are central to the effort.

• Nurse in Ebola scare to leave isolation
• Nigeria officially declared Ebola-free

The WHO, which has come under fire for bungling its initial reaction to the Ebola crisis, is helping co-ordinate trials of two of the most promising experimental vaccines.

The real-world testing in West Africa will go forward only if the vaccines prove safe and trigger an adequate immune-system response in volunteers during clinical trials that are either underway or planned in Europe, Africa and the US. The preliminary safety data is expected to become available by December.

Dr Marie Paule Kieny, an assistant director general for the UN health agency, acknowledged there are many “ifs” remaining – and “still a possibility that it will fail”. But she sketched out a much broader experiment than was imagined only six months ago, saying WHO hopes to dispense tens of thousands of doses in the first couple of months of the new year.

“These are quite large trials,” she said on Tuesday.

WHO spokeswoman Fadela Chaib later said the agency expects 20,000 vaccinations in January and similar numbers in the months after that.

The outbreak in West Africa has killed over 4500 people, mostly in Liberia, Guinea and Sierra Leone, since it emerged 10 months ago.

Experts said the world could see 10,000 new cases a week in two months if authorities don’t take stronger steps.