Acting chief medical officer Paul Kelly says papers published in the past few weeks show several types of vaccines appear effective at making antibodies against COVID-19.

"I'm much more hopeful than I was even a few weeks ago," he told reporters in Canberra on Friday.

He said the possible vaccines appeared to make antibodies against the virus, which remain for a few months.

"We don't know about the long term yet. That will be something we'll find out as time goes by," Professor Kelly said.

He said some clinical trials were also looking to scale up manufacturing, with more to be known in coming weeks and months.

Prime Minister Scott Morrison reiterated his call for other countries to guarantee if they found a vaccine to make it available across the globe.

"We pledge that if we find the vaccine we'll share it. I think every country's leader should say that," he said.

"Any country that were to find this vaccine and not make it available around the world, without restraint, I think would be judged terribly by history."

Australian Associated Press