World Health Organization director-general Tedros Adhanom Ghebreyesus asked countries that have booked excess vaccine doses to "donate and release them to Covax immediately.
He said SAGE did not recommend the Pfizer jab for travellers unless they were in a very high-risk group due to the very limited supply of anti-COVID drugs at present.
The fighting in Tigray has left thousands dead, according to the International Crisis Group think tank, and sent tens of thousands of refugees streaming across the border into Sudan.
Announcing the agency had secured nearly two billion doses of vaccine candidates, the WHO said in a statement that this would "enable all participating economies to have access to doses in the first half of 2021, with first deliveries anticipated to begin in the first quarter of 2021."
"Working in a healthcare facility without water, sanitation and hygiene is akin to sending nurses and doctors to work without personal protective equipment," said WHO chief Tedros Adhanom Ghebreyesus.
"This is a dangerous virus, which can attack every system in the body. Those countries that are letting the virus run unchecked are playing with fire," he said.
The WHO advance team that travelled to China has now concluded their mission to lay the groundwork for further joint efforts to identify the virus origins, the agency's chief Tedros Adhanom Ghebreyesus told a virtual press conference.
"More than six months into the pandemic this is not the time for any country to take its foot off the pedal," WHO Director General Tedros Adhanom Ghebreyesus told an online briefing.
WHO chief Tedros Adhanom Ghebreyesus said US involvement with the organisation had made a "great difference" over the decades and "it is WHO's wish for this collaboration to continue".