Ryan noted that while the covid-19 pandemic has certainly been very severe, it wasn't "necessarily the big one" that experts have been dreading.
More than 1.7 million people worldwide have died this year from Covid-19, more than 81 million cases have been recorded and the spread of the coronavirus has been unrelenting in many countries. "We must all learn the lessons the pandemic is teaching us", he said.
Dr. Ryan said the virus is "very transmissible, and it kills people. its current case fatality (rate) is reasonably low in comparison to other emerging diseases".
"The planet is fragile, we live in an increasingly complex, global society. We need to get ready for something which may be even more severe in the future".
In a conference marking one year since the WHO was first informed about the virus in China, Dr Tedros Adhanom Ghebreyesus praised the "incredible scientific achievement" which has seen a vaccine created and distributed to countries across the world in under a year.
"We are into second and third waves of this virus and we are still not prepared to deal with and manage those", Aylward told the briefing.
But one element of emergency preparedness that needs to improve before the next outbreak, Ryan said, was the ability of the public to be able to follow guidelines.
The Director-General of the World Health Organization (WHO) said today it "will not rest" until all countries across the world have access to the coronavirus vaccine.
EU starts COVID-19 vaccine campaign
In France, a 78-year-old woman received a shot at a hospital in a Paris suburb, becoming the first person in the country to do so. In Prague, Czech Prime Minister Andrej Babis received his shot at dawn Sunday and asserted: "There's nothing to worry about".
But he stressed that it was "time now to be really serious".
"In terms of awareness, I think we are now getting it", he said.
"More ambition will be necessary".
But Tedros also hailed how scientists around the world were working closely together to help bring the pandemic to an end.
"We need to honour those we've lost by getting better at what we do every day", World Health Organization chief scientist Dr Soumya Swaminathan during the briefing.
He spoke about the new variants of the coronavirus detected in the United Kingdom and South Africa, which he said was possible due to the two countries carrying out epidemiologic and laboratory studies.