COVID-19 has years to run according to the former New Zealand PM who has been asked to investigate the origins and handling of the pandemic.
On Friday, the World Health Organisation (WHO) announced Helen Clark, along with former Liberian president Ellen Johnson Sirleaf, will lead an evaluation commission into the deadly virus.
Labelling the task "exceptionally challenging", Ms Clark said options including beefed-up powers for the WHO should be on the table to prevent further crises.
She warned a mass COVID-19 vaccination program was not likely until 2023 at the earliest.
"This is going to roll for years," she told Australian Associated Press.
"What I'm hearing is the most optimistic forecast for a more widely available vaccine is two and a half years away.
"There are discussions going on about a vaccine rolling out to essential workers, like the health force and then to vulnerable groups ... maybe 20 per cent of the population at the end of next year. That is also optimistic.
"In the worst case scenario we'll see it rolling on for three or four years with 60 per cent of people affected around the world.
"This is not great."
Ms Clark is one of New Zealand's most experienced international assets, as a former head of the UN's Development Programme.
The WHO-commissioned Independent Panel for Pandemic Preparedness and Response (IPPR) will analyse the coronavirus' beginnings and how to prevent the future outbreak of pandemics, as well as how individual members responded to the virus.
Ms Clark has tabled a pandemics convention as one option for the WHO that "has to be examined".
"The WHO has almost no powers whereas if you look at a sister UN agency, the International Atomic Energy Agency, it does have powers," she said.
"If you sign on to that, you're expected to allow inspectors to enter and so on.
"The idea of a convention which would see states accept responsibility is quite a good one. The issue is whether you get as much cooperation."
New Zealand has been recognised globally for its response to COVID-19, eliminating the virus from the community and running a largely effective border regime.
The IPPR will give a progress report in November before concluding its work in May next year.