China's top respiratory disease expert has warned every nation in the world is at risk from Covid-19 until global herd immunity is achieved, suggesting that might not happen until 2024.
Dr Zhong Nanshan warned mass vaccination globally could take up to three years at a Science Council of Asia conference on Thursday, the Global Times reported.
He said it was vital to achieve as soon as possible, with first world countries such as Australia remaining at risk if poorer, virus-ravaged nations are left behind.
"No country is safe until all countries are safe," Dr Zhong said.
Dr Zhong's comments come as a map from Our World in Data shows the low rate of vaccination in most of the world's nations apart from a select few.
The map does not capture the situation in Australia, as the organisation doesn't have data on vaccination rates here, but the Morrison government has repeatedly come under fire over the delays in the vaccination program.
United Nations Secretary-General Antonio Guterres has also recently called on the world to double vaccine production to assist the developing world.
"It is totally unacceptable to live in the world, in which developed countries can vaccinate most of its population, while many developing countries have not access to one single dose," Mr Guterres said.
He said as the virus spreads "like wildfire" in some nations, the chances of highly-infectious mutations was increasing.
"It's in the interest of everybody that everybody is vaccinated everywhere," he warned.
Epidemiologist Professor Raina MacIntyre, Head of the Biosecurity Program at UNSW, previously told Yahoo News Australia there is no guarantee that if Australia is vaccinated its borders would open.
"Variants of concern may arise which are resistant to vaccines – for example, the AstraZeneca vaccine has 0-10 per cent efficacy against the South African variant."
In a recent paper, Prof MacIntyre noted if vaccines have an efficacy of less than 70 per cent, herd immunity cannot be achieved and Australians will be at risk of potential outbreaks.
Australia's vaccine rollout has been plagued by complications, and with a drop in confidence for Australia's main vaccine, in terms of quantity, the AstraZeneca jab, reaching herd immunity in Australia this year is becoming increasingly unlikely.
The Federal Budget's estimations of a mid-2022 return to international travel has provided an indication of the Morrison government's best hopes.
As India's virus cases surged last month, Dr Zoe Hyde, an epidemiologist at the University of Western Australia, warned any country could face a similar outbreak if it attempts to "live with the virus".
"No country is safe until herd immunity has been reached by vaccination," she explained.
AstraZeneca jab needs to be ditched, expert warns
In a recent submission to the Asia & The Pacific Policy Society's Policy Forum, Dr Hyde, alongside Environmental Economics and Biosecurity Professor Tom Kompas from the University of Melbourne and ANU professor of economics Quentin Grafton, warned Australia it must put its focus on vaccines with the highest efficacy, such as Moderna and Pfizer.
On Thursday, Health Minister Greg Hunt announced the acquisition of 25 million Moderna doses to go with the 40 million doses of Pfizer already acquired.
Dr Hyde explained it was "inequitable" to continue to give the AstraZeneca jab to Australians above 50.
"It knowingly gives older people, who face a higher risk of severe disease and death from Covid-19, a less effective vaccine.
"It also runs the risk of creating a situation where the South African variant could spread in Australia’s older population should border controls be relaxed or if an outbreak should occur."
She argues the AstraZeneca vaccine should only be used as an emergency option.
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