Giving everyone in the world booster shots multiple times a year is not feasible, said the Oxford Vaccine Group Director Professor Andrew Pollard.
"We can't vaccinate the planet every four to six months. It's not sustainable or affordable," said Pollard, who is also the head of the UK's Committee on Vaccination and Immunisation, during an interview with The Daily Telegraph on Tuesday (4 January).
In a separate interview with Sky News on Tuesday, Pollard also cited the glaring unevenness of vaccine rollouts across the world.
"It is just not from a global perspective - affordable, sustainable or deliverable to give fourth doses to everyone on the planet every six months," Pollard said.
"And remember that, today, less than 10% of people in low-income countries have even had their first dose, so the whole idea of regular fourth doses globally is just not sensible," he added.
The "worst is behind us" and the world "just needs to get through the winter," he said adding that "at some point, society has to open up."
"When we do open, there will be a period with a bump in infections, which is why winter is probably not the best time."
He warned about the dangerous consequences of vaccine misinformation, highlighting that even "unintentional" comments from politicians can wreak havoc.
"Let's just say that comments made in mainland Europe affected people in Africa," he said.
Pollard stressed the "need to target the vulnerable" going forward, rather than administering doses to everyone age 12 and older.
More data is needed to ascertain "whether, when and how often those who are vulnerable will need additional doses," he said.