"We won't get back to normal quickly," Dale Fisher, chairman of the World Health Organization's (WHO) Outbreak Alert and Response Network, told the Reuters Next conference.
"We know we need to get to herd immunity and we need that in a majority of countries, so we are not going to see that in 2021," Fisher said.
"There might be some countries that might achieve it but even then that will not create 'normal' especially in terms of border controls."
Herd immunity refers to a situation where enough people in a population have immunity to an infection to be able to effectively stop that disease from spreading.
More than 90 million people are reported to have been infected by the novel coronavirus globally and about 1.9 million have died from the disease since it first emerged in China in December 2019, according to a Reuters tally.
Several countries including the United States, Singapore, Britain and a number of European Union countries have already begun rolling out vaccines such as those developed by Pfizer and its partner BioNTech, and by Moderna Inc and AstraZeneca Plc/Oxford University.