The arrival of new Covid-19 variants is seen as one of the main dangers, which could intensify the crisis and delay the fight against the viral disease, according to British experts quoted by 'The Guardian.

Graham Medley, a member of the UK science advisory group (Sage), believes that the emergence of new variants is "clearly something that scientists should take very seriously, because it could set us on a long road."

"A new variant, capable of resisting immunity, would essentially be a new virus," he said. "The advantage is that we know we can generate vaccines against that virus - and relatively quickly. The disadvantage is that we would be back to the same situation we were in a year ago," he stressed to the paper.

For his part, Marc Baguelin, a member of the Covid-19 response team at Imperial College, argued that preventing the importation of variants of concern, with "moderate to high immune resistance properties will be critical, because their spread could lead to future waves, more severe than those recorded so far."

"This new virus is unlikely to fully resist immunity from previous infections or vaccines," the expert said. "Some immunity should remain at least in the most severe cases," he added stressing that "we would probably be able to update current vaccines to include the new strain."

However, he warned, "doing this takes months and means that we may have to impose restrictions again if there is a significant public health risk. The level of restrictions should be proportionate to the amount of virus that resists current vaccines," he argued.

The Covid-19 pandemic has already caused 207.2 million infections worldwide, as well as 4.3 million deaths, according to a count by Johns Hopkins University in the United States.