Modeling studies have revealed that about 60 to 70 per cent of the global population needs to be immune to curb or halt COVID-19 transmission, a World Health Organization (WHO) official said.

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Noting the WHO cannot give the exact number of "the proportion of the population that would need to be immunized... The answer to that can come from modeling studies", Xinhua news agency quoted Katherine O'Brien, director of WHO's Department of Immunization, Vaccines and Biologicals, as saying at a virtual briefing on November 27.

"These modeling studies under a variety of conditions have concluded that somewhere around 60 to 70 per cent of the population would need to be immune, presumably through immunization, in order to achieve a reduction or an interruption of transmission of the virus. "That's of course predicated on what the performance of the vaccines would be," she added.

The remarks come as overall number of global coronavirus cases has topped 61.5 million, while the deaths have surged to more than 1.44 million, according to the Johns Hopkins University. In its latest update on Saturday, the University's Center for Systems Science and Engineering (CSSE) revealed that the current global caseload and death toll stood at 61,585,651 and 1,441,875, respectively.

The US is the worst-hit country with the world's highest number of cases and deaths at 13,086,367 and 264,842, respectively, according to the CSSE. India comes in second place in terms of cases at 9,309,787, while the country's death toll soared to 135,715.

In the same virtual briefing on Friday, Maria Van Kerkhove, technical lead for WHO's Health Emergencies Program, said that countries with decreasing Covid-19 numbers still need to stay "vigilant". "Even as case numbers are coming down, all countries need to remain vigilant. You've heard of this before, but we really need to emphasize it again. Do not let your guard down.

"It's good to see the measures taking effect and transmission going down. But it's not time to let up. It's time to even scale up. "What we don't want to see is situations where you are moving from a so-called lockdown state to bring the virus under control to moving to a so-called lockdown state," she added.