NEW YORK: Bill Gates said some schools may not be back to normal until the fall of 2021, he warned that any vaccine against coronavirus could take several doses to be effective, as he described 'serious mistakes' made by the Trump administration. 

Gates, 64, emphasized that key to combating the virus was social distancing, wearing masks, and developing a vaccine. And Gates said that the closure of schools was among his biggest concerns. 'I'd put that, after the deaths, as the next biggest cost,' he said.

This next academic year does hang in the balance, he continued. 'It's extremely important. You want the staff to feel safe, that you're taking measures on their behalf. You want the learning to resume. “Sadly the suburban and private schools are doing a lot better at putting learning online. It's the inner cities that don’t have the resources.”

The Microsoft founder, who now directs much of his time and energy to his global health foundation, said that the closure of schools was, after deaths, the 'biggest cost' of the pandemic.

And, in an interview with Norah O'Donnell on CBS News, aired on Wednesday night, theSeattle-based billionaire was critical of Donald Trump’s handling of the crisis. “Opening up bars — the economic benefit versus the infection risk - a lot of policies like that made it a mistake.'