"He has shown significant improvement in the last 48 hours. His kidney function is normal and his urine output is nearly normal now. The infection is under control and the blood pressure, respiratory function and hearty rate are normal. They are being maintained without any support," Randeep Guleria, AIIMS Director, said this afternoon.
"We are hopeful he will make a full recovery in the next few days. We will be able to send him back home after that," Mr Guleria added.
Yesterday, in a medical bulletin, doctors said Mr Vajpayee is stable and on injectable antibiotics. He had undergone dialysis on Monday.
Since he was admitted, the former PM has had high-profile visitors including Prime Minister Narendra Modi, BJP chief Amit Shah, Congress president Rahul Gandhi, former prime minister Manmohan Singh and RSS chief Mohan Bhagwat.
Mr Vajpayee, the first non-Congress PM to complete a five-year term, has been away from public life since 2009, and has not been seen leaving his home in Delhi.
In 2009, the BJP patriarch was admitted to hospital just 48 hours before a party leadership meeting in Nagpur. That was when he stepped away from active politics.
Mr Vajpayee, one of the BJP's tallest leaders, ruled the country for 13 days in 1996, 13 months in 1998 and for almost six years from 1999.