Delhi had on Thursday reported 2,668 cases with a positivity rate of 4.3 per cent, and 13 deaths.
Researchers found that among 24 reported cases, Delta was seven-fold more likely to lead to vaccination breakthrough infections than non-Delta lineages.
Only one fatality due to coronavirus has been reported this month, on September 7, as per the official figures.
Twenty-five fresh cases of Covid-19, the lowest since April 15 last year, and two deaths due to the disease were recorded on Thursday, August 19, while the positivity rate stood at 0.04 per cent.
Not received any letter from Centre seeking info on deaths due to oxygen scarcity in Delhi: Deputy CM
'I read in newspaper reports that the Centre is saying that it has asked state governments to share the number of oxygen-related deaths,' Delhi Deputy Chief Minister Manish Sisodia said.