In an encouraging development, an experts' report late on Tuesday pointed to Mumbai heading towards 'herd immunity' as the city recorded the lowest number of cases -- 700 -- in the past three months on Tuesday, officials said.

The ser-survey report prepared by the NITI Aayog, Tata Institute of Fundamental Research and BrihanMumbai Municipal Corporation (BMC) indicates that Mumbai, which currently has a little more than 21,000 active cases, could be inching towards herd immunity.

The recovery rate in Mumbai is 73 per cent while the doubling rate has climbed to 69 days.

So far, BMC has done over 4.85 lakh tests and the overall growth from July 20 to July 26 is 1.03 percent.

"The first round report of Sero Surveillance for COVID-19 infection in Mumbai indicates that 57 percent of slum population and 16 percent of non-slum population have developed antibodies. The infection fatality rate is very low. Are we closer to herd immunity?" BMC's Additional Municipal Commissioner Ashwini Bhide tweeted late on Tuesday.

A BMC statement later said: "The results will be valuable to learn more about herd immunity. Although it is still unclear what level of prevalence leads to herd immunity, findings indicate at least in slums this could be attained sooner or later, if the immunity exists and persists in a significant proportion of the population."

About 57 percent respondents in Mumbai slums had been exposed to COVID-19, as opposed to 16 percent in non-slum areas, showed the sero-survey report. Sero-prevalence was marginally higher in women than men, showed the study. (IANS)