86.64 per cent of people in the Greater Mumbai area have COVID-19 antibodies - meaning they have been exposed to the coronavirus at least once - according to the results of a sero-survey conducted between August 12 and September 9 in anticipation of a third wave of infections. The Brihanmumbai Municipal Corporation, the city's civic body, has warned people that estimated sero-prevalence levels do not necessarily indicate high protection levels.