Published on 10 July, the results of the survey showed 44.5 per cent of those tested had antibodies against Covid-19.
The serological survey was conducted by a number of health bodies, including Jakarta's provincial health office, the Eijkman Institute for Molecular Biology and US Centers for Disease Control and Prevention staff based in Indonesia.
It indicated that about 4.7 million of the total 10.6 million people in the Indonesian capital may have been infected by 31 March, according to CNN.
This is at least 12 times the number of confirmed cases — 382,000 — of Covid-19 reported in Jakarta until that time. The infections had surged to more than 689,000 by Tuesday.
The survey was conducted among 5,000 people across the city. Widyastuti, the head of the city's health department, said this showed the extent of the pandemic in Jakarta.
The proportion of Jakarta residents infected by Covid-19, whether confirmed by an RT-PCR test or not, can be estimated through the survey, the official said, according to a report in the Jakarta Globe newspaper. The survey has given a complete picture, making it possible to adjust pandemic handling strategies, according to Widyastuti.
The report found infection rates were higher in women, with most of the infected people aged between 30 and 49 years.
Experts have warned that the official number of coronavirus cases in Indonesia is likely an undercount because of low rates of testing. The country recorded 47,899 new infections on Tuesday, surpassing India’s daily count.
The surge has been triggered by the Delta variant of Covid-19, which was first identified in India and has now spread to more than 100 countries.
The country’s healthcare infrastructure has come under massive strain with health minister Budi Gunadai Sadikin saying nine provinces, including Jakarta and West Java, reported hospital bed occupancy to be above 80 per cent.
Authorities are now planning to order liquid oxygen and concentrators from abroad as the demand for oxygen has surged, according to news agency Reuters.