The survey, conducted between October and December by researchers at the University of Indonesia, found Indonesians had developed antibodies from a combination of COVID-19 infections and vaccinations.
Pandu Riono, an epidemiologist involved in the survey that covered some 22,000 respondents, said the level of immunity could explain why there had not been a significant jump in COVID-19 infections since the middle of 2021.
Indonesia's second wave of infections - driven by the Delta variant - peaked in July and August, with infections plummeting from more than 50,000 a day to just a few hundred a day in recent months.
The antibodies may provide some protection against new variants, including the highly contagious Omicron, Pandu said, though adding it would take months for this to become clear.
Omicron has infected more than 250 people in Indonesia, but most cases have been imported and a handful of local cases have not so far brought the type of surge recorded in many countries.
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