Cikeusal, Indonesia ? Holding her 2-year-old son, Sari listens intently in a ramshackle health clinic as the medical staff assures her and other villagers about the safety of the vaccine being used to fight Indonesia’s first polio outbreak in a decade.

But the impoverished mother of two remains unconvinced. She hints she will not participate in Tuesday’s nationwide immunization campaign because of unfounded rumors that a neighbor’s child contracted polio after being given the oral vaccine earlier this year.

“I’m afraid. Maybe my boy will get paralyzed,” said Sari, who was among 62 percent of parents in her village who refused to get their children vaccinated in June during a regional campaign on Java, the main island where most of the nation’s 226 polio cases have occurred.

Such fears are threatening the biggest public health exercise ever mounted in Indonesia, whose rising caseload has the World Health Organization worried that the virus could spread throughout Southeast Asia.

Indonesian leaders are pulling out all stops to win over a public skeptical about the drive to vaccinate 24 million children younger than 5 Tuesday and then again on Sept. 27.

More than 750,000 vaccinators will be on hand Tuesday at 245,000 posts.

“The biggest challenge is public trust,” said UNICEF’s Claire Hajaj.

She works on the U.N. agency’s global campaign to eradicate polio in the six countries where it remains endemic, as well as in Indonesia and 16 other nations that recently have been re-infected.

A 20-month-old diagnosed with polio in March was the country’s first case since 1995.

Indonesia’s polio outbreak first prompted authorities to vaccinate as many as 6.5 million children in Java province during two rounds earlier this year.

But officials missed 1 million children in the second round after parents were scared off by reports that three children died from taking the vaccine – later proven unfounded – or rumors that the vaccine violates Islamic law because it was produced using monkey kidney cells.

Islamic leaders in Indonesia sought to put such rumors to rest by issuing a fatwa saying the vaccine does not violate Muslim dietary law. But in provinces like West Java, which has 58 polio cases, that and other rumors persist.