DHAKA, Bangladesh (AP) _ More than a half million health workers and volunteers will fan out across Bangladesh on Sunday to immunize up to 24 million children under age 5 for polio, officials said.

The vaccinations are part of a three-phase campaign to eliminate polio from Bangladesh, S.M. Golam Kibria, a spokesman for the Health and Family Welfare Ministry, said Saturday.

In the first and second rounds of vaccinations, held April 16 and May 13 respectively, more than 20 million children were immunized, Kibria said. Bangladesh has a population of 144 million.

But on Sunday, the government is expected to reach their target of 24 million children, he said.

The children are to visit about 120,000 centers across the country to receive follow up drops, he said.

The children also will be given Vitamin A and de-worming tablets on Sunday, he said.

The government started the program with the help of the Global Polio Eradication Campaign _ a partnership among UNICEF, Rotary International, the World Health Organization and the U.S. Centers for Disease Control and Prevention, according to the ministry.

UNICEF and WHO helped Bangladesh conduct extensive polio vaccination programs in 1995-2004, and the country's last case was thought to have occurred in August 2000.

But the country's efforts to be declared polio-free were thwarted when 9-year-old Rahima Akhter was recently paralyzed by the P1 polio virus in the eastern district of Chandpur. It was not clear how she was affected, but the same P1 virus has also been found in parts of neighboring India.

Polio spreads when unvaccinated people come into contact with the feces of those with the virus, often through water.

The virus invades the nervous system and can cause permanent paralysis within hours. It also can be fatal in some cases.

About 1,880 people were sickened by polio worldwide last year, down from more than 350,000 before 1988, when WHO launched a global anti-polio campaign, according to the agency.